Gardening Is Full of Gardening Myths, Folklore, Old Wives Tales And Misconceptions That Need Debunking. Here’s The Truth About Gardening Myths
I’ve spent most of my life as a market gardener, farms manager or amateur gardener and I’ve heard so many gardening myths, legends, folklore and worse. It’s as if gardeners believe they must set themselves a Herculean task list that they must complete before being accepted into the gardening fraternity. This fallacy is often perpetuated by other gardeners that maintain the stories because they have never bothered to check the facts themselves. In fact, it’s often hard to discover the truth as some books also perpetuate these gardening myths., without any evidence except the author also read it in a gardening book!
So much gardening “accepted wisdom”, and “accepted wisdom” from old gardeners is simply wrong and this post sets out to expose the myths, explain why they are myths and get the facts explained.
Of course, there are old gardeners with great wisdom. But they are the ones that rely on facts, and not myths, to run their gardens.
The Watering Outdoor Plants in the Sun Scald the Leaves Myth
This is a myth that seems to be repeated on social media all the time when we get hot days. People are convinced that watering plants, or even rain falling, on plants during hot weather will scorch the leaves. With so many websites also perpetuating the story I can understand why newbies believe it.
It is of course another gardening myth .. but how can I convince those that have read such horror stories from gardeners that swear its true.
Let’s start by looking at the logic. The belief is that the water droplets sitting on plant leaves act like a magnifying glass and burn the leaf.
Can you remember as a child using a magnifying glass to try to start a fire? Lots of kids did it. They held a magnifying glass a few inches away from a pice of paper or other computable material and focused the sun into a single point. This increased there temperature, usually resulted in scorching, sometimes saw a plume of smoke rise and on very hot days resulted in a flame.
So thinking that water droplets can act like magnifying glasses starts to make sense. But does it?
There’s a difference in setting fire to paper and scorching a plant. And I mentioned it above.
Why Water Droplets Don’t Magnify The Sun Enough To Scorch the Plant
The difference is in that one small fact that to focus the heat through the lens we need to hold the magnifying glass a few inches above the computable material.
If you leave a magnifying glass lying flat on a piece of paper it doesn’t focus. So it can’t burn.
Of course if we were to leave a bottle lying on its side or even stood up in dry grass it might act as a magnifying glass and cause a fire. But that’s because it isn’t in contact with the combustable material.
When a leaf has water droplets on it it is far more likely to cool the leaf as the water evaporates.
Of course if you leave a hosepipe lying in the sun and then squirt water from it over plants they will scorch. Water in a hosepipe can get very hot and if sprayed on a plant will “cook” it in moments. But that’s a different thing.
Watering Wilted Plants
If a plant is severely wilted it isn’t a great idea to poor cold or even warm water on it. It would be a bit like you being thrown in a pool of freezing water on a hot day. Not at all pleasant and likely to shock your system. With people, in the extreme, it cause a heart attack. and we don’t want to give our plants the botanical equivalent of a heart attack.
If plants are wilted water them from the base. Get the roots wet, not the leaves. And pour water on pathways etc. to cool the atmosphere.
Another reason not to water when the sun is shining is that a lot of the water will evaporate and not get down to the roots.
Ditto watering in very windy weather. Water gets blown away and evaporates. There’s little sense in that. It’s far better to water early morning before the wind gets up.
Plants left wet overnight are more likely to succumb to fungal diseases. So that is often frowned upon as well. Having said that, I always watered outdoor crops overnight with an automated raingun. It was still the best option.
As for indoors, in greenhouses and tunnels, I always tried to water early morning so the plants had time to dry.
Whatever method of watering you choose, remember this one thing. Water on leaves doesn’t act like a magnifying glass. It’s another myth.
The Vegetables Need Starting Early in a Greenhouse or on a Windowsill Gardening Myth
This is one of those myths that seem to have been started by impatient people. Most veg are quite happy being sown outdoors in due course and some can be sown well before the risk of frost has passed.
True, warmth loving plants, such as tomatoes, cucumbers, melons, aubergine, chillis and peppers can be sown early and benefit from a propagator or warm windowsill. But most vegetables are fine without being forced like hothouse plants. They can be sown outdoors without mollycoddling indoors for months. that’s not to say that starting in modules isnt to be practiced, just that starting crops indoors is a choice NOT a necessity.
Indeed many crops are quite happy with cold weather, frost and even snow. So we can happily sow parsnips in February or March in my part of Devon and starting in modules just leads to contorted roots. And broad beans sown in November doing very well, maturing before “black army” (black aphid) become a major problem. I do however advise not sowing earlier or they will be too big going into the winter and will flower in early winter … and that’s not a great idea.
As for crops such as carrots, beetroot and other “small seeds” sow them outdoors in spring. I can start most of these outdoors in March but of course some regions will be later than this due to being further north or at higher altitudes.
Will The Frost Damage Early Crops?
The fear of frost damage prevents many gardeners, new or well established, from sowing or planting out too early.
When I grew lettuce and celery outdoors on my market garden in Bedfordshire (not the warmest county in England), we would plant them outdoors in mid-March. Some we would cover with fleece to speed them on their way to an earlier harvest. Others we would leave open to the elements. This often meant open to frost, wind and snow.
I’ve seen crops of lettuce and celery where the leaves were killed by the frost or dried up by a fierce frost laden drying wind. It looked like the plant was dead and in many cases the leaves were actually absent, having dried up and blown away. But, as the weather warmed and the late winter winds dropped, small leaves would appear and the crop would grow to maturity as if nothing had happened.
The surviving crop wasn’t poor quality and was sent to the supermarkets with their draconian high quality standards (except when there’s as shortage when standards mysteriously drop!).
Starting crops indoors can actually delay plant maturity and harvest as can be seen from sweetcorn cultivation. Sweetcorn and farm grown maize (grown for cattle silage where the high protein levels are a homegrown substitute for soya meal) are cultivars of the same species. Gardeners often start sweetcorn indoors and grow them on in pots etc until it’s warm enough to plant them out. By this time they have plenty of roots but ar often potbound!
