The Weed Problem: Understanding Weed Dispersal & Prevention
Understanding Weed Dispersal: Weeds, Those Plants In The Wrong Place, Can Be The Bane Of The Gardener’s Life. Where Do The Come From & How To Stop Them?
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The secret to preventing many weeds is easier if we focus on Understanding Weed Dispersal. Knowing how they got into the garden is key to preventing weed dispersal and gaining a foothold in the garden.
Common field speedwell, Birdeye speedwell, Veronica persica, an ephemeral weed of many gardens
We need to get on top of weeds as they create a lot of work, complete with our crops, are sometimes potentially harmful to pets and livestock, plus some are unsightly and reduce the overall aesthetic value of our gardens.
Of course on the plus side, and weeds have a plus side, weeds tell us a lot about what is happening in the soil, what it’s nutrient status is and even hint at the moisture levels and pH. And I have to confess that I find many “weeds” top be beautiful and encourage them in parts of my garden. But I suppose once I do that they become wanted plants and can’t be classified as weeds.
Understanding Weed Dispersal …. Where Do Weeds Come From?
Weeds can be introduced to a garden in several ways:
Wind-borne Seeds: Many weeds have tiny, lightweight seeds that can be easily carried by the wind. These seeds can travel long distances, landing in gardens and taking root. Common wind-borne weeds include dandelion, thistle, and poppy.
Carried on Boots, Equipment, and Clothing: Weeds can hitch a ride on your boots, gardening tools, or even your clothing. Seeds can stick to your shoes and be brought into your garden from other areas. Similarly, gardening tools can carry seeds from one garden to another.
Purchased Plants: Sometimes, weeds can be introduced to your garden through purchased plants. These plants may have weed seeds attached to their roots or in the soil around them. It’s important to inspect plants carefully before bringing them home.
Soil Contamination: If you bring in new soil for your garden, it may contain weed seeds. This is especially true if the soil is from a contaminated area.
Self-Seeding Weeds: Some weeds are self-seeding, meaning they produce seeds that can easily germinate and grow into new plants. Examples of self-seeding “weeds” include poppy, calendula, and nasturtiums. I’m not sure I like this term as most weeds seed or regenerate on their own. Perhaps I should classify them as fast growing weeds. Or weeds that produce lots of seeds. Or even weeds with a high germination rate …. Do you see where I’m going with this?
Animal Fur Dispersal: Animals can also play a role in spreading weed seeds. Seeds can stick to animal fur and be carried to new locations. This is particularly true for burdock, which has spiny seed heads that can easily attach to animals.
How Do We Encourage Weeds?
This might seem a strange heading as surely no one encourages weeds .. except me, when I allow them to grow because I think them beautiful … or tasty. The answer is we often inadvertently encourage weeds by our actions. Let me explain more about Understanding Weed Dispersal.
The soil contains huge volumes of weed seeds. Weeds have been spreading seeds for thousands of years and some of them survive decades before germinating. A prime example is the common poppy. A field near my market garden was sold and turned from grassland to arable. It was the first time it had been ploughed in over 50 years. So had not grown poppies in that time. However, within weeds of ploughing the poppies were growing like mustard and cress. And in just a few more weeks the filed was a s red as Flanders Field.
The whole landscape was blood red with poppies. It was a beautiful sight in one sense, but a stark reminder of how seeds can survive very long times.
And if you think 50 years is a long time then consider the date palm tree that came back from extinction. This is the story of a date palm seed that was planted, grew and fruited after 2000 years. See the video below!
But that isn’t the only way we encourage some weeds.
Cultivation Methods Means Understanding Weed Dispersal Issues
I’m not a great fan of rotations in gardens, I find them totally unnecessary in 99% of cases. But in agriculture and larger scale crops growing there are occasions where we need to ring the changes. It’s not that we can’t grow the same crop on the same land year after year, we usually can without huge inputs or loss of yield. The problem is that if we regualrly do the same thing we can give weeds the opportunity to exploit any chinks in our armour. Let me give you an example.
