Fewer weeds in no dig

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 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, full of wildlife too – especially in the soil.

  • When soil is 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/no dig, soil has less need to recover and therefore grows less 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, for example by feeding his/her gut biome.

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. Mulching to clear soil of weeds in polytunnels is the same story, see my early posts of 2013 for how I mulched a tunnel of weeds, starting here and scroll down halfway. See Ferryman Polytunnels for some ideas of structures and prices, and my article on this site. See this page in Italian, here.

Feedback May 2019 from Kylie Bisman, who runs a rooftop market garden in Singapore:

Every Saturday I have volunteers and students come along and work with me up there. When we were done for the day I asked them what they think about 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 we don’t have to spend so much time weeding we have time to try fun and interesting new things.

(Kylie had recently finished my online course about no dig gardening).

How does someone start if they have no experience?

Start small, even one bed of 1.2×2.4m can grow a lot of food. Cropping a small area well is more productive than having weeds and empty spaces on a larger area, and you will enjoy it more. Enjoyment is important and no dig is fun. I receive many comments like this:

“We’re just now entering year 2 of no dig and it certainly is very enjoyable compared to past years of endless weeding and bed preparation.”

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Soil condition, firm is good!

Soil compaction is thankfully rare. In fact compaction is far more common in cultivated soils, where tools have broken the existing structure. Mini layers of compaction then result in some alcohol being produced which attracts slugs, see the work of Professor Elaine Ingham. My no dig gardens suffer very little slug damage.

Often soil feels firm or even hard, especially when dry, and this is fine for plants to grow in. Within the firmness is a tight structure of fine air channels and root passageways, as well as good drainage capacity. Even in clay, and I write this from experience, you need to trust! Plants root better in dense, firm soil than in one whose structure is loose and offers less support to the plants above, and loses more moisture to evaporation. No dig works well on clay soil, see below:

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1 Homeacres when I arrive in winter 2012-13, three five tonne loads of well rotted cow manure are ready for mulching
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2 March: bed preparation varied as I tried different methods, mostly it was 6in/15cm well decomposed organic matter on the weeds
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3 May, growth has started well in the compost. Wooden sides are mostly temporary, paths mulched with cardboard
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4 June 2013, many harvests already, and plants are now rooting into the soil below, as weeds are mostly dead, some perennials still need a trowel

Clearing weeds

The first step 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 clean soil of weeds by a smothering, light-deprivation effect. Mulches of organic matter also feed soil and its inhabitants. There is no need to dig before starting, or to incorporate manure at depth. 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 can be instant if you have enough compost, say a 6in (15cm) layer (option 2 below), otherwise within 6-12 months as in option 1, depending on the current perennial-weed situation, and whether the timing works for vegetables 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 a sharp spade to cut around bramble clumps, removing the main crown but leaving all small roots in the soil. For docks, remove the top 6in (15cm) and then they do not regrow; I put these roots on my compost heap and they break down nicely.

For marestail/equisetum, the procedure is the same as for couch grass, bindweed, ground elder etc – no need to dig first, just mulch. A lady from Manchester on a Homeacres course in 2019 told us how well this is working, after she mulched a marestail infested allotment the previous spring, as a complete beginner. Now she notices a much-reduced vigour of the weed, which also is easy to keep pulling, diminishing its regrowth each time.

Allotment holders comparing dig & no dig say the no dig is so much more effective for marestail control and eventual eradication.
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5 Same view June 2014, paths mulched with any organic matter including wood shavings. All perennial weeds now dead except for bindweed in some places. First plantings here for summer harvests mostly
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6 Same view Sept. 2017. noe the oly wooden-sided beds are the two of my dig/no dig experiment, most veg here are second crops planted in the summer after a harvest, with no new compost added

Wooden sides?

It’s often assumed that growing in beds means you need permanent sides, but this is untrue, though they are sometimes useful, for example in the first 6-12 months of option 2. Temporary sides (such as old fence posts) help to keep compost-filled beds in shape, for the first few months, as in the first photo of option 2 below, February 2013, I then lifted off the unfixed wooden sides in early autumn of that year, once the beds’ compost had settled and path weeds were dead – this had needed a further laying of cardboard in May, and again in July for a few places with couch grass. It’s quicker and cheaper to create open-sided beds, and they offer less hiding places for slugs and woodlice. However, you must have weed-free paths for this to work and absolutely no grass, which otherwise invades beds with no sides. This is why I used cardboard on paths in the first few months at Homeacres, to kill buttercups, dandelion and some couch grass. After six months or so, once those weeds had died from lack of light and the cardboard had mostly decomposed in situ, I spread some organic matter as surface mulch: half-rotted leaves, old straw, green waste compost and decomposing woody material are suitable. Then I treat paths like the beds, they receive a little compost from birds kicking it off the beds (looking for worms), and I weed where necessary, to keep them immaculate.

