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 Candle & FlowerPot Heater Myth

Tea Candles Produce 30-40 watts of heat. A fan heater produces 3000 watts. That’s a huge difference.

It’s the time of year for The Candle & FlowerPot Heater Myth.

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

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. 




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.  


Don’t Plant Anything Before The Last Frost

More gardening myths?

Beetroot are not overly frost sensitive
Beetroot is not overly frost-sensitive and will cope with all but the most severe frosts.

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.

Clay soils dry out and crack. More gardening myths?
Clay soils can be very wet or very dry. There seems little in between. More gardening myths?

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?

Square Foot Gardening sometimes Uses Raised Beds - More gardening myths?
Square Foot Gardening sometimes Uses Raised Beds, The problem is they recommend using unsustainable things such as Perlite to fill them.

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 Can Grow Intensive Crops - More gardening myths?
Raised Beds Can Grow Intensive Crops … But So Can Some Other Growing Systems

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

  1. Raised Beds are often expensive to build.
  2. 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,
  3. Raised Beds dry out much quicker and need more watering than conventional beds.
  4. 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!
  5. The opposite of warming up faster in spring is that the raised beds cool down faster in the autumn. 
  6. Pathways between beds need to be wider to accommodate wheelbarrows etc. So raised beds can be space inefficient. 
  7. Raised Beds are more exposed to high winds and winter weather. That means some crops blow over in the wind. 
  8. 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?

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.

Gardening Myths: Do Gardens Need Digging?

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.




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