Fewer weeds in no dig
Whenever soil is dug, loosened or turned over, it recovers from the disruption by re-covering with weed growth – both from roots of perennials and seeds of annuals. By contrast when left uncultivated it has less need to re-cover and therefore grows less weeds, as shown by a look at Homeacres at any time of year.
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, small but still important.
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.
Soil condition, firm is good!
Soil compaction is thankfully rare. 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.
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.
Its 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.
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.
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.
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, 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.
- 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.
- 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.
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.
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.
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.
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).
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 its lethal to potatoes, tomatoes and legumes, whose growing tips become curled and twisted, see here and elsewhere on this site via the search bar.