Maize however is not sown until the soil is warm. At college I recall a lecturer saying the soil was warm enough for maize sowing when he could drop his trousers and sit comfortably on the soil! But cast away that graphic image for a moment. Maize is usually sown in early June. The image on this page is of farm grown maize just 3.5 weeks after sowing. It’s grown at a phenomenal rate. And, as I write at the end of June it is growing an inch a day. In just a few months it will be two metres high with mature cobs and ready to be harvested and ensiled for the dairy cattle.
The point is that most sweetcorn, sown and grown indoors before transplanting, will be behind this crop before long. Drilled (outdoor sown) crops, sown in ideal conditions, grow faster than the forced crop.
Sweetcorn also has the advantage that it matures earlier than maize. So even if not sown outdoors until late May, or early June, sweetcorn could be ready for harvest in as little was 60 days. Even the longer maturity types are ready in 100 days. And being sown and grown in better conditions, the crop often has more cobs per plant.
The “Cut The Leaves Off, It’ll Grow Better” Gardening Myth
Gardening Myths abound and I see this one so often in summer. Usually it is about tomatoes but there are variations that include cucumbers, courgettes, melons and other plants with large or densely packed leaves.
Let’s start with the basics. Plants have leaves for a reason. If they were of no use to the plant they wouldn’t grow them or would naturally shed them like deciduous trees do in autumn.
What About Sideshooting & Deleafing Tomatoes
Let’s start with tomatoes and their need for leaves. Tomatoes need their leaves to photosynthesise and produce the sugars and starches etc that allow the flowers to bloom and the fruit to grow and swell. The confusion about the need for leaves is twofold.
Firstly, indeterminate tomatoes are grown as cordons by removing their side shoots. This then leaves a single stem from which leaves and flower trusses grow. Sideshoots aren’t leaves, they are shoots that comprise a stem, leaves, flower trusses and subsequently fruit trusses. In fact, they are fractal-like in that sideshoots also produce sideshoots of their own. This is how bush tomatoes are formed. The main difference here being the bush tomatoes are naturally determinate and don’t keep growing upwards … they terminate with a flower truss and all addition growth is via the sideshoots.
But I digress. Sideshoots are not leaves .. though one guy on Facebook told me there was basically no difference as sideshoots had leaves on them and were therefore leaves. Botanically he’s wrong, and hence removing sideshoots is not the same as removing leaves.
The second area of confusion is that tomato growers are advised to remove leaves from the main stem to aid ripening. This doesn’t mean removing all the leaves. Let me explain.
The idea is based around the fact that tomatoes ripen better in warm temperatures rather than cool ones. And if a tomato plant has dense leaves covering the fruit they remain cooler and don’t ripen so fast. So we remove the leaves from the main stem at a certain time in the growth cycle. But not all the leaves!
It works like this. Once a truss of fruit starts to show a bit if colour, often a faint orange (or whatever other colour toms you choose to grow) you remove the leaves up too that truss and no higher. This allows the sun and light to get to the fruit and warm them enough to promote ripening. Don’t take off any more leaves at this stage.
Once the second truss starts to show colour remove the leaves to that level and no further. Repeat as the successive trusses start to show colour. It’s that simple.
Removing Leaves From Courgettes
I see a lot of people advising the removal of leaves from courgettes “to make them yield more”. I’ve grown courgettes commercially and it doesn’t work like that. Removing leaves reduces the plants ability to grow. And, frequently, if you remove leaves the next thing the plant tries to grow is another leaf. Why? Because it needs leaves to produce the fruit. So removing leaves just takes energy that would have gone to growing fruit bigger and uses it to produce more leaves.
I sometimes see it argued that large leaves shade the fruit and stop them growing. Yet I see no evidence or research on this. And leaves aren’t static. During the day they move to catch as much sun as they can. They do this as the more sun the get the better they photosynthesise.
Leaves are actually marvellous structures that follow the sun and align themselves to maximise the interception of sunlight. Remove them and you are assured of a poorer crop.
People often say “I’ve done it this way for 40 years and get good crops”. They think this justifies what they do. Of course it does if they are satisfied with their yields. But after 40 yers of doing the same thing I wonder if they really know what a good yield looks like. I’ve seen so many people harvest 30, 40, 50% of what they could have, for the same amount of effort, just because they did the same thing for 40 years and had never seen a good yield.
Dead, Diseased and Dying Leaves
Let’s not be totally naive. There are times when leaf removal makes sense. If a leaf is diseased there might be a case to remove it. Note I say might. In the case of mildew on cues and courgettes, removing the leaves makes very little difference to the progress of the mildew which is airborne. In fact removing leaves might even spread more spores!
Leaf removal will make the plant look aesthetically more pleasing, but it’ll make little difference other than that.
There might also be a case for removing a few leaves to help harvesting. If we can’t see the crop we can’t harvest it. But the cost will always be yield reduction. Occasionally, with a greenhouse crop of courgettes, where growth has been rampant, I’ve reduced the leaves a bit. But this was a rare event. Most years I didn’t. And it only ever happened at the end of a cropping period, When growth was rampant and yield tailing off. Most of the time I wouldn’t dream of it. The advice I give and followed 98% of the time was don’t remove leaves from courgettes.
Exceptions To The Rule?
If you grow pumpkins you’ll know they just keep growing and the vine will get longer and longer. And, if once you have 3-5 pumpkins on a plant you want then to grow big then it makes sense to stop the plant. This is done by removing the growing tip of the stem.
We follow this idea with tomatoes as well. When the crop reaches the top of the greenhouse then it’s time to stop them So we remove the growing tip of the stem.
This is NOT the same as removing leaves. But some gardeners think it’s the same. It isn’t. Botanically it is totally different.
More Gardening Myths Below
The Potatoes Need Earthing Up Myth
There’s a gardening myth that says potatoes need earthing up and I want to examine it and get the truth.
Amazingly, even sites such as the RHS repeat this myth.
