Nearly every crop lost in a British garden goes to one of about six problems, and every one of them has a physical answer that works better than a spray would.
The approach is not organic purity for its own sake. It is that barriers and timing are more reliable, cheaper, and do not need reapplying after rain.
The three that work
Healthy plants also resist better. A well-fed plant in good soil with enough water shrugs off damage that kills a struggling one, which is another argument for soil and compost.
Slugs and snails
The biggest problem in British growing by a wide margin, and the one that decides whether a bed of young plants survives.
When it matters: the first fortnight after planting out, and any seedling. An established plant tolerates slug damage; a transplant does not survive one night.
The night patrol is the answer. Go out an hour after dark with a torch, on a damp evening, for the fortnight after planting out. You will be astonished how many there are. Half an hour on three consecutive nights makes a visible difference to a bed for the rest of the season.
Plant out big. Module-raised plants with several true leaves survive what direct-sown seedlings do not. This one change saves more plants than any product.
Remove the habitat. Long grass at the bed edge, boards, pots, stones, and dense low planting are all slug hotels. Bed edges are where they live.
Encourage the predators, which are the real long-term answer: hedgehogs, frogs, toads, slow worms, ground beetles and thrushes all eat slugs in quantity. A pond is the single best thing you can add to a garden for this. Ground beetles live under stones and in rough grass, so leave some.
Water in the morning, not the evening. A bed watered at dusk is a damp bed all night, which is exactly what slugs want.
Aphids
Greenfly and blackfly. Alarming in appearance and usually less serious than they look.
- Squash them, or wash them off with a jet of water. On a small scale this is entirely adequate.
- Pinch out the tips of broad beans once the first pods have set. Blackfly go for the soft growing tip, and removing it removes the problem and improves the crop.
- Predators arrive, but late. Ladybirds, hoverfly larvae, lacewings and small birds all eat aphids in quantity, and they build up after the aphids do rather than before. Tolerating an early outbreak is what allows the predator population to establish.
- Do not spray anything broad spectrum, including soap solutions, over a whole plot. It kills the predators as well and you end up on a treadmill.
- Grow flowers among the vegetables. Umbellifer flowers, poached egg plant and marigolds all feed hoverflies and parasitic wasps.
- Check for ants, which farm aphids for honeydew and actively protect them. Dealing with an ant trail sometimes deals with the aphids.
Ants are also a sign rather than only a cause, and a plant that is repeatedly aphid-ridden is often stressed, over-fed with nitrogen, or in the wrong place.
Cabbage white and pigeons
Together these will remove a brassica bed entirely. See brassicas through winter.
Cabbage white butterflies lay from about May to September, and the caterpillars strip a plant in days.
- Fine insect mesh from the moment of planting out is the only reliable control. The butterfly cannot lay through it.
- Hold the mesh clear of the leaves on hoops. Anything touching the leaf gets eggs laid through it.
- Otherwise, inspect the undersides of leaves every few days and squash eggs and caterpillars. This works and it is a real commitment.
Pigeons are the winter problem and they are worse than most people expect.
- Net properly, with the netting held clear and pegged down all round.
- Use a mesh small enough that birds cannot become trapped, and check it regularly, because netting that entangles wildlife is both cruel and unlawful to leave.
- Scarers work for a fortnight and then are ignored.
Carrot fly
A small low-flying insect that finds carrots by smell and lays at the base, and the larvae tunnel through the root.
- A barrier 60 to 75 centimetres high of fine mesh or fleece around the bed works, because the fly flies low and will not go over it. This is the classic and it is effective.
- Or cover the bed entirely with fine mesh.
- Do not thin carrots on a still evening. Thinning releases the smell that attracts them, so do it in the evening, remove the thinnings entirely, and water afterwards.
- Sow thinly so thinning is barely needed, which is the neatest answer.
- Timing helps. Sowing after early June misses the first generation.
- Resistant varieties exist and reduce rather than remove the problem.
Parsnips, parsley and celery are affected too, being the same family.
Other common problems
- Flea beetle peppers the leaves of rocket, radish and brassica seedlings with tiny holes. Fleece over young plants, keep them well watered, and they grow through it.
- Leek moth and allium leaf miner are increasing in Britain. Fine mesh over leeks and onions from planting.
- Codling moth in apples: pheromone traps, and gather and destroy fallen fruit.
- Wireworm in newly broken grassland, tunnelling into potatoes. It reduces over a few years of cultivation; lift maincrop promptly rather than leaving it in the ground.
- Blight on potatoes and tomatoes is the biggest disease problem. See potatoes.
- Mice take pea and bean seed the moment it is sown. Start them in modules and plant out, which removes the problem entirely.
- Rats follow poultry feed and compost containing cooked food. See pest-proof food and waste storage.
- Badgers and deer need real fencing or nothing. Half measures waste money.
- Cats treat a freshly raked seedbed as a litter tray. Twiggy prunings laid over the bed until the seedlings are up solves it.
Encouraging the predators
The slow answer that gets better every year, and it costs almost nothing.
- A pond, however small. Frogs and toads eat enormous numbers of slugs, and a washing-up bowl sunk in the ground with a slope out of it will do. This is the single highest-value addition to a productive garden.
- Leave some rough corners: long grass, a log pile, a pile of stones. That is where ground beetles, slow worms and hedgehogs live.
- A hedgehog gap in the fence, 13 centimetres square, so they can move between gardens. A hedgehog needs a range far larger than one garden.
- Flowers among the vegetables, especially open flat ones that small insects can feed from.
- Birds: feed them in winter and they stay through spring, when they are picking caterpillars off your brassicas.
- Do not use slug pellets or broad spectrum sprays, which move up the food chain and remove the predators you are trying to build.
Expect a lag. In year one the pests arrive and the predators do not. By year three the balance is noticeably different, and this is the main practical argument for not reaching for a quick fix.
Tolerance
The part that is not a technique.
Some damage is fine. A few holes in a cabbage leaf, some aphids on a bean tip, a slug-nibbled lettuce. None of that reduces the harvest meaningfully, and chasing a perfect crop costs more time and does more harm than accepting an imperfect one.
Decide what you actually cannot lose:
- Transplants in the first fortnight. Protect these properly.
- Anything you only have a few of.
- The winter crops, because there is no second chance at those.
And what you can share:
- Established plants in midsummer, when there is plenty.
- The outer leaves of anything.
- A proportion of the fruit.
Grow a bit more than you need and the arithmetic solves itself. That is cheaper than any control measure and it is what gardeners have always done.