Gardening: Natural justice

When your carefully nurtured seedlings start being devoured by pests, it's tempting to use chemical insecticides. Don't do it, says Sarah Raven - organic methods can be just as effective and your garden will be healthier in the long run but your garden will be healthier in the long run

I HAD MY first real test as an "organic" gardener last week. I grow cut flowers on a semi-commercial scale for the flower- arranging courses I run, and supply the farm shop with 40 bunches a week. In September the farm begins its conversion to full organic status (a three-year process) and I want to include the fields and garden where I grow these flowers in the scheme.

It's not going to be easy. Last Sunday, I went out to water a new area of garden. It had been ploughed up in the autumn and we have spent the spring rotavating and digging in lorry-loads of grit, mushroom compost and manure. I have been growing lots of plants from seed, and lines of nascent larkspur, cosmos, Atriplex and sunflowers had gone in, interspersed with carrots, lettuce and broad beans. But the larkspurs were looking ill. They were floppy and the leaves around the edges of the new plants were turning yellow. When I dug around the seedlings with a trowel, the whole plant came up in my hand, severed at ground level from its root. It was gut-wrenching. Perennials produce more leaves and flowers if cut down to ground, but not annual seedlings. I'd spent two months raising this stuff from seed, and now at least half the seedlings were dead. They'd only been in the ground 10 days.

When I looked more closely, I noticed that some of the plants were sawn right through at the neck, with yellow-brown, inch-long worms poking out of the end of the cut stem. Other plants were still attached to their roots, but three-quarters of their stems had been eaten.

I looked them up in the best book I know on the subject: Pippa Greenwood and Andrew Halstead's RHS Pests & Diseases (Dorling Kindersley, pounds 17.99). The pests responsible for severing the plants completely were wire worms, the larvae of the click beetle (Agriotes lineatus). The others were leather jackets, the larvae of "daddy-long-legs". These are disgusting, like huge slate- grey maggots.

What could I do? I wanted to wipe them out. I rang Green Gardener (details below), the experts in dealing with pests organically, to try to find a biological control, but there isn't one for either of these two. The only way to get rid of them is to use a chemical called Gamma BHC. I couldn't bring myself to use that as it contains lindane and would leave a poisonous residue in the soil for years, or even decades.

To garden well organically, you have to practise good husbandry, gardening for health rather than the one-shot zapping of disease. If I'd known my stuff I would have realised that both wire worm and leather jackets would be a problem. They are always present in newly ploughed grass. I should have potted on the plants one more time and planted out the seedlings when they were more mature. It was the young, rather weedy seedlings that were being eaten. The wire worms like the sweetness of the young growth. If I'd left planting until the end of May, I would have avoided the wire worms' main feeding season from the middle of March until the end of May and saved every plant. And larkspurs were a disastrous choice. They are temperamental and hard to get going. I would have been fine with broad beans, French beans, spinach or sunflowers. They hate the taste.

These weren't the only invaders. The buds of my sweet Williams were covered in a haze of aphids; the snails had wiped out a section of my dwarf runner beans and scarlet beetles had left holes in the leaves of my Asiatic lilies. A few cabbage white butterflies hovering in the garden made me anticipate their feasting caterpillars.

There is no need to despair, or to resort to toxic chemicals, though. None of these bugs is devastating if you keep on top of the problem, and there are an increasing number of biological controls to help you.

The lily beetles are brilliantly obvious with their cherry-red wings. Just pick them off and squash them when they come out to feed in the early morning. Snails can also be harvested when they're feeding in the dark. I feed mine to the ducks, but they could be tied up in a bag and put in the bin. Cabbage white caterpillars will chomp their way through a whole bed of nasturtiums, cleomes and verbascums, as well as your cabbages: check underneath the leaves of your brassicas and scrape off any eggs. Pick off any caterpillars and drop them into a jar of paraffin. This is more time-consuming than zapping the lot with insecticide, but we should all be doing it.

From the number of aphids in the garden here, it looks as if it might be a bad year for them. Spray affected plants with soft soap, a natural, organic insecticide. You should encourage lacewings too (these are wiped out by chemical insecticides). One lacewing larva will eat its way through 300 aphids before it hatches. Green Gardener supply larvae to sprinkle over your plants and you can also buy lacewing chambers from them. They contain straw impregnated with a natural pheromone that draws the lacewings in. Without these houses, 95 per cent of lacewings die in the winter cold, but with them, the population will gradually expand and keep aphids in check forever.

Green Gardener: 41 Strumpshaw Road, Brundall, Norfolk (01603 715096)

- We've just planted out some runner beans and made them a corridor of 8ft canes to grow up. It makes an excellent architectural addition to the vegetable plot which you don't get with the more usual 6ft kind.

- You need to think of screening your greenhouse from the heat and glare of midsummer sun. Buy some green plastic sheets from the garden centre to save your tomatoes and aubergines from being frazzled as they grow.

- By now, your tulip, narcissi and fritillary foliage should be brown. Its important not to tidy it up until it is, so that the bulb can carry on photosynthesising and storing food for lots of flowers next year. Give them a potash-rich feed to help with food synthesis and storage and remove any decaying foliage. Leaving the leaves on top of the soil encourages the proliferation of tulip blight. This causes the interesting feathering that flamed Tulipomania in Seventeenth century Holland, but will weaken the bulbs.

This week

1 Screen your greenhouse from the heat and glare of midsummer sun with some green plastic sheets from the garden centre. These will save your tomatoes and aubergines from being frazzled as they grow

1 By now, your tulip, narcissus and fritillary foliage should be brown. It's important not to tidy it up until it is so that the bulb can carry on photo- synthesising and storing food for lots of flowers next year, but leaving decaying foliage on top of the soil encourages the proliferation of tulip blight, which will weaken the bulb. Give them a potash-rich feed to help with food synthesis and storage

1 Make a corridor of 8ft canes for runner beans to grow up. The more usual 6ft kind don't create such an interesting architectural feature