Farmers always earth up their potato crop and that’s where the myth starts. As a farmer and grower I used to earth up potatoes. But not for all the reasons I see given online. Farmers earth up potatoes mainly because it makes mechanised harvest much easier.
I’m not saying that there aren’t times when earthing up can be done, I’m saying it isn’t strictly necessary and this insistence that they must be earthed up is a myth.
Getting Back To Potato Basics
Potatoes come from South America. They’ve been improved in terms of yield a lot since they were first brought to Europe but fundamentally they haven’t otherwise changed much.
And in their home, in the Andes, where they grow wild, no one goes around earthing up potatoes. Nature doesn’t work like that. They grow perfectly well without all this gardening fuss we now make of them.
Why Earth Up Potatoes?
Other than making mechanical harvesting easier all the reasons for earthing up potatoes are for our convenience, not for the potatoes.
Earthing Up For Frost Protection of Potatoes
Potatoes are frost susceptible so many people plant and then earth up when frost is forecast. This cover susceptible leaves and protects them until they grow through the soil or compost.
Farmers don’t do this. They plant a bit later and don’t get potatoes above ground when frost is threatened. And if there’s a late frost they just accept the plant is knocked back a bit but will regrow.
However, if you want to grow a really early frost there are methods other than earthing up you can use. For example, put fleece over the crop. It breaks a light frost and the crop survives.
Don’t forget potatoes need leaves to produce the tubers. It’s where they convert plant nutrients into everything needed to form the tubers. And if you keep covering the leaves up they can’t do their job. And destroying the leaves doesn’t make much sense really.
Earthing up Potatoes to Stop Them Going Green
Potatoes go green if exposed too long to sunlight. So people earth them up.
Nature never earths them up. And if you plant the crop sufficiently deep they don’t come through the surface and get exposed to the sun.
Tubers are grown from the potatoes roots. Roots grow downwards due to geotropism. Roots never grow upwards from choice. So if the plant is grown correctly the roots go down and the potatoes from underground. They don’t get exposed to sunlight and don’t go green.
If however you plant the tuber too shallow, heavy rain can wash away the soil from the tuber and it might go green. The answer is to plant deeper.
And don’t forget, if you earth up soil it is more likely to get washed down by rain than if it is on a flat surface .. ie not earthed up.
Earthing Up Potatoes Gives Longer Roots and Higher Yields
If this were the case don’t you think farmers, with their huge tractors and machines, would earth up once the crop is growing rather than as they plant?
In the garden, if you want longer roots, plan deeper.
Earthing Up Potatoes to Control Weeds
Old farmers will tell you that if you plant potatoes “on the flat” you can earth up later to control the weeds. Farmers that earth up as they plant control weeds with herbicides. But before they were available farmers planted and earthed up as the first flush or weeds appeared. Sometimes they either up a second time as this acted as a form of combined hoeing and earthing up
Container Grown Potatoes
So far I’ve dealt with growing crops in the soil. But of course many of use grow potatoes in large containers or bags. In these situations you can decide which method to choose. Personally I’m a “lazy” or efficient gardener and do no more than I have to. So I fill the container with compost and plant deep. Job done. No extra work later. No extra compost needed. Simple and easy. It gives me bumper crops.
No Dig Potatoes
You might think that potatoes can’t be grown in the No Dig garden. It’s not true. they can be .. and without earthing up or digging.
Firstly take a trowel and make a very shallow depression in the compost. Place the seed potato in it. Now cover the potato with compost OR grass mowings.
That’s it really. It’s that simple. To harvest just remove the grass mowings or compost (it can be recycled).
You might see a flaw in this system. The grass mowings will dry out and expose the growing tubers .. and that is a reason to earth them up! Wrong.
Just add more grass mowings as they dry out. What you are doing is a sort of earthing up to keep sunlight out … but it uses old grass. When I grow them this way the grass heap sometimes get to be 12-15 inches high. So it resembles earthing up, but it earthless.
I’m not saying never earth up. It can make harvesting a bit easier if potatoes are grown in the soil. What I’m saying is that its a myth that you MUST earth up. It’s a choice, not a necessity.
More Gardening Myths Below
The Trees Should Be Planted in Square Holes Myth
I’ve seen so many people write about this and explain that research has shown that trees need to be planted in square holes to stop the roots going round and round the hole.
Logically when the roots go round and round the planting hole loads of problems will ensue. They will fail to find enough water, never get enough feed, and without a good well spread root system the tree could easily blow over in the wind. That makes perfect sense doesn’t it. Surely everyone can see this and will never try to plant a tree in a round hole ever again.
Except of course its a total myth. Try Googling the research. You’ll find plenty of experts repeating the need to dig a square hole. But you’ll not find any verifiable research.
The reality is that roots are tough little blighter. Plant a tree in a paved area ant they push up the pavement in a few years. Plant a tree in the soil and whatever shape the hole is the roots will force their way out of the hole into the adjoining land. It’s what plants do. They need to stretch out to ensure they have a good root system the anchors them when there’s a storm. And they need to get out to ensure they can reach water and plenty of nutrients. As I say, it’s what trees do (as do all plants).
The only exception is where a tree has been left so long in a pot that is become potbound and the roots have coiled around the pot. But that’s not a problem associated with the hole shape.
When a tree fails and is dug up and the roots are circling the planting hole its 99.999% certain it was down to the pot bound problem.
If you have a pot bound tree that needs planting try to tease the roots out a bit before planting. It’ll make a huge difference and probably save the trees life.
And if you ever see a story about tree plating holes needing to be square do a Google search and look for some evidence of the research they are almost bound to quote. I bet you can’t find any genuine research.
More Gardening Myths Below
Garden Crop Rotation Myths
I regularly read about the need to rotate crops. Lots of experts write about, and recommend a three-year rotation, others recommend a four-year rotation. A few recommend a seven-year rotation and I’ve even seen a ten-year rotation advocated.
So my first question is, if rotations are so important, why can’t the experts agree?
Why Should We Rotate Crops?
