Weeds in a polytunnel are not something that we can eliminate entirely. Nor should we really wish to do so. However, there are ways to make weeding less of a chore.
Many new gardeners make the mistake of thinking that they are in a fight against weeds in their gardens, and need to wage war against this ‘problem’.
But weeds are not a massive problem and working out how to get rid of weeds in a polytunnel means recognising where they can actually be useful rather than something we need to remove.
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Why Weeds are Often Useful and Not a Massive Problem
Weeds, it is important to remember, can be useful to us in a range of different ways. Some have uses within our homes while others have uses in the garden, either while they are still in active growth or when they are reduced to organic matter.
First of all, it is important to recognise that weeds are frequently just plants that are particularly well suited to growing in a particular environment. Often, when these are native to a region, they are a vital part of the natural ecology of the areas in which we live.
While non-native, invasive plants must of course be removed as soon as possible for the good of the system, native wild plants can often be beneficial plants to retain – at least in some parts of a polytunnel garden.
Some weeds are edible and are great to add in your recipes for spring foraging, or have other uses – providing plant fibre, for example, or having medicinal properties. Some are wonderful wildlife attractants or for other reasons make great companion plants. We’ll explore this in more detail below.
Why Weeds Sometimes Need to Be Removed in a Polytunnel
Of course, just because weeds can be beneficial that does not mean that we want to simply leave them to grow in every situation.
Sometimes, knowing how to get rid of weeds from a particular part of a polytunnel garden can be beneficial, even when they are of a type that can be useful elsewhere. The term ‘weed’ really is one that is all about context.
Some weeds, of course, will always be problematic – non-native invasive plants like Japanese knotweed belong in this category, but it is still important to know how to stop Japanese knotwood from spreading too. But here we are talking about native weeds which can often be beneficial, and when even these may sometimes need to be removed.
One reason that you should know how to get rid of weeds from your polytunnel is because of competition. If weeds grow up in your growing areas they can often compete excessively with the crops and other plants that you are cultivating there. Excessive competition can reduce the strength, vigour and productivity of your garden and reduce the yields that you are able to achieve.
In a restricted space such as a polytunnel garden, you need to know how to get rid of weeds from here too, even if they are not overly competitive with their neighbours, because every inch of space is at a premium. You may simply decide that other plants will be more useful additions to the space.
If You Can Keep the Weeds in Question:
If the weeds are not adversely affecting their companions through excessive competition, and they are not taking up space wanted or required for other plants, then we can definitely consider keeping them.
This may seem almost shocking for more ‘traditional’ gardeners who have been ‘trained’ to rip out any plant that ‘does not belong’ as soon as they emerge. But when we simply accept that plants commonly called weeds are plants that can have their places, we can:
Consider Weeds as Additional Crops
As mentioned above, some weeds can have edible or other useful yields. They can therefore be considered not merely as competition to the main crops that you grow but also as additional crops in their own right.
A number of the common weeds found in UK polytunnel gardens could be treated as additional crops – all the better for the fact that they crop up on their own without us having to lift a finger to sow or plant them deliberately.
Stinging nettles, dandelions, fat hen, chickweed… and more… can all be useful plants – producing food and many other resources. Why shouldn’t we, therefore, give these useful species and other useful species some space in and around our polytunnel gardens?
Keeping small patches or areas of weeds in a polytunnel and harvesting from those areas to keep them in check, we can gain the yields that those weeds can provide without sacrificing too much area within a polytunnel to these species.
Keep Weeds in Place as Companion Plants
Weeds might also be retained between and around other crops as long as they do not compete excessively with the other crops. These weeds can not only potentially provide their own yields but can also be excellent companion plants – aiding the key crop species in a number of different ways.
For one thing, weeds can provide environmental enhancement. They may provide some beneficial shade for neighbours keeping them a little cooler and preventing bolting during hot weather.
Weeds can also, especially while they are in flower, attract a range of insects. This can help with both pollination and pest control. Weeds may serve as attractants, or deterrents. They can also sometimes serve as trap crops.
Retain Weeds as Ground-cover Plants or Cover Crops
‘Weeds’ may also help to retain soil moisture and protect the precious soil ecosystem as a kind of living mulch.
They can be good ground cover between certain other plants and may also sometimes serve as cover crops or green manures between the times when main crops in a growing area are in the ground.
It can be beneficial for the soil to keep a living root in the soil over as much of the year as possible. And some weeds can serve more specific functions to enhance the soil and improve soil health. For example, some, with deep taproots, can help to aerate the soil and reduce compaction.