OPTION 1

Some organic matter and polythene mulches

See the video for more on this When significant perennial weed roots are present and you are using say 1-2in (3-5cm) compost, there are still possibilities for growing veg in the first summer. Occasionally, slugs may make this tricky.

1) Initial soil feeding and mulching of weedy plots

Any organic matter can be applied on top, for soil food and to increase the light deprivation of weeds below. Animal manures partly decomposed, composts of any kind, a small amount say no more than 25% of leaves and grass clippings, are all good at this stage for feeding worms which get busy under dark mulches. Soil is improving at the same time as weeds are dying off. The surface mulch of polythene, cardboard or paper is applied on top of the organic matter.

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Experimenting with different surface mulches on soil with couch grass, buttercups and cow parsley.

Polythene can be 600 guage or thicker plastic of any colour (cheapest option), 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, taking a harvest of Crown Prince winter squash from ground that in April was 100% weeds including some couch grass (Elymus repens), grass and some bindweed too.

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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 3in deep: homemade compost & some old cow manure
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3 I cut holes in the polythene to plant 5 Crown Prince, here is the harvest after four months, over 60kg
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4 In October, 6 months from the first mulching, the soil is clean except for bindweed

2) Next step depends on compost depth and weeds

Before removing polythene or membrane, allow enough time for weed roots to be exhausted under whatever mulch has been used. Annuals need two to three months, many perennials take from six months or sometimes longer, for their roots to be exhausted by trying to grow in darkness. If you peel back a mulch and still find white stems of weeds, 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.

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Carpet applied to weedy pasture three months earlier, with 1in (3cm) old horse manure. Bindweed Convolvulus arvensis is still growing white stems and leaves. White because they cannot photosynthesise, therefore the parent root is weakening all the time.

3) Normal Growing

After polythene/cardboard/membranes have done their job, you have a clean surface to sow and grow, which is the dark surface layer of compost you applied earlier, or apply afterwards. 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 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, as happened with the bindweed after my carpet mulch. 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 4-6in (10-15cm) compost to create beds

When you have enough compost to create beds with up to six inches (15cm) on top of weeds, this is sufficient to prevent re-growth of weeds. An exception is if there are extreme amounts of bindweed, (see video), marestail and dense couch grass – in which case, use option 1 above. 6in/15cm 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. Use a trowel to remove any regrowth of perennial weeds, until parent roots die from lack of photosynthesis-food from new leaves.

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Starting from weedy pasture in January, this view 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
  • Cardboard for paths only, temporary wooden sides: In the photos of Homeacres 2013, I used a wheelbarrow to fill beds with 6in/15cm depth of compost. 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.
  • For the large area to mulch in 2013, I had only 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 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 wooden “sides” you see above are fence posts laid on the ground, to hold compost in place while it settles. Before the end of that first year, I had removed most of them, as they are not needed any more and were giving habitat to slugs.
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April 2014, most beds now free of the temporary wooden sides
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May 2015
  • In the image of a new bed below, half the bed had cardboard under the compost, half did not and in this case it made little difference to weed regrowth, because the perennial weeds were not too vigorous, having been regularly mown for three years previously. If there are vigorous perennial weeds, a cardboard layer is worthwhile – thick cardboard is best, or two layers of thin cardboard. We filled this bed with half animal manure (old) and half my own compost, no green waste.
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Filling a new bed on grass, one half with cardboard: the six inches of organic matter in this bed was enough to kill grass, dandelions and buttercups

For an approach like this and to grow potatoes at the same time, see Naomi Schillinger’s blog of summer 2012. Vegetables are hungry plants and require a soil that is well structured and full of life. First year dressings of organic matter may seem a lot but will repay the effort for years to come. Until the advent of chemical fertilisers, larger amounts of compost and manure were always used for vegetable growing. Since 1945 especially, more emphasis has been placed on chemical nutrients from synthetic or concentrated sources, but these fertilisers cannot provide soils with food for all its myriad of inhabitants who are so necessary in growing healthy plants. And some of their nutrients leach away in rainfall, which is both a waste and a pollution.

No dig clay soil no problem

At Lower Farm my soil was clay, and I found that all vegetables rooted into it. In France I gardened on dense white clay, with lovely harvests. Clay soil is great for no dig: worms and other soil life improve its structure, you save so much time, and there is good nutrient + moisture retention.

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These parsnips were sown in well decomposed manure on top of heavy clay soil

To clarify, my clay soil at Lower Farm was in 2010 growing vegetables as in the middle picture and parsnips as in the right hand photo of the gallery below. No dig, no loosening or forking, just soil organisms doing the work and they are fed with a compost mulch. Parsnip and other seeds are sown into this compost.