My next question is why should we rotate crops? The answers seem to include the “fact” that crops deplete the soil of goodness, of vital elements, and needs resting between crops. In fact, some rotations even recommend we should cease growing anything at all some years and let the land lie fallow.
Another reason given is to prevent a build-up of soil-borne diseases. So I have to ask if that works on a garden scale.
Let’s apply some logic to these “facts”.
If plants depleted the soil of vital nutrients I wonder how places such as the Amazon rainforest continues century after century. Surely the growth of huge trees would deplete the soil of nutrients and the trees would be unable to grow. But the fact is the trees in the rainforest keep growing.
On a garden scale, how does that work? Say we grow a hungry crop of potatoes or leeks. What gets depleted from our soil? Let’s assume it’s called X. How do I replace it? Will growing another crop from another plant family replace it? Because if not I’ll never be able to grow leeks or potatoes there again as the soil will remain depleted. And if the deficiency is replaced where did X come from?
And what about soil-borne pests?
On the assumption that soil-borne pests are specific to certain crops (some are), how many years before they die out?
And if they are soil-borne, will we spread them on our boots and tools? No one seems to warn about that.
The reality is many soil-borne problems are spread in this way! So why does no one warn gardeners that it’s part of the rotation process?
Decomposition Is The Key To Growth
In the Amazon, trees grow, get old, die, fall to the ground and decompose. The decomposition releases nutrients which then feed the next generation of trees. This is the secret of crop rotation. The Amazon doesn’t need different trees or to lie fallow for the odd year. It’s a continuous process. A closed-circuit process.
That’s how it should be with our gardens.
Our gardens are slightly different in that we remove some organic material and eat it. So we need to replace it with compost or fertiliser. It’s that simple.
If we apply a good cover of compost each year OR add some fertiliser that will keep the nutrient level at the right levels and crops will grow. That means we don’t need to rotate to because the soil becomes nutrient deficient.
As for soil-borne pests and diseases, they can sometimes become an issue if we grow the same thing year after year. But only sometimes, in fact, rarely might be a better word to use. I’m not an advocate of monoculture, wheat prairies or similar. But growing the same crop on the same land isn’t normally a problem as my fellow grower Charles Dowding has demonstrated. Charles has grown potatoes on the same spot for seven years with no problems. Each year he has meticulously weighed every gram of harvested crops and can verify his success.
He does of course grow more than one crop on the land each year. His following crops might be leeks, cabbage or whatever before growing potatoes again the next year. But each year he grows potatoes on the same spot with no issues.
What Charles and I do, is to add plenty of compost to our soil each year. That deeds the soil with nutrients and there is no nutrient depletion. The compost also feeds the soil fungi and other soil microfauna. Healthy soil doesn’t suffer nutrient depletion.
History Proves Rotation is Necessary
Advocates of crop rotation point to history and explain that our forefathers rotated and how they knew a thing or two. They talk about the Norfolk Four Course Rotation principle and other farming methods.
Of course, our forefathers did know the land better than many of us today and farmed in the best way they could. But since then we’ve learnt a lot. In their day they grew wheat, turnips, barley, and then a year of clover or grass. They didn’t have a fallow year. And they added fertility by grazing the turnips with their sheep. And the grass crop was for sheep and or cattle. That added back animal droppings. Plus the clover added nitrogen via nitrogen-fixing bacteria. As a farming method, it worked. In its day it was seen as being intensive farming.
But of course, it was far from intensive and yields were meagre compared with what we want from our land today.
And we can add our compost from compost bins and bought-in compost from farms, stables or wherever. Our gardens can be far more productive than farms that used the Norfolk Four Course system.
Market Gardening Experience
When I had my market garden I grew highly productive vegetable crops outdoors and many were grown on the same land for ten years or more. For example, we’d grow between a quarter and half a million lettuce a year outdoors. Some years each acre of the field grow two crops of lettuce. And next year did the same again. We didn’t get nutrient deficiencies because we fed the soil with good organic fertilisers and farmyard manure. For example, where I was growing celery I would put six inches of pig manure on the soil in early winter and then plant the crop there in March. It retained the moisture (celery is a marsh plant) AND provided nutrients. The next year I would move that crop, not for rotational purposes, but because I wanted to put manure on other parts of the field.
In all the years I ran my market garden we never suffered from any form of nutrient deficiency and we never rotated the outdoor crops. As for crops grown in the greenhouses, we would grow as many as four crops of lettuce in a greenhouse in a single year (intensive is where you grow six crops of lettuce a year). We had no problems. But maybe because every two years I added an eight-inch layer of spent mushroom compost. Coupled with the use of organic fertilisers we had all the nutrients we needed. We never rotated our crops. It’s unnecessary.
There are a lot of people out there saying crop rotation is necessary. And whereas it does no harm it really isn’t necessary for gardens, as people like Charles and I have understood for years. Why make growing more difficult than need be.
What we also need to remember is that most of the research into rotations have been focused on agriculture. Agriculture is a lot different to gardening.
Last word .. I have one last proviso on the above. IF you have a bad case of soil-borne disease such as sclerotinia then rotation is necessary. But these cases are rare. I only saw sclerotinia* once in all my years of market gardening. Then we clamped down and didn’t grow vulnerable crops on that ground. We planted it to grass and grazed our goats on it. That way the problem couldn’t be spread on tractor tyres or boots. And the grass-clover mix made a contribution to the soil fertility .. plus we had plenty of good milk to make goat’s cheese with.
*But even sclerotinia isn’t as bad as often painted. It’s a disease of herbaceous plants grown in wet col conditions. So if you choose the right crops, grown in summer, it’s not going to be a significant problem.
More Gardening Myths Below
Believing What “Experts” & Old Joe Say
The biggest reason myths exist is because people believe what they are told by “experts”, without question. You know the sort of people that give advice on allotments, over garden walls and even on the TV.
OK so when we are new we seek advice, and Od Joe has had an allotment for years so he must know what he’s doing. And his crops look good and he’s always there to tell you what you are doing wrong.
