If it’s time to weed, it’s time to seed (Bare-bum test optional)

There was a time – typically on the first dry, sunny day of mid-spring – when I would saunter out into the kitchen garden to sow vegetable seeds, with nary a thought as to how to keep the emerging plants protected from weeds, pests, diseases and late frosts.

But there’s nothing like failure to teach you to be more circumspect.

One of the first lessons I learned is that seed sown into cold, wet soil is far less likely to germinate than when sown into ground warmed and dried by a decent stretch of mild, sunny weather, so that it’s above seven degrees. As to the thorny question of how to gauge this, some gardeners advocate the “bare bum test” (not really my thing), others wait for the blackthorn blossom to fade, but I’ve found that the simplest method is to watch for the appearance in the garden of emerging weed seedlings – always a reliable sign that conditions are right for germination.

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Dahlias in flower. Photograph: Richard Johnston

Even then, I increasingly choose to sow many of my vegetable crops into modules or lengths of old guttering filled with seed compost, rather than directly into the ground. Placed somewhere sheltered, sunny and at a height – I have an old trestle table for this purpose – it’s a much easier way of protecting young seedlings from weeds, slugs and searing cold winds until they’re established enough to be planted directly into the ground. That way, when a late frost or leaf-shredding hailstorm threatens, it’s a simple matter of covering the containers in several layers of horticultural fleece.

If you have a glasshouse or polytunnel in which to put them, then all the better- just make sure to keep it very well ventilated on sunny spring days, when temperatures can quickly soar.

In the meantime (crops such as potatoes, onions and shallots aside), I’ve found that there’s plenty to be getting on with in the kitchen garden/ allotment in early April in terms of planning crop rotation and getting soil conditions just right for optimum growth.

If you were organised enough last autumn to cover the ground in a weed-suppressant mulch and/or a layer of plastic sheeting, then much of the hard work is already done. Just lift the plastic away and inspect the underside for any lurking slugs or snails (kill these by means of a quick chop with a scissors/ a quick crunch underfoot) before replacing it until you’re ready to use the ground.

Not only does plastic sheeting help to keep beds clear of weeds as part of the no- dig method, but it also helps to dry it out, insulates it and enhances the warming effects of the sun’s rays. Some gardeners like to use transparent sheeting (the kind used to cover polytunnels) rather than opaque black plastic, for the reason that the former allows any dormant weed seeds hiding in the top layer of soil to germinate before being easily hoed away. Others prefer black plastic, not only because it has better thermal qualities but also because it suppresses weed germination and helps trap slugs. Both have their benefits.

If you didn’t get round to preparing vegetable beds or allotments last autumn, then now is the time to do it, making sure to remove all existing weeds. Finish off with a thin layer of garden compost and a sprinkle of seaweed dust, covered with the aforementioned protective layer of plastic, its edges buried to secure it against strong winds. Left on the ground for just a couple of weeks, this will make a world of difference to germination rates as well as the successful establishment of baby transplants.

In cold or exposed gardens, you can offer your crops further protection against the vagaries of an Irish spring as well as pests by sowing and/or growing them under a layer of fleece, or under homemade miniature hoophouses constructed from timber and flexible lengths of wavin piping covered in clear plastic or Enviromesh.

Weeds are another threat to many food crops, depriving them of light while offering safe harbour to pests, as well as acting as host plants for diseases. So do your best to start the growing year with clean veg beds. Dig out the roots of any persistent perennial weeds, hoe away any emerging annuals and try not to accidentally introduce weed seeds via contaminated manure or garden compost (the reason I don’t add weeds to my compost bin).

As mentioned earlier, keep any cleared ground under cover either by mulching it or sheeting it in plastic. To keep freshly sown or newly planted beds weed-free, mulch any bare ground (use a layer of garden compost or dampened, fresh grass clippings taken from a tightly mown lawn). Alternatively, plant into holes cut/ burnt in black Mypex. Both methods are very effective as long as you make sure to take ongoing precautions against slugs.

Above all else, try to prevent weeds from setting seed, bearing in mind that time-proven maxim that “one year’s seeding is seven years’ weeding”. Seven years’ weeding. Perish the thought.

This week in the garden

Seedlings If you sowed seed of annuals or perennials under cover earlier this spring, start pricking out the young seedlings into modules or individual small pots to give them space to develop. Always handle baby seedlings with great care when pricking them off: hold them gently by the leaves, never the stem; use a seedling dibber or slender stick to carefully separate the root system; make sure to water it very gently immediately after transplanting, and make sure to protect them from the cold.

Dahlias Dahlia tubers lifted and stored over the winter need to be divided before being potted on and replanted this spring, otherwise both the quality and quantity of flowers produced starts to decline. Use a sharp knife, and always leave a short length of stem attached to each division so that it has "eyes" (the growing points of the plant) capable of producing new shoots.

Sweet pea Plant autumn/winter-sown young sweet pea plants (pictured) out into the garden, making sure to give them a cool, rich soil in full sun. While these are surprisingly hardy, it's worth protecting them with a layer of horticultural fleece is especially cold weather threatens.