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This clay soil at Lower Farm had been compacted by machinery in 1998/9. Then I surface mulched only, with compost, and soil life gradually recreated an aerated structure. This is September 2010.
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View of vegetables growing in this same clay soil, no dig for 11 years, September 2010
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Grown in this clay soil, March 2011 I needed a spade to lever out these parsnips, sown a year earlier in the compost mulch, then they descend without forking into the soil below.

At Homeacres my soil is dense silt and everything roots into that too. In my first garden 35 years ago, soil was Cotswold brash, very stony, and no dig was successful there as well. Undisturbed soil develops and maintains a honeycomb structure of small air passages, especially when it is fed annually with an inch or so of compost on top. This compost can be animal manure that has been stacked for six months or more, your own compost, municipal or mushroom compost, leaf mould etc

  • Wood chips: A variation is to apply 6-12in (15-30cm) of wood chips, and/or bark and/or shavings, to kill off weeds. If you have access to these materials for free, its worth considering. But the downside is a wait of up to two years before the lower layers have turned to compost, by which time you can plant (easier than sow) into that lower layer, with the surface wood continuing as weed-suppressing mulch and eventual soil food. Lots of wood mulch encourages woodlice and they nibble leaves such as spinach and cucumber.

No dig ongoing

The surface layer

Sowing small seeds into large lumps of compost and manure is unlikely to succeed, so keep the most crumbly and finest organic matter for your surface layer of mulch. Likewise, an excellent time to spread compost is in autumn, as soon as the previous crops finish. Then there is time for frost to break up any lumps and for worms to start taking it down, leaving a fair tilth by spring. It also helps, when the surface organic matter is lumpy, if you knock it around in February or March with a fork, just on the surface, to smooth out the lumpy bits. Whenever you are spreading an inch or two of compost as surface mulch, break up any larger lumps, aim for golf-ball size as the largest, then weather can do the rest. I find that carrot and parsnip seeds germinate readily when sown into reasonably fine compost, then make straight roots down into the undisturbed soil below.

Maintaining abundant growth and few weeds

For vegetables, including for two crops in one year, average amounts of compost used annually are one to two inches on beds. Using less compost is possible but creates more work proportionate to results, through weeds growing, less healthy growth and smaller harvests. For paths, you can spread an inch or two of wood shavings or sawdust, or leaves, straw, bark or less rotted manure. When growing without sides, the crops in beds root happily into weed-free, mulched paths in search of food and moisture. A caveat to this is areas with slugs, where path mulches should be more decomposed, to afford less habitat for molluscs.

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Spreading compost in May after clearing winter cauliflower

Organic matter can be spread at any time of year. The most practical season is autumn, when soil is moist and still warm, so that worms can access it, and when harvests are finishing and soil is cleared of crop remains. Also, some ground becomes clear in spring after winter leeks, cabbages and so forth, and can be composted then if there is no remaining organic matter on the surface. Or you can spread compost in winter between leeks and broccoli. I find that one composting a year is sufficient for two crops, once soil is in good heart. You can tell this by how healthy and vibrant your vegetables are looking. Where to find the organic matter you need? Compost is becoming more available, and often cheaper, thanks to recycling of green waste, and there are surplus quantities of animal manure to be found in many localities, in addition to any compost you can make.

Animal manures/composts

All are suitable, at least a year old, preferably dark in colour, with lumps that can be broken up by knocking with a fork before spreading. Old animal ‘manure’ is ‘compost’ and these two words cause confusion unless one is precise. Fresh manure is not compost, but old manure is. All organic materials such as leaves can turn into compost, when stacked for sufficient time in a heap with some air. Tree leaves take up to two years to compost, or one year when added to green/nitrogenous materials such as grass. They also decompose more quickly if chopped by a rotary lawnmower. “Green waste compost” is made in facilities using shredders and turning-machinery, often sold after two months of composting, perhaps less. It reaches a high temperature which gives the black colour, almost charcoal. It’s often delivered hot and if so is best left in a heap, if you have time and space, to finish decomposing. I reckon to order and have it delivered in July, for spreading in November. When it arrives the heap temperature is often 60C/140F, and sometimes the heap needs water as it has dried out by steaming. There are no weed seeds, and nutrient status is low but satisfactory. Mushroom compost, used for growing mushrooms in undercover benches, has more nutrients than green waste compost and again may be delivered “unripe”, though it can be used at this stage. I prefer to leave it 3-4 months to finish curing. Ingredients are mostly straw and some horse manure. There used to be chalk as well but some mushroom compost does not have this now, my last batch was pH 6.8. Ask your supplier if worried, but I suggest not to worry about the pH because I have never found it to cause problems, even when I used mushroom compost of pH 9.5 on soil of pH 7.8. Don’t believe everything you read about “pH has to be ‘correct’ for different crops”. Chicken manure is unusual because of it’s high amount of nitrogen. In small amounts, say you have a few chickens, I suggest adding it to the compost heap where it helps other wastes to break down. To use it as mulch, there must have been plenty of bedding such as straw, and all of it needs to have decomposed for 6-8 months in an aerobic heap. Fresh or ‘neat’ chicken droppings are more akin to nitrogen fertiliser than to compost, and best used sparingly. Otherwise growth may be excessively leafy with more pests such as aphids. Best avoid manures (mainly horse) that have a lot of wood shavings, because they take years to decompose. However a lovely aspect of no dig is that woody mulches on the surface do not cause nitrogen robbery. Instead, problems with wood on beds are (a) the potential for slug habitat, and (b) if you spread compost a year later, the wood is “incorporated”, unless it has decomposed. So small pieces of green wood prunings of deciduous trees are good to use, preferably stacked for a year before spreading, almost compost. Of a high fungal value, the opposite of say chicken manure (bacterial mostly).