The problem is you’ve only Old Joe’s word that he knows what he’s doing. Sure he has some crops and they are not too bad. But you are new, so would you actually know what a really good high yielding crop looks like? I’ve frequently seen people claim to have great crops of tomatoes, then they see mine and say my crop and ask how I do it. At that time I often think to myself, “this isn’t a great crop, it was much better last year”.
It’s a bit like the four-minute mile. For years the world believed it was impossible. Then, in 1954, Roger Bannister broke the four-minute barrier. And soon afterwards several other people ran the mile in less than four minutes. Tomatoes are the same. Until you’ve seen a great crop you don’t know what’s possible.
It Was On The TV
There’s another sort of expert. The TV presenter.
Let’s start with the good ones. Some are very good. They have years of education AND practical experience and really know their stuff. Then there’s the TV presenter that learnt it from a book. You see them in their TV garden and they give all sorts of advice. What you don’t see is the gardening crew that maintain the garden when the “expert” isn’t performing to camera.
And don’t be fooled by their books. In many cases, they didn’t write them. They had a ghostwriter do it for them. How do I know? Well, when I worked in horticultural colleges we used to get TV presenters advertising “research” jobs to students. The research was then often published after a professional editor had polished it, as the presenters own work!
The thing is not all experts are as expert as they think.
What sort of gardening myths do experts spread?
The answer is pretty much every gardening myth ever told.
It works like this.
You all know I know a lot about growing salads, veg, herbs etc. And you are having slug problems and I tell you I have the answer. The chances are you’ll listen to me.
The truth is I used to have slug problems but the slugs disappeared nine years ago. It was the year I started parking my bike outside the greenhouse. I’ve ridden that bike ever since, parked it outside the greenhouse every day and never had a slug problem since. Personally, I put it down to the fact I squash a lot of slugs with the tyres and that has got rid of the slugs. Those that survived realise how dangerous it was to stay and left my garden.
If you are naive enough to believe the bike story makes sense then you really should read my slug advice and watch the videos in it. In the videos you see slugs crawling over eggshells, copper .. and all the other mythical slug solutions.
If any of these have worked for you, I’m pleased. But it’s not that sheep’s wool, copper or eggshells work. It’s probably down to some other reason. Things like the hedgehogs that come every night. The fact it’s been extra dry. Or maybe it’s the increase in ground beetles predating the slugs.
It’s the same for loads of other myths. For example the Flower Pot Heater myth. I cove this one later on this page but in brief, it goes like this. People burn a candle or two in a greenhouse to keep the frost out. It works perfectly when the nights are arm but fails when it’s really cold. If it was a great way to heat an area why don’t you burn candles in your home?. It would be cheaper than the boiler and central heating system.
The thing is a candle gives out around 30 watts of heat and you need several thousand to heat a small house. It’s as much a myth as my bike killing slugs.
The Science Bit
The only way to prove something works is to do it the scientific way. You need to test your ideas against a control. Use eggshells around some plants and not others. See if there a difference. But don’t do it once. The results from one experiment could be down to luck. Do it dozens, maybe even hundreds of times.
When scientists test these things they would also test them in different parts of the country, under different conditions. It can take years to do it thoroughly. But once they have replicable results, you can be reasonably sure what does and doesn’t work.
One thing is certain. Old Joe, probably hasn’t ever tested anything as thoroughly as he should have before giving adamant advice.
Advice That Applies to Another Continent.
Lastly, let’s consider the advice that is both totally correct and totally wrong at the same time. For example, I recently saw someone advising that we needed to mulch tomatoes to stop tomato blight. I queried it as after years as a commercial tomato grower this was news to me.
The writer came back and referred me to a university website where the advice was given. 99% of gardening/growing advice on university sites is good advice. So why was this bad advice?
Simple. It was on an American university site and referred to early blight on tomatoes in the USA. We don’t get early blight in Europe. We get late blight. They are totally different diseases with a similar name. So, though it was good advice in the eUS it was bad advice for UK growers. Totally wrong as mulching isn’t going to help us when late blight is airborne!
More Gardening Myths Below
The Candle & FlowerPot Heater Gardening Myth
It’s the time of year for The Candle & FlowerPot Heater Gardening Myths.
It goes like this. On frosty nights greenhouses can be kept warm with a handful of candles left burning under a terracotta flowerpot. If the choice is between the frost killing those tender tomatoes or being kept at bay we naturally want to warm the greenhouse and stop our plants from dying.
And let’s face it anything that burns gives off heat so this ought to work .. shouldn’t it?
Correct, burning produces heat. But the idea a few tea candles can protect a single glazed greenhouse is still 99.9% myth.
Think about it logically. If candles were that good why do you have a boiler or other heat source in your home? Surely a few candles would do? After all your home is presumably insulted and draught free compared with a single glazed greenhouse that has no insulation. And even if you’ve added a layer of plastic or bubble wrap, just how much heat retention does that give? Try wearing a layer of plastic instead of clothes on a cold day .. do you think that’s going to keep you warm?
The reality is that a candle gives off about 30-40 watts of heat. A one-bar electric fire or fan heater gives off 1000 watts .. or 3000 watts if you run three it at maximum setting ie 3 Kw. So you need around 100 candles to give as much heat as a fan heater. And the candles will not burn for many hours so probably need replacing at least once during the night.
The Science Bit: The Candle & FlowerPot Heater Myth – denying Another One of Those Gardening Myths
Advocates for the candle idea point out how hot the flower pot get when the candle has burnt for a while. And they are right. It gets hot .. and it radiates heat. It’ll certainly be too hot to touch. But stand a couple of metres away and it’s going to be much colder.
The first law of thermodynamics is clear on the subject. It’s about the conservation of energy and says the energy in a system remains constant. That means when you add the flowerpot it cant add more get. it just retains the heat from the candles. The flowerpot doesn’t add extra heat to the greenhouse. It just traps it in one place. So the heat is at the level of the flowerpot rather than rising into the roof space. However, there is very little heat added to the greenhouse.
People Say, It Works For Me!
I’m expecting a lot of people to say I#’m talking rubbish and the candle and flowerpot trick works for them. That’s great, keep doing it.