In the 1980s a lot of lettuce growers used a weedkiller to keep weeds down. They would cultivate, plant block raised lettuce and spray with a product called Kerb50. This was “pre-emergent) herbicide that stopped weeds from germinating. For years this worked very well and many growers become reliant on it. Personally I had my doubts about using herbicides but more on that in a moment.
However, the chink in the lettuce growers armour was finally exposed. It was a little known weed that was immune to the herbicide. This meant that both the lettuce and the weed thrived with no other competition.
The weed was called Galinsoga parviflora aka Kew Weed. But the growers called it Gallant Soldier … because it would never fall down and die.
Not only did it survive but it grew very fast and shed its seed before the lettuce were harvested. That meant there was always seed in the ground ready to be “selected” or by the herbicide. At certain times of the year it grew so fast it swamped the lettuce crop.
Using herbicide encouraged Gallant Soldier.
Getting rid of Gallant Soldier was easy, stop spraying. I didn’t suffer from Gallant Soldier as I hoed my lettuce in preference to sprays. That meant all weeds were killed by the tractor mounted hoe I used. And the hoe gave a benefit. It let air into the ground and encouraged faster growth because of it.
Any repetitive cultivation method that gives the weed a very minor advantage will encourage it. And as two weeds become ten and ten become hundreds the problem weeds can swamp us.
Drainage, pH & Other Weed Encouraging Factors
If we allow our allotments , gardens or fields to sit wet, without drainage, then weeds tha prefer damp ground will proliferate. Drain the land and the weeds are soon reduced.
Ditto pH. Many weeds have a preferred pH range. Some love chalky soils, some prefer acid soils. Change the pH and the weeds respond to the change.
Experienced growers can quickly tell you if your soil needs liming to draining by looking over the hedge. They only need to see which weeds are proliferating. For example, on my morning walk today I walked along a footpath next to a grass field. It had a lot of buttercups and thistles growing in it. The thistle was the marsh thistle .. the clues in the name. And buttercups prefer damp acid soils. The two plants incline me towards saying the field is damp and acid.
Buying Weeds
A huge source of weed seeds and seedlings involves them being transported in pots. Look at the weeds in the pots when you buy plants for seedlings. Otherwise you could get more than you bargained for. Understanding Weed Dispersal prevents this problem.
Why Are Weeds Problematic?
Weeds can be problematic for several reasons:
Competition with Desirable Plants: Weeds compete with desirable plants for resources such as sunlight, water, and nutrients. This can reduce the growth and health of our garden plants.
Damage to Crops and Livestock: Some weeds can be harmful to crops and livestock. For example, certain weeds can produce toxins that can make animals sick.
Reduced Aesthetic Value: Weeds can create an unsightly appearance in a garden or lawn. This can reduce the overall aesthetic value of a property. Weeds such as Japanese Knotweed may even prevent a house sale. It will certainly stop us getting planning permission until it is eradicated.
Increased Maintenance Costs: Weeds can require additional time and effort to control. This can increase the cost of maintaining a garden or lawn.
Preventing Weed Invasion
To prevent weeds from invading your garden, consider the following:
Regular Weeding: Removing weeds before they can set seed will help to control their spread.
Mulching: Mulching can help to suppress weed growth by blocking sunlight.
Choosing the Right Plants: Select plants that are known to be resistant to weeds.
Inspecting Purchased Plants: Carefully inspect plants before bringing them home.
Cleaning Tools and Equipment: Clean your gardening tools and equipment after each use to prevent the spread of weed seeds.
Avoiding Contaminated Soil: Avoid using contaminated soil in your garden. For example I know Gallant Soldier was spread around market gardens near me on contractors equipment and tractor tyres.
By following these tips, you can help to prevent weeds from invading your garden and reduce the amount of time and effort you need to spend on weed control.