AMINOPYRALID contamination

Excellent information from the USA here.

Horse manure is at a small risk of contamination by aminopyralid weedkiller, occasionally sprayed on grass for horse-hay. Its the only weedkiller I know which persists, and it’s lethal to potatoes, tomatoes and legumes, whose growing tips become curled and twisted, see here and elsewhere on this site via the search bar.

I only heard of this weedkiller after suffering its effects in 2014, a year after I had added some horse manure to bulk up a heap of homemade compost. Potatoes, beans, lettuce, chard, alliums and cucurbits grew with deformed and stunted leaves, and matched the online photographs of damage.

I notified DOW through their website and they offered to remove the heap of compost: I declined because I wanted to find out how long the effects might last, after spreading it on some pasture.

The compost had many healthy ingredients too, and after a 12-15 months I saw no more leaf curling. If I had spread only contaminated manure, it may have taken longer to break down.

Then this spring 2019 I was gutted to see broad bean leaves curling in the same way, and traced it to compost made last summer 2018, when I had again added some horse manure to one compost heap, because of a shortage of green matter in the dry summer.

This horse manure was from the same neighbour’s stables, as I used to fill my greenhouse hotbed in February and March. This horse manure had no aminopyralid as it has been growing healthy legumes and solanums since then.

So it seems that a lot of farmers increased their use of aminopyralid herbicides in 2018. Including the Royal stables and MOD. That is the origin of problems in 2019 with Country Natural “organic horse manure”, sold by Harrington & Jessups.

I did some trials with this compost, with susceptible pea and bean seeds, also tomato plants and basil. All grew in a stunted way and the basil died, compared to healthy growth of the same seeds and plants in a purchased and Soil Association certified compost.

I made a video about these problems, to help gardeners identify the problem in case they have it. There are hundreds of comments to this video and many are “So that is the problem with my tomatoes/sunflowers/beans”.

The poison has many points of entry to gardens, all invisible:

  • horse manure from stables where horses ate hay sprayed with weedkillers such as Banish, Forefront, Grazon Pharaoh and Runway. Or if horses were bedded on rape straw sprayed with Astrokerb.
  • hay used by gardeners, as above
  • horse manure used in commercial bagged compost for mulching: I have heard several horror stories after purchases of Country Natural organic manure.
  • potting composts which have used contaminated horse manure or green waste composts, such as some bags of New Horizon and Jacks Magic, for example I saw the latter when giving a course in Cheshire
  • mushroom compost if it contains contaminated horse manure
  • green waste compost if some of the grass mowings were from lawns sprayed with weedkiller containing clopyralid, which affects growth similarly to aminopyralid. My local composting operation are starting trials of all batches with pea and red clover seeds, but this is expensive because of adding time to their process.
  • Bed-Down Rapasorb chopped Rapeseed straw, from Astrokerb – the NFU warns farmers in no uncertain terms, not to use or sell this for bedding
  • gardens and allotment sites close to fields sprayed with weedkillers containing aminopyralid weedkiller, as in this link on my website forum.

Has this happened before?

Many gardeners suffered the same problems in 2008 and 2009, after which the pyralids were temporarily withdrawn, before being sold again but with a protocol of notification to all buyers of products such as hay, if they have been treated.

However this appears to happen rarely, so we are all left guessing.

What can gardeners do?

Because of the lack of a paper trace, it’s buyer beware for manures and composts. Even some cow manure is contaminated, as per this blog from a Dublin allotment site.

Should your plants show the symptoms, your options of disposal are few apart from sending plants and compost to landfill. If you send them to recycling, they will contaminate the green waste compost.

If you spread contaminated compost/manure on the surface, I would remove it to landfill. If you dug in the product, it will take a year or two to break down and for growth to approach normal again, although there is no fixed time period it appears. Dow advise repeated cultivation but I disagree because this damages the very organisms which do valiant duty in dissipating the poison.