DEALING WITH WEEDS

A large part of no dig’s success is to do with the relative absence of weeds. You save so much time, and are free to be more creative, with less of the constant need to weed.

Incidentally, I love wild areas and buzzing wildlife but am not a fan of weeds in the veg patch or flower borders. They can easily go from being just a few to swamping all other growth, especially new sowings and plantings. No dig makes it possible to enjoy a clean garden with mixed plantings, beautiful and productive, and full of wildlife too – especially in the soil.

  • Whenever soil has been dug, loosened or turned over, it recovers from the disruption by re-covering with weed growth – both from roots of perennial weeds and seeds of annuals.
  • When left uncultivated/undisturbed/undug, soil has less need to recover and grows fewer weeds, as shown by a look at Homeacres at any time of year. Check out the growing number of no dig gardens and allotments too.
  • No dig soil is full of beneficial organisms and microbes, which help plants to find nutrients and moisture, and convey health to the gardener, by feeding his/her gut biome, for example.

There are always a few new weeds, from seeds blowing in or brought in with composts, and they need removing by hand when small, or hoeing off as tiny seedlings. It is a ‘little and often’ approach.

Vegetable growing is bountiful and easier when weeding is just a small issue – still necessary but taking less time.

Every Saturday I have volunteers and students come along and work with me. When we were done for the day I asked them what they thought about the garden this spring season, and particularly what they think of the new no dig approach. They love it! The overwhelming response was that because they don’t have to spend so much time weeding, they have time to try fun and interesting new things.

Kylie Bisman, who had recently finished my online course, No Dig Gardening - May 2019
Kylie runs a rooftop market garden in Singapore

How to clear weeds

This depends on how many and which weeds you have, especially perennials, and how much organic matter you can source (see this link for a depth calculator of compost.)

The mulch(es) you lay are to clear soil of weeds through smothering/light-deprivation. Mulches of organic matter also feed soil and its inhabitants.

There is no need to dig before starting, or to incorporate manure and compost into the soil. Placing organic matter on top is the best way to bring soil alive because that is how soil organisms work, searching for and eating organic matter at the surface, then digesting and excreting in the soil, building a permanent structure in so doing. Incidentally, worms love working under black polythene, if you are using that initially.

In damp climates such as the UK, I recommend not using mulches of undecomposed organic matter, such as straw, which allow slugs to hide by day and eat your plants by night. Where slugs are potentially prevalent, compost is the mulch of choice because it does not harbour slugs. Composted beds look ‘bare’ when not growing vegetables, but the compost mulch is protecting soil below.

The time needed between mulching and sowing:

  • This can be instant if you have enough compost, say a 4–6 in/10–15 cm layer (see Option 2 below), and the timing is correct for sowing and planting.
  • Or it can be longer (as in Option 1 below), depending on the current perennial-weed situation, and above all whether the timing works for vegetables you want to grow, such as squash and potatoes.

Some weeds that need digging out initially

Docks, and woody plants such as brambles, are best removed with a sharp spade before mulching. Otherwise they push mulches up and reach light before they die. Use the spade to cut around bramble clumps, removing the main crown but leaving all small roots in the soil. For docks, remove the top 15 cm/6 in and then they do not regrow. I put these roots on my compost heap and they break down nicely.

Two options for clearing weeds

Option 1 – Using some organic matter and a polythene mulch

Step 1) Initial soil feeding and mulching of weedy plots

Firstly, apply any type of organic matter, for soil food and to increase the light deprivation of weeds below. Soil will be improving at the same time as weeds are dying off.

You can use partly decomposed animal manures or composts of any kind, and a small amount (say, no more than 25%) of leaves and grass clippings can also be good at this stage for feeding worms that get busy under dark mulches.

Any amount of organic matter is good on the weedy soil, from 3 to 10 cm, even 15 cm/1–6 in. There is no right or wrong amount to use, it is more a question of how much you have available, and how intensively you want to crop. Larger amounts of organic matter/compost result in more fertility, less watering and fewer weeds, and these results endure for a few years. However if you only have enough organic matter for a thin layer, that can still work.

Then apply a surface mulch of polythene on top of the organic matter (as opposed to with mulches of paper and cardboard, which are best laid on the ground with compost/decomposed organic matter added on top).

Polythene can be 600 guage or thicker plastic of any colour (the cheapest option), and you can also use woven polypropylene membrane (best not cut) or landscape fabric, which is cheap, light and easy to cut. However, fabric lets 30% light through so best lay cardboard first, then fabric on top.