But the reality is that if you didn’t get frost in your greenhouse it was because it wasn’t that cold and toms tolerate a few hours at 0C or even below. I often stand a few buckets of water in the greenhouse and it’s equally as effective and costs nothing. The reason is that as water starts to freeze it gives off latent heat. In other words, the act of freezing produces what is called the latent heat of expansion. And that is often enough to enable my toms to survive.
If you also use a layer of fleece that will break a mild frost as well.
So if you want to carry on using candles, please do. Provided they don’t start a fire and produce toxic fumes as they burn that’ll be fine. But I’m not going to bother.
I’m also going to avoid heating my home with a few candles .. it’s never going to work. Unless that is, you can prove that the laws of thermodynamics are a myth. I’ll nominate you for a Nobel Prize if you can.
More Gardening Myths Below
Plants Must Be Watered From The Bottom
I hear this so often in reference to tomatoes, cucumbers, lettuce and many other crops. I challenge it by asking why plants need watering from the bottom. I’m often told it’s because the water damages the leaves and the plants will die.
That’s totally untrue.
If water damaged the leaves of plants such as tomatoes how do some people grow them outdoors? Surely they’d all die when it rained? The U.K. is known for its rain, but many of us grow tomatoes outdoors. If wet leaves killed plants that wouldn’t be the case.
When I grew tomatoes commercially I used to hose them down every day from the flowering stage onwards. This was the way all commercial growers pollinated their tomatoes. They didn’t die after getting wet. They thrived on it.
So clearly the wet leaves idea is another gardening myth.
Can Water Damage Leaves?
This is a different question altogether. I’ve seen tomato plants badly damaged by the incorrect use of a hosepipe. My pollination method is downright stupid if done incorrectly. A hose left on the ground in strong sunshine gets very hot. When turned on the first water out of the hose can be extremely hot. If it gets on the leaves it will cook them! They will die!
But cool water is fine.
If plant leaves get wet early in the day they will dry before dark. Get them wet late in the day and they will stay wet all night and this could lead to fungal diseases.
Wet Lettuce Leaves
When lettuce are grown in greenhouse borders the usual way they are watered is by overhead irrigation. It’s the nearest thing to rain we can simulate in greenhouses. The leaves get drenched.
This isn’t a problem if done early in the day. Leave it until the full heat of the sun is on them and drench them in cold water and they’ll not thank you for it. Some leaves, or at least parts of them, may well suffer from necrosis. As this plant material dies it’ll often be the source of fungal infections and the plant will die.
But death was due to poor watering practices not watering per se. If you have 50,000 lettuce in a greenhouse there’s no way you can water each one from the bottom. Overhead irrigation is essential.
The above advice applies to the crops specified. It’s also true that a few species of plants dislike water on their leaves and others are adapted in such a way as to gather water on their leaves and funnel it to the roots. These situations are different but don’t change the fact that wetting the leaves of crops such as lettuce and tomatoes is fundamentally fine.
One last thing about watering. Watering little and often is generally a bad idea. It keep the roots near the surface whilst in most cases we need them to go deep in search of water and nutrients. So my crops of lettuce were usually watered once a week or thereabouts depending on the weather (in winter they could go months without being watered). But thirsty plants such as tomatoes and cues were watered every day and would each consume around half a gallon of water a day.
More Gardening Myths Below
Don’t Plant Anything Before The Last Frost – More Gardening Myths?
I see so many warnings about not planting anything outside before the last frost and it’s such bad advice.
Because many plants are frost hardy and survive frost. In fact, some need the cold to be able to produce seed and start seasonal growth. Just look out of the window. You will see grass growing, and as I write this I can see plenty of spring flowers in my garden. There’s cherry blossom and the magnolias are looking incredible. On the hillsides near my home, the oilseed rape is coming into flower and the corn is growing.
So clearly many plants have no problem with frost, snow, ice or torrential rain. Over millennia they have evolved to cope with it.
Of course, some plants need more warmth. Plants such as tomatoes, cucumbers, courgettes, melons and other plants of the Cucurbitaceae and Solanaceae families need warmth and are killed by frost. Ditto most of the bean family. Barring broad beans that is. They usually survive very severe weather.
When I had my market garden we would grow our outdoor lettuce and celery in blocks (modules). We germinated them in the greenhouse but then, once they had a couple of true leaves, we planted them outdoors. My first planting was usually 20,000 celery and 80-100,000 lettuce. They would go outdoors in mid-March most years and would see a lot of frost, and often snow, before harvest time in late April mid-May for lettuce and July for celery.
About 20,000 lettuce would be covered in fleece to bring them on a bit earlier. But the majority had no protection whatsoever. And they lived AND grew into high-quality lettuce for the wholesale markets and major supermarkets.
Other crops that cope very well with frosts include beetroot, spinach, onions, leeks, shallots, salad onions, peas, broad beans, radish, cabbage, kale, broccoli, carrots .. there’s a long list.
Please note, I’m not advocating you plant temperature-sensitive plants. Things like bedding plants are largely frost-susceptible, as are temperature-sensitive species such as dahlias.
Adding Sand to Clay Soil Makes It Free Draining
More gardening myths?
Gardeners soon learn that clay soils are fertile but very poor draining. And because sand is very free draining they believe the myth that add ing sand to clay soils will aid drainage.
It doesn’t. It frequently makes things worse for the plants. Here’s why.
Clays soils vary a lot but in all cases, they are made up of very fine clay particles that sit closely together. So close together that even water struggles to drain through them. If you are very lucky, you’ll have a thin layer of clay over a well-drained subsoil. In this case, the problem isn’t too serious. Plant roots can penetrate down through the clay into the subsoil below where it is drier and there’s a bit more air (they need air).
But in many cases, the clay is very deep. It might go down hundreds of feet into the ground and drainage is always going to be an issue. Bear in mind that clay was “puddled” to line canals or village ponds, it is that good at retaining water. And puddling is the process of smearing the clay to make a non-porous layer through which water can’t go. It’s what happens when we abuse clay soils by ploughing, rotovating or even walking on wet clay soils.
