Eggplant

Light and exposure

The eggplant demands full sun and constant heat. Give it the warmest, brightest spot you have: a greenhouse, a tunnel, a conservatory, or failing that the foot of a wall that takes the midday sun and releases heat at night. Below six hours of direct sun, the fruits do not set.

Where summers stay cool, growing under cover changes everything. A greenhouse or a tunnel easily gains five to eight degrees over the outside air and shelters the plant from the cool wind. In open ground, reserve the most favourable microclimate for it and only expect a good harvest in truly hot summers.

Watering

The eggplant drinks a lot. A plant loaded with fruit transpires enormously in strong heat, and the slightest water stress aborts the flowers or gives bitter, fibrous fruits. Water regularly and generously at the base, without ever letting the soil dry out completely between two waterings.

Water in the morning, with water that is not ice-cold, and avoid wetting the foliage. Under glass, the heat dries the substrate fast: in a heatwave, a daily watering is not too much. A mulch at the base keeps the coolness in and smooths out the swings, which the plant hates above all.

Soil and repotting

The eggplant wants rich, deep, well-drained and above all warm soil. Amend generously at planting with mature compost or decomposed manure: it is a hungry plant that produces all season long. Heavy, cold soil brings it to a halt.

Plant nothing before the soil has really warmed up, never before the last frosts and only under cover where spring stays cool. Space the plants at least fifty centimetres apart, they become bulky. In a pot, count on at least ten to fifteen litres per plant, a dark container that heats in the sun, and a rich potting soil supplemented with fertiliser during fruiting.

Temperature and humidity

This is where everything is decided. The eggplant only really gets going above 20 degrees and does best between 22 and 28 degrees. Below 15 degrees it stalls, the flowers drop, and the slightest frost kills it. It is more cold-sensitive than the tomato, which explains why it so often fails outdoors in a cool climate.

Sowing requires bottom heat: it takes 24 to 27 degrees at seed level for a proper emergence, hence the use of a heat mat and supplementary light in late winter. Do not put any plant out until the last frosts have passed, and keep a fleece for the cool nights of early season. Under glass, ventilate as soon as it gets muggy to avoid excess humidity.

Pruning and upkeep

The eggplant bears heavy plants that bend under the weight of the fruit: stake each plant from planting, or train it on a wire under glass. Without a stake, the branches break once loaded. Pinch out the top above the second or third flower to force branching.

Where the season is short, limit the number of fruits. A plant trying to carry eight or ten will fatten none before the end of the season. Keep four to six fruits per plant, remove the late flowers that will never have time to ripen, and take off the suckers and the leaves that smother the centre to let air and light through.

Pests and diseases

Under glass, the red spider mite is the number one enemy: it thrives in hot, dry air and stings the foliage, which mottles then dries out. Dampen the atmosphere and check the underside of the leaves. Aphids colonise the young shoots, and the whitefly readily settles under cover.

The Colorado beetle attacks the eggplant as it does the potato: pick off adults, larvae and orange egg clusters by hand as soon as they appear. As for diseases, excess humidity favours botrytis, that grey rot on stems and fruits, and a soggy or cold soil opens the door to damping-off and collar diseases. Ventilate, water at the base, do not let water stagnate.

Propagation

The eggplant is propagated by sowing, and you must start very early because growth is slow. Sow indoors eight to ten weeks before the planting date, at 24 to 27 degrees on a heat mat, under supplementary light. Emergence takes one to three weeks. Prick out into pots as soon as there are two true leaves and keep the young plants nice and warm and bright.

Transplanting under cover happens once the last frosts have passed, when the plants are stocky and the soil has warmed. Choose early varieties, better suited to short summers. Saving your own seed is possible from a very ripe fruit left to yellow, but start from reliable seed so as not to add chance to an already difficult crop.

Toxicity

The fruit is edible and harmless. As with all nightshades, the foliage and stems contain solanine and are not to be eaten.

Month-by-month care calendar

Green Hub tips

• Without a greenhouse or a tunnel, the eggplant is a gamble wherever summers stay cool. A wall that takes the midday sun and a hot summer are the minimum to hope for a harvest.
• Limit to four or six fruits per plant. Loaded with more, the plant fattens none before the end of a short season.
• Sow very early, eight to ten weeks before planting, and at 24 to 27 degrees. Without bottom heat and supplementary light, the seeds come up poorly and the plants drag.
• Under glass, watch for the red spider mite on the back of the leaves. Dampen the surrounding air, it hates humidity and loves dry heat.