Cucumbers

Home-grown cucumbers taste fabulous and can be grown in a greenhouse or in a warm sheltered spot outdoors, depending on the variety. Seeds can be sown indoors or outside too, from spring to early summer, or you can buy young plants from garden centres. 

Jobs to do now

  • Sow seeds indoors
  • Pot up

Month by month

Sow

Sow

Indoors

Sow cucumber seeds on their side, 1–2cm (½–¾in) deep, in small pots. Keep them at 21°C (70°F) in a heated propagator or on a warm sunny indoor windowsill.

Sow from mid-February to mid-March if you’ll be growing them in a heated greenhouse, or in April if you have an unheated greenhouse. If you’re going to plant them outdoors, sow in late April.

Outdoors

Outdoor varieties can be sown directly in their growing site in late May or early June. Sow seeds 1–2cm (½–¾in) deep.

Cover the ground with fleece, a cloche or glass jar after sowing. This method can work well in milder southern areas and in warm summers.

Young plants are also available from garden centres in spring.

Grow

Grow

Growing in a greenhouse

Make sure your cucumber plants don’t get chilled – they must be kept above 12–15°C (53–59°F).

Transfer young plants to 25cm (10in) pots of good-quality potting compost in late March (in a heated greenhouse) or late May (in an unheated greenhouse). You can also use growing bags, but plants will need to be carefully watered and looked after. Alternatively, plant into greenhouse borders, enriched with plenty of garden compost.

Water little and often to keep the potting compost or soil evenly moist. Raise the humidity in hot weather by watering the greenhouse floor, so the moisture evaporates.

Feed every 10–14 days with a balanced liquid fertiliser.

Train the main stem up a vertical wire or cane. Pinch out the growing point when it reaches the greenhouse roof. Pinch out the tips of sideshoots two leaves beyond a female flower (which has a tiny fruit behind it). Pinch out the tips of flowerless sideshoots once they reach 60cm (2ft) long.

Growing outdoors

Plant out young plants or sow seeds outdoors in early June, ideally under fleece or cloches.

Choose a warm, sheltered, sunny spot with fertile soil. Prepare the ground by digging in up to two bucketfuls of well-rotted organic matter, such as garden compost, then rake in 100g per square metre (3½oz per square yard) of general purpose fertiliser.

When plants have developed seven leaves, pinch out the growing tip. The developing sideshoots can be left to trail over the ground or trained up stout netting. Pinch out the tips of flowerless sideshoots after seven leaves.
 
Don’t remove the male flowers, and keep the soil constantly moist by watering around the plant, not over it. 

Harvesting

Harvesting

Cucumbers ripen from mid-summer to mid-autumn in a greenhouse, with a shorter season outdoors depending on the weather.

Fruit size varies according to the variety, so check your seed packet. In general, smaller-fruited varieties are best at about 10cm (4in) long and full-sized varieties at about 15–20cm (6–8in). The fruits should be uniformly green and firm, usually with a slightly rounded tip. Fruits can grow rapidly, so check them regularly to get them at their best. If they turn yellowish, bulbous or soft, they may be over ripe. 

Cut the stem cleanly with a sharp knife or secateurs. Regular harvesting encourages further fruiting.

Recommended Varieties

Common problems

Whitefly
Whitefly

Small white flies suck sap and excrete sticky ‘honeydew’ over the plant, encouraging the growth of sooty mould.

Remedy

Use biological control or sticky traps in the greenhouse.

Cucumber mosaic virus
Cucumber mosaic virus

Plants and leaves are stunted and deformed, and leaves show distinctive yellow mosaic patterning. Flowering is reduced or non-existent, while any fruit that do appear are small, pitted, hard and inedible.

Remedy

The disease is spread from plant to plant by sap-sucking aphids, so take any necessary measures to control them. Infected plants should be destroyed – wash your hands after touching infected material to avoid contaminating healthy plants.

Powdery Mildew
Powdery Mildew

Appears as a white powdery deposit over the leaf surface and leaves become stunted and shrivel.

Remedy

Keep the soil moist and grow in cooler locations.

Recipes

Nigel Slater’s radish, mint and feta salad has plenty of cucumber to add freshness and crunch.

Get involved

The Royal Horticultural Society is the UK’s leading gardening charity. We aim to enrich everyone’s life through plants, and make the UK a greener and more beautiful place.