As we’ve covered in the other parts of this series, weeds are super-plants that have found ways to dominate their environment and continue their presence in it over time. Thus, weeds develop roots systems that are hard to eradicate and from which new plants can spring up, they grow and set seed quickly, or they have mechanisms for spreading their seeds far and wide.
Removing weeds is therefore an important job for the gardener who wants to maintain the integrity of the intentional design of the garden and protect the plants that have been chosen to be part of that design. In this piece, we look at how we can best go about removing weeds and what we need to consider when working out the best approach for our garden.
As you can see, this article covers organic weed removal. I tend not to use chemicals in my gardens, so I don’t have much knowledge about the various weed killers available. But even if I did, there are so many evolving rules and regulations across the world about the use of herbicides and pesticides, that whatever I write now, based upon what is permitted where I live, is likely to go out of date quickly and not be applicable to you if you are not in the U.K.
So, what are the main principles to keep in mind when thinking about removing weeds organically?
Dealing with weeds organically is generally not a one-off act. In most cases, you need to take action several times or over an extended period to deal completely with a weed infestation. The good news is that this is a front loaded enterprise. Most of the hard work is done up front, whilst the follow up work is more in the nature of ongoing maintenance.
It’s worth remembering that even using chemicals to remove weeds does not produce instant results. In many cases, more than one application may be necessary, especially with tougher perennials.
The most important thing to remember when considering an organic approach to weed control is that weeds have the same requirements as any other plant. In particular, weeds need to photosynthesise in order to sustain themselves and, to do this, they need intact leaves and stems above the soil to receive the light from the sun.
We can therefore take advantage of this requirement in our weed control efforts, because even where a weed is able to re-grow from underground parts, such as root fragments, bulbs or corms, if we continually remove any leafy growth it puts on, we can weaken it to the point that it cannot survive.
The evolutionary urge of all plants, other than those that man has hybridised to sterility, is to set seed.
This is how the species survives. In fact many of the plants that we consider to be weeds have become weeds because they have become super efficient at flowering quickly and creating seeds that spread far and wide. As I point out in this post about how weeds thrive:
Sowthistle can produce between 20,000 and 25,000 seeds in its single year’s life-cycle. Chickweed, on the other hand, will produce only around 2,000 to 3,000 seeds per plant, but its life-cycle is only 7 weeks long, so the total number of seeds that it can produce in a year is enormous.How weeds thrive
So, as a matter of principle, we can reduce the threat from weeds if we take them out before they flower, or as a last resort, before they set their seed.
So, with the principles outlined above in mind, how do we actually get rid of weeds and how do we decide on the best way to do so?
The approach you need to take to get rid of your weeds is going to depend on the particular circumstances of the aeaa you are working with. I list a number of relevant factors below. As you read through these, think about the ones that may apply to you as that will help you choose the appropriate weed removal option.
See this post for details about the different characteristics of weeds.
In the following sections, I present a number of weed removal options and fill you in on the pros and cons of each one. These options are listed in the approximate order of how much time they take to work. So, if you can be patient, the techniques towards the end of the list might work best for you. If you need results fast, then look at the first few options.
Of course, how long it takes to achieve a weed-free space with any given option, will depend on how big the space is, how extensive the infestation and how hard you are willing or able to work.
Also, some options may simply not be practical in some situations and for some people. So, for example, if you have a bad back and a large space to weed, hand removal or double digging might not work for you. In that case, you’ll need to look at some of the longer term methods.
This method is all about digging your weeds out by hand. The best way to go about this depends to some extent on the type of weeds that are present and the size of the area that you have to weed.
You need to take care removing any weeds that have gone to seed because you will otherwise help the weed to disperse its seeds as you pull it out. The best way to prevent seed dispersal, is to place a plastic or paper bag over the seed head of the plant, gripping the neck of the bag tightly around the stem as you remove it. Sometimes it is easier simply to cut the stem of the plant with secateurs below the neck of the bag first and then remove the weed at its roots.
