Growing Cucumber

The cucumber belongs to the cucurbit family and has been grown for more than 3000 years. Like the aubergine, it comes from India. That explains its need for warmth.

Some cucumber varieties only do well in a greenhouse, and that covers most long salad cucumbers. These are the typical long, smooth cucumbers you find in the shops.
Then there are field cucumbers and gherkins, which you grow outdoors lying on the ground. A few long salad cucumber varieties cope outdoors too, but out there they need a support to climb up.

Field cucumbers, gherkins and some outdoor-suited long salad cucumbers can go straight into the bed from the second half of May, as soon as the soil feels warm. Cucumbers only germinate from about 13 degrees, and they get going quickly at a soil temperature of 20 to 30 degrees. Sow the seeds 2 to 2.5 centimetres deep. Plant out raised seedlings only after the last frosts, so towards the end of May, once they have two strong seed leaves and the first proper leaf. Don't set them deeper than they sat in the pot, as a buried root collar rots easily. Outdoors the cucumbers need about 100 centimetres between the rows and 40 centimetres within the row, so a bed 1.20 metres wide has space for one row.

In a heated greenhouse you can start a month earlier. Spacings there are more generous, about 130 x 45 centimetres, and the cucumbers climb up strings or nets. That works outdoors too, for example on a frame where you fix a wide-mesh grid at an angle. The space underneath then stays free for lettuce, which is grateful for a bit of shade in high summer. Find the cucumbers a sunny, sheltered spot and work in plenty of compost or half-rotted manure beforehand.

Cucumbers are hungry feeders and even like coarse compost and half-rotted farmyard manure spread before planting. An occasional drink of comfrey liquid feed or comfrey tea does them good too.

Above all, though, a steady water supply matters. Cucumber plants don't like cold water. If they run short of water, the fruits turn bitter and no longer taste good.

The most common cucumber disease in the garden is downy mildew. From July onwards, after cool, dewy nights, yellow, sharply defined spots appear on the leaves and soon turn brown. So water only at the base of the plants, and early enough that the leaves go into the night dry. Train the cucumbers up a frame or mulch the soil.

Powdery mildew, with its white coating that wipes off, shows up more in dry warmth and in the greenhouse. Young leaves mottled light and dark green, along with deformed fruits, point to cucumber mosaic virus, which aphids pass on. Pull those plants out; a protective net until flowering keeps the aphids away.

Angular yellow-brown leaf spots or sunken dark patches on the fruits come from bacteria and fungi that arrive with the seed and survive on plant debris. Clear diseased plants away completely and leave four years before any cucurbit returns to that spot. In the greenhouse, spider mites cause trouble in heat and dry air, and predatory mites help against them. Slugs love young cucumbers, so protect the young plants well.

If your cucumbers suddenly wilt in August even though the soil is moist and the leaves are green, black root rot is often behind it. The fungus sits in the soil and survives there for several years. Only put cucumbers back on the same bed after four years, and not after squash, courgettes or melons either.