Clear Weeds for a New Garden Bed in Six Steps
By Charles Dowding and Stephanie Hafferty
Preparing soil for growth is about clearing weeds, including the roots of perennials that may be invisible during winter. Vegetables in particular are hungry plants: they need soil to be free of weeds and also well-fed.
Mulches made of compost feed the soil while clearing weeds, and allow you to grow food at the same time that weeds are expiring in darkness; other mulches such as polythene are useful for persistent weeds.
Here’s the six-step, no-dig process that we’ve consistently used to clear weeds from the soil while growing healthy vegetables at the same time.
Step 1: Feed the Soil
Vegetables are hungry plants and have the potential to reward us with abundant growth, in undug and well-fed soil, without using any synthetic feeds or fertilizers.
Mulch with organic matter to feed the soil in general, rather than plants specifically. It’s an important difference, unknown to salesmen of fertilizers.
Soil fed with organic matter holds nutrients in stable, water-insoluble form, like a well-stocked larder. Then, when growing conditions arrive and coincide with plant roots seeking the means to grow, soil organisms increase in vigor and help roots to access nutrients, and moisture too. In my garden, I recently experimented with applying different types of mulches to different areas.
On some of the area, I spread a 4in (10cm) layer of less decomposed cow manure that contained some yellow straw. At this stage, you can also use leaves and wood mulches that are partly but not fully decomposed. On another area, I spread the contents of a greenhouse hotbed, made 10 months earlier from horse manure. It was 50-70% wood shavings that looked similar to when the heap had been filled.
I applied all these mulches in midwinter and by early spring many of the less vigorous grasses were dead or dying, while the couch grass, creeping buttercup, and dandelion were starting to push their leaves through. I could have spent time removing them with a trowel, perhaps spreading another 5cm (2in) of finer compost on top, for planting into, but in this case, I laid a light-excluding mulch on the surface.
Step 2: Lay a Weed-Suppressing Cover
I used different materials, mostly 600 gauge polythene which I had bought cheaply from a farmer after it had covered his lambing polytunnel for 11 years. The wind had caused some splits but there were still large pieces useful for mulching.
There was not quite enough polythene, so in one area I laid cardboard and then landscape fabric on top. They combine well because the card stops weeds growing, as long as you overlap edges by 4-6in (10-15cm), while the membrane keeps it in place. This saves having to secure the cardboard’s edges with weights such as stones, which cause decomposition underneath them, allowing weeds to find light and regrow.
Step 3: Grow Through the Covers
What you can grow depends on the material, your climate, the weeds, and any soil pests. We always have slugs underneath polythene and cardboard, so there is no point in planting salads, chard, brassicas, or beans. Plus, these vegetables need close spacing that would mean a lot of holes in the polythene and cardboard, allowing perennial weeds to grow into the light.
So the best options are widely spaced vegetables that tolerate some slug damage. I enjoyed success with potatoes, courgettes (zucchini), and winter squash.
To plant potatoes in mid-spring, I cut crosses in the covers at 45cm (18in) spacings, and used a trowel to slot tubers below the 10-15cm (4-6in) compost mulch, nestling at soil level. For the squash and courgette plants in late spring, I cut round holes of 10cm (4in) diameter, 60cm (2ft) apart, and used a trowel to make holes for pot-grown plants.
Step 4: Remove Small Weed Leaves that Appear Through the Planting Holes
Doing this will help ensure that weed roots underneath the mulch are not fed by photosynthesis. How often you need to do this depends on the weed roots, but by autumn, most will be dead, except if there are bindweeds and marestail (Equisetum arvense).
The first potato stems may struggle to find their small slits or holes in polythene and need guiding through; after that, they grow easily. Cucurbits quickly cover an area, provided you plant them in warmth, say a week after the last frost.
Step 5: Harvest
Potatoes grown this way are best gathered as soon as their leaves are half yellow, before slugs damage the tubers. The date of harvest depends on the type of potato, around midsummer for second earlies and late summer for maincrops. Cut off the haulm to compost (even if it has some blight) and pull back the polythene cover, which can be reused. Potato tubers lie near the surface and you can gather them without digging, perhaps using a trowel for some that are more buried.
To harvest squashes, cut them carefully after most leaves have died in early autumn when the fruits’ skins and stems are turning dry and hard.
Step 6: Clean the Soil
In our experience, by late summer the couch grass and other weeds had all died, only some weak bindweed persisted, and we pulled out its surface roots to compost, after removing the covers. The surface was level, soft, and weed-free, ideal for a late summer planting of mustard salads, to crop through autumn and winter.
In December I created raised beds by scraping the top 5-7cm (2-3in) of compost and soil from what became 18in (45cm) pathways, onto what is now the 1.2m (4ft) raised beds. There is no need for wooden sides.
In Closing
When soil is clear or mostly clear of perennial weeds, growing is easier and you can be more creative with sowings and spacings. The most important thing is to maintain soil fertility and to keep weeds in check. Surface mulches of organic matter achieve both of these.
This excerpt is from No-Dig Organic Home & Garden by Charles Dowding and Stephanie Hafferty (Permanent Publications, 2017) and is reprinted with permission from the publisher.
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