For smaller perennial or annual weeds you can use a hand fork to dig around the plant and lever it out at its roots. For larger weeds, especially perennials with extensive root systems, rhizomes, runners or stolons, you will need to use a garden or border fork.
In essence the technique for using a garden fork is the same as that for using a hand fork. You need to work the prongs of the fork around the plant so as to loosen it at the roots. With a garden fork, you use your foot to drive the prongs into the soil surrounding the plant and then your arms and upper body strength to loosen the plant and lever it out.
The essential thing to remember when hand removing weeds is that you need to dig out every last scrap of root, rhizome, stolon etc. if you are are to truly achieve a weed free outcome. Often it is simply not possible to do this because some piece will remain hidden in the soil. But if you do the best you can, then whilst there may be some re-growth it should be limited – and something you can deal with when it emerges.
Hoeing involves cutting off weeds just below the surface of the soil. A dutch hoe, like the one pictured below has a cutting edge at the front. You run this edge through the soil towards the weed and it cuts the stem of the weed under the surface. This is the exact hoe that I use, by the way. I got mine from Harrod Horticulture (affiliate link) with a rake to match.
Hoeing is best for annual weeds or perennial weeds that don’t have root systems that allow the plant to regenerate (e.g. rhizomes, tubers or tap roots). That said, if you hoe perennial weed each time they regrow, you will weaken and kill most of them over time.
Hoeing is also a good method when you have weeds growing amongst valued plants. It is a bit more risky than hand removal, because you have to be careful not to accidentally shove the hoe into the stems of the plants you want to keep. But it is a bit easier on the body using a hoe than to be down on hands and knees weeding. Perhaps if I say that as I have got older, hoeing is my preferred approach, you’ll understand what I mean.
Finally, hoeing is fine for smaller areas, but if you have large areas infested with weeds, trying to clear the area by hoeing will be a long slow process, especially as you are likely to have lots of tenacious perennial weeds is such a space.
Weeds can be burned off using a flame gun, as pictured. This would typically be fuelled by butane gas, but some electric powered versions are available.
This is another method best suited to small spaces and ‘spot-weeding’ – i.e. picking out particular weeds, rather than dealing with large weedy areas. It is often used effectively for weeds on hard surfaces or those lodged in the cracks between paving slabs.
Similar to hoeing, burning off weeds only affects the above-ground parts of the plants. It is therefore effective on young and/or annual weeds, but won’t immediately eradicate well rooted perennials. As with hoeing, burning can weaken such weeds over time, so removing them in this way is a longer term operation.
When burning off weeds, you only need to keep the flame on the weed for 2-3 seconds. As you do this, the leaf surface should change to a dull, rather than shiny appearance. This should tell you that the weed has been killed. Similarly, if you press the leaf between your fingers and leave an imprint on the leaf surface, you can be sure that the burning has worked.
There are some safety considerations with weed burning. Firstly, don’t burn if conditions are very dry and there is any risk of starting a grass fire that could spread out of control. Second, don’t burn around any loose dry material (e.g. sticks, bark etc) that could act as tinder. Thirdly, check that weed burning is permitted in your area. In some places it is banned.
This is an interesting one. You will often see vinegar hailed as an effective organic means of killing weeds. But, to be clear from the start: This is a method I do not recommend.
The idea here is that a vinegar solution will act as a ‘natural’ weedkiller – and in fact there is some evidence that vinegar will kill leaves and thus be effective on young annual weeds. However, as gardener and chemist Robert Pavlis shows us with this experiment, vinegar at sensible domestic concentrations (5-7%), has little lasting effect.
Vinegar can be more effective at higher concentrations, but at that point it is not really vinegar any more. Instead, it is the dangerous chemical – acetic acid which, at 11% concentration can burn skin and cause eye damage, and at 20% concentration and above will corrode some metals and potentially cause blindness.
