Cucumbers Growing Guide
Cucumbers are tender climbing or scrambling plants, for growing in a greenhouse or a warm sunny site outdoors, either up supports or trailing on the ground. With enough warmth and plenty of water, they’ll produce lots of tasty, crunchy, refreshing cucumbers from mid-summer onwards. When trained up supports, they take up little ground space, so can be grown successfully in compact gardens, patio containers or small greenhouses. They are closely related to courgettes, squashes and pumpkins.
This guidance applies to the crop in general. Individual varieties and local conditions can differ.
Planting information
Cucumbers are best sown indoors. For growing in a heated greenhouse, sow in mid-February to mid-March. For an unheated greenhouse, polytunnel, or large coldframe, sow in April. For growing outdoors, sow in late April. Fill 10cm pots with peat-free seed compost, water well, then sow one seed in the centre of each, 1–2cm deep, ideally on their side. Put pots in a heated propagator at 21°C or cover with a clear plastic bag and place on a warm sunny indoor windowsill. Once seedlings appear after a week or two, remove from propagator/covering and keep warm, in bright light, and watered regularly. Seeds of outdoor cucumber varieties can also be sown directly into their growing position in late May or early June. Sow up to three seeds together, 1–2cm deep. If multiple seeds germinate, remove weaker ones to leave one strong seedling. After sowing, cover with cloches or plastic-free fleece to keep soil warm and protect seedlings from slugs and snails. Plant indoor-sown or newly bought cucumber plants into their final growing site in late spring or early summer. Greenhouse cucumbers can be planted from late May into a greenhouse border or large pots once the temperature inside is consistently above 12°C; if heated, as early as late March. Outdoor cucumbers should be hardened off carefully before planting out from early June onwards, once local temperatures are reliably above 12°C. Water plants well beforehand and try not to disturb the rootball. For containers, choose a pot at least 30cm wide and deep, fill with peat-free multi-purpose compost, position one plant in the centre, firm gently, water generously, then add suitable supports. Alternatively, plant two cucumbers in a standard-sized growing bag. For planting in the ground, plant one cucumber plant into the centre of each prepared growing site, spacing them 30cm apart. Firm gently, water well, and add supports if training vertically.
Harvesting information
Cucumbers ripen from mid-summer to mid-autumn in a greenhouse, with a shorter season outdoors. Regular harvesting encourages further fruiting. Mini cucumbers should be picked at about 8cm long, small-fruited varieties at 15cm, and full-sized varieties at 20–25cm. Fruits should be uniformly green and firm, usually with a slightly rounded tip. Cut the stem cleanly with a sharp knife or secateurs, rather than pulling. Check fruits every few days. If they turn yellowish, bulbous, or soft, they are likely overripe.