This option is particularly worthwhile if you are clearing vigorous, perennial weeds in summer or autumn, to have ground clean for the following spring. Or if you want to grow, say, potatoes and/or winter squash.

See the photos below from Homeacres in 2016, showing a harvest of Crown Prince winter squash from ground that in April was 100% weeds, including some couch grass (Elymus repens), grass and bindweed.

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1. May 17th, after polythene had been put over weedy pasture five weeks earlier in April
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2. We spread six barrow loads of compost, about 3 in/8 cm deep – homemade compost and some old cow manure
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3. I cut holes in the polythene to plant five Crown Prince squash – this the harvest after four months, over 60 kg/132 lb
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4. In October, six months from the first mulching – the soil is clean except for bindweed

Step 2) Removing the polythene

Before removing, allow enough time for weed roots to be exhausted under whatever mulch has been used. The time taken for this depends on compost depth and the type/quantity of weeds. Annuals need two to three months; many perennials take six months in summer (or longer if some of the months include winter) for their roots to be exhausted from trying to grow in darkness.

If you peel back a mulch and still find white stems of weeds, this means that their roots are still alive, as in the last photo of the four above. At least in this case there was not a lot of bindweed, and we used a trowel to remove those shoots to further weaken the parent roots below. At Homeacres, on pasture full of perennial weeds, I remove polythene mulches after one growing season, say February to October at most.

Step 3) Easy growing

After the mulches have done their job, you will have a clean surface in which to sow and grow, which is the dark surface layer of compost you applied earlier. Seeds germinate and plants grow initially in the surface compost, then root into undisturbed soil below, which is firm but not compacted. Firm is good! Incidentally, in dry weather most soil becomes hard: this is normal and don’t worry, it softens with rain or watering.

Some perennial weed roots may still be sending up new leaves. In this case you need to keep removing the regrowth, as often as possible, to weaken the parent root even more. By year three, even bindweed is rare and easily manageable.

Option 2 - Using 10–15 cm/4–6 in compost

When you have enough compost to create beds with up to 15 cm/6 in on top of weeds, this is sufficient to prevent regrowth of weeds. An exception is if there are extreme amounts of bindweed (see this video), marestail or dense couch grass, in which case use Option 1 above.

15 cm/6 in compost, well trodden, or less with thick cardboard underneath, is enough to kill annual grasses and weeds, and to weaken if not kill perennial weeds such as buttercup, dandelion and smaller amounts of couch grass.

Subsequently, continue to use a trowel to remove any regrowth of perennial weeds, until parent roots die from lack of photosynthesised food from new leaves.

See this video, Two ways to clear weeds, where I demonstrate and explain these two methods.

The photos below show Homeacres in 2013, when I used a wheelbarrow to fill beds with compost to a depth of 15 cm/6 in. This was two-year-old cow and horse manure, homemade compost, and some green waste compost for the top inch or two. Any fine compost is good for the surface layer, your own if it has reached that stage, or old cow manure, mushroom compost or store-bought compost.

It was a large area that needed mulching and I only had enough cardboard for the paths and to go under the temporary sides. If I had been able to source it, cardboard laid over the bed weeds as well (before adding compost) would have slowed regrowth of buttercups, thistles etc. A few pushed through the compost and I needed to pull them in spring, until the parent roots expired.

The temporary wooden sides you see are fence posts laid on the ground, to hold the compost in place while it settled. Before the end of that first year I had removed most of them, as they were not needed any more and were giving habitat to slugs.

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Starting from weedy pasture in January and this is February – making beds with compost on top of weeds, and cardboard to mulch paths
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Four months later the garden is producing already; I planted (from the greenhouse) straight into the compost mulch
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April 2014 – most beds are now free of the temporary wooden sides
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May 2015

The importance of weed-free paths

Open-sided beds such as these are quicker and cheaper to create, and they offer less hiding places for pests. However you must have weed-free paths and with absolutely no grass, which otherwise invades beds with no sides.

As you can see in the photos above, I used cardboard on paths  to kill buttercups, dandelion and some couch grass. After 2–3 months the cardboard was decaying and weeds were pushing through again, weakened but alive.

They would regrow if not covered again so at this stage, it’s vital to lay more cardboard if weed growth is strong, or, say, wood chip, if weeds are few. I laid cardboard in early spring, late spring and mid-summer. By late summer all weeds were dead.

 

See my YouTube playlist , Dealing with Weeds, for more information.