But what about adding sand to clay soils?
Imagine you have a bucket of heavy clay soil and you add a few handfuls of sand. Now imagine mixing it together. The clay is wet, cold and heavy. It isn’t going to be easy. It’s going to require a huge effort to mix it thoroughly.
Now consider each grain of sand. If they are spread evenly through the bucket what is it going to be surrounded by? The answer is obvious really isn’t it? Each grain of sand is surrounded by cold wet clay. Is that going to be more free draining?
The reality is we’d need to add at least 30% soil to clay to make much difference. And if below that are hundreds of feet of more clay there’s nowhere for the soil to drain and all we’ve done is create a sump in which the water can sit. And that will drown our plants more surely than if it were all clay.
The Raised Bed Necessity Myth
More gardening myths?
I see many new gardeners posting that they’ve made a start on their garden by building raised beds. The next question they ask is what do people fill their raised beds with as everything they’ve looked at costs a lot of money. And it true, just Google screened topsoil and you’ll see bulk bags of topsoil costing around £80 delivered.
The thing is, a new gardener, or any other gardener, rarely needs raised beds. That’s not to say there is no place in gardening for them. If you want to garden in an area that is presently concrete, then a raised bed might make sense. Or if the soil is full of debris or your garden has exposed rock or rock within inches of the surface, then a raised bed could make sense.
And if you are in a wheelchair or have a very bad back then raising the soil level makes a lot of sense.
I’m not against raised beds when the conditions or your health dictate its necessary. What I’m concerned with is the myth that we are not true gardeners unless we have raised beds! That myth is that raised beds are necessary for good healthy crops in every case.
What Nature Needs For Healthy Crops
In nature plants need light, moisture, nutrition and a few other things but nowhere in nature do we find the necessity for raised beds. No one built raised beds as a necessary part of the Amazon growing. The trees survive perfectly well without. The great grasslands of Africa, the jungles of Asia and the northern tundra are rich, biodiverse biomes that grow billions of tons of plants without the need for raised beds.
So why do we think they are so necessary for a garden or allotment? We do we spend so much money on raised beds before we have bought a single seed or any compost, seed or tools?
Of course, I don’t expect everyone to agree with me, and it is for all of us to decide on how we wish to garden. But after decades as a commercial grower, lecturer and gardener I’m still amazed at the persistence of the Raised Bed Myth. And I’m saddened that it is still perpetuated by some gardening magazines and gardening presenters!
So let’s examine the pros and cons of raised beds.
Raised Bed Benefits
Raised beds decrease soil compaction because you don’t need to stand on the soil. And of course, this is perfectly true. But its also true that No-Dig is another cultivation method where gardeners don’t compact their soil by walking on it. And No-Dig doesn’t cost a fortune in buying or building beds and adding a huge amount of compost to bring them up to the required level. All No-Dig needs is a small amount of compost put on the soil each season. No more compost than many raised beds need as they sink each year.
Raised Beds don’t need digging. Nor do No-Dig beds!
Raised Beds look nicer. Agreed they do look nice if made from high-quality materials. They can be painted as well. I understand why a nice looking garden is important to some people. It is to me. But raised beds aren’t the only way to produce a clean tidy garden. Many gardens without raised beds look very tidy and can look extremely good at a fraction of the cost.
Raised Beds Prevent Slugs, Snails and Other Critters. I disagree. I hear from a lot of raised bed gardeners complaining that slugs and snails are attacking their plants. In fact, slugs and snails love raised beds as it gives them somewhere to hide and overwinter!
And though hedgehogs can climb, they are often deterred from climbing on to raised beds and don’t predate the slugs and snails the raised beds encourage.
As for critter such as deer, they love the idea of raised beds. It means they can graze your crops without bending over!
I also see people complaining of moles in raised beds. And it’s not surprising. Moles love the stone-free soil and compost that has been enriched and encourages worms. It’s like putting a meal on the table for them. Some raised bed advocates suggest that its necessary to install wire mesh as the base of raised beds to prevent, moles, mice and rats from getting into the beds.
More Raised Bed Benefits?
Raised Beds Warm-Up Quicker in Spring. True. They do warm up a bit quicker. They also dry out a bit quicker when they overheat in hot weather. And if you want to warm up the soil in spring why not use a cloche, fleece or the many other available methods?
Raised Beds Mean Better Drainage. True, they can. If your soil is waterlogged or frequently floods than raised beds can help. So, in many cases, can good soil drainage. And well-installed soil drainage can last centuries .. much longer than most raised beds.
Raised Beds Mean Fewer Weeds. My question here is why? Do the weeds know that they are in a raised bed and shouldn’t be? OK, because it’s easier to reach the weeds it might be that gardeners weed a bit more and that reduces weed problems. But No-Dig is a much more efficient system if weed suppression is the aim.
Raised Beds Advance Sowing Dates. I’m unconvinced. Agreed the soil might warm up quicker but, as I suggested earlier, there are many ways to achieve this.
Raised Beds Are Great For Beginners. Really! Do beginners need all the expense of building beds, of filling them and of all the hassle that goes with them? Many beginners are working on a budget and to me, it makes better sense to put their limited budget into a few good tools, some seeds and maybe a few good books so they can learn the basics. Trying to convince them that raised beds are necessary seems to me to be doing them a great disservice.
Raised Beds Avoid Contaminated Soil. True, they might. If they are deep enough they might stop the roots of plants entering contaminated soil. But before building them we need to remember that many plants have roots that go a metre or more into the soil. Some will send their roots two metres or more into the soil. So our raised beds might need to be at head height for this to work. And, secondly, I’d like to know more about the type of contamination before investing in raised beds. Raised beds aren’t going to be the answer in all cases. And in many cases, the contaminated soil will be many metres below the present soil level. So the raised beds are a waste of time if solely for that purpose.
Raised Beds Prevent Weeds Coming In From The Paths. If you didn’t have weedy paths this wouldn’t be a problem. If paths are covered in a mulch of wood chip or similar, or if grass paths are mown regularly, there should be no weeds to contaminate the growing area.
