Aubergines are tricky to grow outdoors in the UK, but they do very well in a polytunnel or greenhouse. While growing aubergines require very similar conditions to those needed for peppers and tomatoes, they need a longer growing season. For the best chance of success, start the seeds as early as possible or buy young plants from a professional nursery.
Plant the seeds roughly 5mm below the surface in modules during February or March, but make sure you have the right conditions to support their growth – warmth, and plenty of light. Aubergines are picky plants and will sulk if given a chance. If you don’t get around to sowing seeds until April, it’s getting too late. Aubergines can be attacked by emerging aphids even very early in the year, so be sure their potting medium is sterile. If they get too big before the weather has warmed up enough to plant them out, pot them on into something larger. Don’t let them get root bound, or their growth will be affected for the entire season.
Aubergine roots aren’t as delicate as those of courgettes so they don’t have to be sown in biodegradable pots, but do try to disturb them as little as possible when transplanting.
Aubergines are hungry plants, so the beds where they are to be grown should have plenty of well-rotted compost dug in at least a couple of weeks before planting. They favour light, well drained soil. When the weather has warmed and all danger of frost has passed – usually in May – set them out into their final positions. They need a sunny, sheltered spot with no competition, so keep the area weed-free, and add a mulch to conserve soil moisture near the surface. While aubergines don’t have to have sunshine all the time, don’t grow tall plants nearby! They don’t do well in cool conditions either, which is why they are rarely successful outside in the UK.
Growing aubergine plants is relatively easy, but getting them to produce a worthwhile crop can be another matter entirely. If you check gardening blogs online you’ll find plenty of references to flowers repeatedly turning brown and dropping from the plant with no fruit forming at all. Aside from the more obvious factors such as warmth and sunlight, ventilation is a key factor in fruit formation. Leaves on a mature plant are big and will restrict air flow, causing flowers to drop without forming fruit. Trim the central leaves away so that air can circulate, and make sure the plants do not run short of water during this critical period.
Later in the season mould can take hold and spread quickly. Again, ventilation is a key factor in preventing this, and if you see any sign of it – brown splotches on the leaves, bits of flowers stuck to developing fruit – deal with it right away.
Once five or six flowers have set fruit, nip of any others so that the plant concentrates its energy into ripening those that are left. If you allow them to set more fruit it’s possible that none will be ready before the cold weather hits. The fruits are heavy, so the plants will need supporting with canes.
If everything goes well you could be eating aubergines as early as mid-June. The harvest should continue until the cold weather kicks in, but under cover that still means you could be picking your last fruit as late as November. Pick fruit when it’s still glossy, as a dull coat indicates it’s been left too long. If frost threatens, cut the plant down and hang it upside-down in a frost-free spot, and the remaining fruit will continue to ripen.
Aubergines can be cut into 1cm slices, blanched for a couple of minutes in boiling water and then dried, or frozen in ratatouille or lasagne. They don’t freeze well on their own.
Aphids, a serious pest especially if they get a foothold early in the year, red spider mites and whitefly.