So, if acetic acid is used, it should only be applied while using protective clothing, gloves and goggles. But even at the higher concentrations, it is only effective on some weeds. What is more, it will kill the bugs and micro-organisms that are essentially for healthy soil, and will also be harmful to the larger animals and insects.
Therefore, in short, my advice is keep the vinegar in the kitchen where it belongs.
The double dig method of removing weeds involves burying the weeds at at depth and in a way that means they won’t regrow. This method works best for annual weeds or shallow-rooted perennials.
The advantage of this method is that it is cheap and straightforward and allows organic matter and manures to be incorporated at the time the work is carried out. This disadvantage is that it is hard work and therefore difficult to do over large areas.
Here is how it works:
This is a method borrowed from agriculture, but it can work well in domestic situations, as long as you have patience and time to spare.
As the name suggests, this method starts with the preparation of a seedbed. This means you’ll need to hand weed, hoe or maybe double dig first to clear out the perennial weeds and annuals that are already growing in the bed. Then you need to rake the over the soil, leaving a fine tilth as if you are going to sow seeds.
The next step is to do nothing.
The cultivation you have done so far, will have brought a huge amount of weed seeds to the surface. If you leave the bed for two or three weeks, these seeds will germinate. Wait until they are big enough and then hoe them all off.
You’ll now have a bed relatively free of weed seeds, which means there will be much less competition for whatever you intend to grow. This method is is especially good if you intend to sow seeds that are slow to germinate or will be broadcasting seeds, which means hoeing is not possible.
Chicken can be an effective method of weed removal, although they won’t get rid of the toughest perennial weeds.
Given the opportunity, chickens will root around in soil, eating any plants they can pull out or loosen. This means that, left to their own devises, they’ll eat your prized plants, as well as your weeds. So, they need to be contained temporarily in the area they are working. This can be done with temporary fencing of some kind or with some kind of moveable structure that enables them to cover a section of ground at a time and then be moved on. In permaculture circles, this is called chicken tractoring. Here is how to make one:
Apart form weed clearing, chicken will eat pests like slugs, and will also provide you with a nice sprinkling of organic fertiliser with their poo. However, you need to make sure you don’t leave them in one place for too long or the soil will become a bit too acidic from the concentrated droppings.
This method involves using a mechanical rotovator, to break up a heavily weed infested area and ready the ground for planting.
In my view, this method should only be used when you have no, or very few perennial weeds. As you will see in this post, most perennial weeds will not only regrow, but multiply, if you break up the underground parts of the plants. For example, bindweed, has roots which extend over significant distances under the surface. When these are cut or damaged new plants will emerge.
Rotovating can work as the initial stage of working a heavily infested or compacted site, but it won’t be an end in itself. You’ll need to combine it with one of the other methods, such as hoeing or hand-weeding You’ll also need to weigh up whether the potential increased proliferation of perennial weeds is outweighed by the advantages of breaking up the site.
This is in fact one of the most effect methods for removing weeds. It can also taking a while. Hence it appears at the bottom of the list.
This method relies of the principle of preventing photosynthesis. By removing one of the essential requirements for growth – sunlight – you condemn the weeds to an early death.
All that is involved here is laying some kind of covering over the weeds that will prevent light getting through. There are a variety of options:
My preferred method is to lay down organic mulch and then cover with weed suppressing sheeting. The advantage of this approach is that the organic matter encourages worms and other bugs to lend you a hand in improving the soil structure while the weeds are dying. The sheeting is also permeable, so the soil can stay damp which is what the worms need.
This, however, can be a lengthy process. Of course it depends on what kinds of weeds are present and in what numbers. But in warmer weather, there should be considerable progress in a couple of months. In colder areas or times of the year it will take longer.
Even if every single weed has not been killed completely when you remove the covering, you will find that they are weakened considerably and much easier to remove by hand.
As you can see there are lots of ways you can remove weeds organically and the reality is you’ll probably need to rely upon a combination of the various options.
It is useful to remember the principles about preventing flowering and photosynthesis. But it is probably most important of all to just keep at it.
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