Raised Beds Produce Higher Yields. Any soil/compost/bed that is well managed and not compacted produces higher yields than a badly managed, weedy, compacted plot. But raised beds aren’t needed to produce good growing conditions. Lots of other cultural methods are equally as good.
Raised Beds Decrease Erosion. I’ve heard this argument several times. The argument is that the raised bed contains the soils and so rain doesn’t wash the soil away. Advocates also claim that nutrients aren’t leached out of the soil. I don’t agree.
The soil in a standard garden doesn’t get flushed away when it rains. If it contains crops or green manures the soil is held together by the roots etc and a river of floodwater is needed to erode the normal garden. This argument confuses the erosion of poorly managed agricultural land with normal gardens.
As for the nutrients, why would they being in a raised bed make any difference whatsoever? Many nutrients are water-soluble so are a little easier to leach out if in a raised bed. And the insoluble nutrients aren’t going anywhere irrespective if in a raised bed or not.
Raised Beds Require Fewer Herbicides. The argument here is that if you have fewer weeds you don’t need to spray weeds as often. My question is how often do you spray weedkillers? And why are you using weedkillers when other methods of weed control are available? Raising the weeds above the soil surface doesn’t make much difference to the need to spray weedkillers or not.
Raised Bed Negatives
- Raised Beds are often expensive to build.
- The chemical used to treat the timber in raised beds is often phytotoxic, can cause skin rashes and sometimes contain heavy metals that are unsafe to work with. Rather than protect the plants from contaminated soil, the raised bed may introduce dangerous chemicals,
- Raised Beds dry out much quicker and need more watering than conventional beds.
- The need to introduce soil or compost from elsewhere is a sustainability issue. It consumes energy, produces CO2 and in some cases means products are transported globally for a single raised bed. For example, the Square Foot Gardening method suggests that raised beds should be filled with a mix containing perlite. Perlite is mined overseas, requires high-temperature furnaces to produce and is bulk transported thousands of miles. That isn’t green in any shape or form!
- The opposite of warming up faster in spring is that the raised beds cool down faster in the autumn.
- Pathways between beds need to be wider to accommodate wheelbarrows etc. So raised beds can be space inefficient.
- Raised Beds are more exposed to high winds and winter weather. That means some crops blow over in the wind.
- Plant roots near the edges of raised beds are confined and cann0t spread so far. They also get hotter and this can cause plant stress.
Raised Bed Conclusions
There is a place for raised beds in very specific situations but there are many negatives. These include cost, contamination and water issues, problems around sustainability and more.
Gardens Need Digging – More Gardening Myths?
More gardening myths?
Digging can be therapeutic, cathartic even. I’ve met so many people that don’t think they are gardening properly unless their muscles ache from digging. It’s one of those rites of passage they think they must undertake to join the fraternity of true gardeners.
But there is rarely a need to dig a garden. The exceptions are uncommon and don’t apply to most situations.
Let’s look at it logically. In nature, we have plants growing across vast tracts of the planet. And nowhere does nature find it necessary to dig the soil before plants can grow. And not digging doesn’t seem to inhibit plants one little bit. Consider the Amazon, the rain forests of Asia, the wealth of species growing in Southern Africa (the most diverse biome in the world). The plants don’t suffer from a lack of digging.
Indeed, in the Amazon, we have huge volumes of vegetation that has soaked up millions of tons of carbon. All without digging.
Large trees, no dig
And in North America, we have the largest trees in the world. The giant sequoia (Sequoiadendron giganteum) trees in California are enormous.
Also in the US is a Great Basin bristlecone pine, Pinus longaeva, that is over 4800 years old. I don’t believe anyone dug over the plot before it was planted!
Mankind first started digging when agriculture commended some 12,000 years ago. He probably used a pointed stick to loosen the soil and drop a seed in. Seeds would have grown if dropped on the soil surface as that is what happens in nature. But he discovered that germination rates were better if the seed was buried. Digging the soil in this way was a huge step in forward in mankind’s ability to feed itself. Later our species domesticated draught animals, invented the plough and mechanised the process.
But this isn’t an argument for digging or ploughing today. Today we can use farm machines to cut a slot in the soil and drop a seed in. And we can do it at rapid speeds. In the garden, we can grow seeds in modules and plant those into the sol. Or we can plant our seed into the soil surface without having first dug it. Whole gardening systems, such as No-Dig are based on this premise.
If the soil is compacted it is sometimes necessary to break the compaction or “pan”. This can be done with a soil buster or chisel plough. There is no need to invert the soil.
In other cases cultivations are used to bury vegetation or crop residues. Putting crop residues back into the soil is important but there are other ways to do it without ploughing.
Indeed ploughing and digging are destructive. They destroy the Wood Wide Web, the huge network of mycelium that is produced by soil fungi. The mycelium, along with the soil bacteria, break down insoluble rock and organic material and make it available to our plants. Without them the soil is impoverished and plants don’t thrive or have the same level of resilience to pests and diseases.
So, unless there are exceptional circumstances gardens don’t need digging. It’s hard work, unnecessary and destructive. A better way to garden is to go No-Dig. It’s far better than believing fairy stories about the benefits of digging.
Watch this space for more Gardening Myths. In the meantime why not check out my Gardening Dictionary and learn more about the words that confuse gardeners.
The “Cut The Leaves Off, It’ll Grow Better” Gardening Myths
The Potatoes Need Earthing Up – More Gardening Myths
Believing What Experts & Old Joe Say
The Trees Should Be Planted in Square Holes – More Gardening Myths
Garden Crop Rotation Myths
Gardens Need Digging – More Gardening Myths?
The Raised Bed Necessity Myth
Adding Sand to Clay Soil Makes It Free Draining – More Gardening Myths
Don’t Plant Anything Before The Last Frost – More Gardening Myths?
Plants Must Be Watered From The Bottom
The Candle & FlowerPot Heater Gardening Myth
#BiteSizedGardening Gardening Myths