Cucumber

Light and exposure

The cucumber wants full sun and a maximum of heat. Give it the warmest and brightest spot in the vegetable garden, sheltered from the wind that snaps the stems and chills the plants. It needs at least six to eight hours of sun a day to produce.

Here, growing it under a greenhouse or tunnel makes all the difference: the heat missing in the open air is trapped there, and the plants stay sheltered from the damp that lingers in the evening. In open ground, reserve it a south-facing wall, which gives back the heat stored during the night.

Watering

It is a heavy drinker. The soil must stay cool at all times, never drying out between two waterings. Water regularly and generously, always at the base of the plant and never on the foliage: leaves wet in the evening, in our damp late summers, call up powdery mildew for certain.

Consistency counts as much as quantity. A cucumber that suffers jolts, soil that dries then a big watering, produces bitter fruit. A mulch at the base keeps the moisture, limits evaporation and prevents the soil from drying out in strong heat.

Soil and repotting

The cucumber needs soil rich in humus, deep, cool but well drained. Work the earth by incorporating mature compost or well-rotted manure before planting: this crop is greedy and grows fast when it is fed. Poor soil gives puny plants and little fruit.

Plant after mid-May, when the soil has warmed, one plant every fifty to sixty centimetres. In a greenhouse or a pot, choose a container of at least thirty centimetres with good drainage at the bottom, and a rich compost with added compost.

Temperature and humidity

This is the critical point in Belgium. The cucumber grows well between 20 and 25 degrees and already suffers below 12 degrees: growth stops, the leaves yellow. It tolerates no frost and hates the cold nights at the start and end of the season.

Do not trust a mild April, the late frosts still strike until mid-May. Sow warm indoors, between 20 and 25 degrees, and only put the plants out once that hurdle is past. In a greenhouse, the air humidity can climb quickly: ventilate during the hot hours to avoid the stuffy climate that favours disease.

Pruning and upkeep

Train the plants up a vertical support, a string, a mesh or a net. You gain space, the fruit stays clean and straight, and the air circulates better between the leaves, which limits disease. Tie the main stem as it climbs.

Harvest regularly and young, as soon as the fruit has reached a good size, without waiting for it to yellow. The more you pick, the more the plant produces: a fruit left to swell stops the formation of the next ones. Cut with secateurs rather than pulling, so as not to damage the stem.

Pests and diseases

Powdery mildew is enemy number one in our climate. It is recognised by a white powdery felt on the upper side of the leaves, which end up drying out. It settles in quickly as soon as the nights cool and the humidity rises, typical of our late summers. To delay it, water at the base in the morning, ventilate the plants and space them out.

As for pests, aphids colonise the underside of the leaves and weaken the young plants. In a greenhouse, watch out above all for red spider mites, which proliferate in hot, dry air and prick the foliage with fine yellow spots: a misting of clear water and good ventilation keep them at bay.

Propagation

Sowing is the only practical route. Sow warm indoors, between 20 and 25 degrees, from April to May, two or three seeds per pot laid on their side at one centimetre deep. Emergence takes five to eight days. Keep only the most vigorous plant per pot.

Transplant without waiting too long, because the cucumber hates having its roots cramped. Harden off the young plants a few days before setting them out by putting them out during the mild hours, then plant outdoors or under a greenhouse after mid-May. Handle the rootball with care, this plant tolerates having its roots disturbed poorly.

Month-by-month care calendar

Green Hub tips

• In our climate, a greenhouse or tunnel changes everything: it is heat that the cucumber lacks in the Belgian open air. Without a greenhouse, press it against a south-facing wall.
• Water regularly and at the base, never on the foliage. Watering jolts make the fruit bitter, and leaves wet in the evening call up powdery mildew.
• Train it up a vertical support: clean and straight fruit, saved space and better ventilation against disease.
• Pick young and often. A cucumber left to swell on the plant blocks the formation of the next ones.