If the Weeds Have Got to Go:
Even if, due to competition or lack of space weeds do have to go, that does not mean that they cannot still be of use.
The weeds that you need to remove from your growing areas should be viewed as a valuable resource that can be used to perpetuate the cycles in your polytunnel garden and keep your soil and your plants healthy over time.
Chop and Drop Annual Weeds
Often, annual weeds that pop up in productive growing areas can simply be chopped and dropped onto the surface of the soil to return their nutrients to the system.
In some cases, you may use a hoe to quickly and easily uproot these smaller annual weeds – though care is obviously required around shallower rooted crops so that you do not do any damage to these along with the weeds.
In many instances, you can simply know how to get rid of weeds by lifting them out by hand, pulling them up from the soil before simply dropping them back down upon it where they were originally growing.
Add Weeds To Your Composting System
Sometimes, of course, weeds are not of a type that we can simply leave on the soil surface around our crops and it is important to follow natural ways on how to get rid of weeds.
In some instances when learning how to get rid of weeds from your polytunnel, it may be better to remove the weeds from the growing area entirely. If this is the case, we should still remember that weeds are a valuable resource, containing nutrients that we should take steps to return to our gardens.
One of the most effective ways on how to get rid of weeds safely be added to a composting system. Though whether or not you should add specific weeds to your composting heap or bin will often depend on a range of factors including their ability to spread, and their stage of growth.
Weeds that easily proliferate from root sections, or those that have gone to seed, may not be the best choices to add to many composting systems.
However, you should note that with some hot composting systems, weed seeds and root sections would be killed off by the heat, so adding them to this type of system should be just fine. Always consider the weed and the type of composting system carefully before deciding where to send the weeds you remove from your growing areas.
If weeds cannot be composted safely in your main composting system, note that you may still be able to allow them to compost down in a hole dug in a corner of your garden, buried beneath the soil.
Make a Weed Feed for Your Plants
Weeds from a polytunnel might also be used to make an organic, liquid plant feed. Weeds can be added to a lidded bucket of water in order to rot down and make a stinky brew that will be full of plant nutrients and which will help other crops grow strong.
You can make a relatively high in nitrogen general weed feed, or aim for specific nutrient mixes by using specific weeds that might be considered to be ‘dynamic accumulator’ plants. Experimenting with liquid plant feeds in your garden can help you find solutions that work in your garden.
How to Get Rid of Weeds
Now you should be aware of the different ways on how to get rid of weeds from your polytunnel, each with their own strategies and benefits. To further protect your domestic polytunnels from weeds, you should introduce ground cover weed controls to your gardening practices and thus further prevent weeds from reappearing once you have removed them.
For more tips on weeds in your garden, we have an effective guide on the types of weeds you will likely expect to see in the UK.
What causes weeds to grow in a polytunnel?
Weeds in a polytunnel can be introduced through wind, water, soil, or contaminated tools and equipment. Weed seeds can also be present in compost or brought in by animals.
Are all weeds harmful to plants in a polytunnel?
While most weeds compete with cultivated plants for resources, not all weeds are equally harmful. Some weeds may have beneficial properties or can be tolerated if they do not pose a significant threat.
How can I prevent weed growth in a polytunnel?
Preventive measures include clearing and cleaning the area before constructing the polytunnel, using weed barriers like landscape fabric or mulch, and maintaining proper ventilation to reduce humidity.
What are the best manual methods to control weeds in a polytunnel?
Effective manual methods include hand-pulling weeds, hoeing and cultivating the soil to disrupt weed growth, mulching around cultivated plants, and practicing solarization during empty periods.
Waddington, E., (2022) This is How I Make Weeding Less of a Chore. Treehugger. [online] Available at: https://www.treehugger.com/make-weeding-less-chore-5324615 [accessed 04/09/23]
Gov.UK. (n.d.) How to Stop Japanese Knotweed from Spreading. [online] Available at: https://www.gov.uk/guidance/prevent-japanese-knotweed-from-spreading [accessed 04/09/23]
Elizabeth Waddington is a writer and green living consultant living in Scotland. Permaculture and sustainability are at the heart of everything she does, from designing gardens and farms around the world, to inspiring and facilitating positive change for small companies and individuals.
She also works on her own property, where she grows fruit and vegetables, keeps chickens and is working on the eco-renovation of an old stone barn.
To get in touch, visit https://ewspconsultancy.com.