How to grow cucumbers outdoors in a raised bed in England

To grow cucumbers outdoors in England, sow an outdoor (ridge) variety indoors in late April, or straight into the bed in late May or early June, and plant out from early June once nights stay above about 12°C. Train the plants up canes or netting on the north edge of a sunny raised bed, keep them evenly watered, and pick from July to October.

This guide is for outdoor cucumbers grown upwards on a support. Sowstory plans outdoor ridge cucumbers trained up canes or netting; it does not plan trailing, unsupported cucumbers, which sprawl over a much larger area. Greenhouse cucumbers are a different crop with different care, covered only where they affect outdoor plants.

Cucumbers at a glance

Outdoor cucumbers versus greenhouse cucumbers

The RHS notes that outdoor (ridge) varieties fruit later and finish earlier than greenhouse types. The key difference is in the flowers:

• Outdoor cucumbers carry both male and female flowers. The female flowers need pollinating by insects to set fruit, so do not remove the male flowers.
• All-female greenhouse cucumbers should have any male flowers removed, or the fruit may turn bitter.

Gardeners' World adds a warning: do not grow outdoor types in a greenhouse alongside all-female types, because cross-pollination gives bitter, seedy fruit. 'Marketmore' is one example of an outdoor ridge variety.

When to sow cucumbers

For outdoor plants, the RHS suggests two routes:

1. Indoors in late April. Sow at about 21°C on a warm windowsill or in a propagator. Gardeners' World says seed needs at least 20°C and germinates in 7–10 days. Sow 1–2 cm deep; the supplier Mr Fothergill's suggests sowing seeds on their edge and potting seedlings on into 12 cm pots at the three to four leaf stage.
2. Direct in late May or early June. Sow up to three seeds per position, 1–2 cm deep, and thin to the strongest seedling.

Sowing from February is for greenhouse crops. See what to sow in April for other crops to start at the same time.

When to plant cucumbers outside in the UK

Cucumbers are tender. The RHS advises planting outdoor cucumbers out from early June, once temperatures are reliably above 12°C, after hardening them off. Sowstory plans outdoor cucumbers into the bed in June.

Timing varies across England: the south and coasts warm up earlier, while the north, inland areas, high ground and frost pockets are later. Sowstory's months are England-wide rather than adjusted to your postcode, so check your local forecast before planting. Our guide to last frost dates explains how to judge it, and what to sow in June lists what else goes into the bed that month.

Growing cucumbers in raised beds

Position and sun

Cucumbers need warmth and sun: Sowstory requires at least six hours of direct sun. Once trained up a support they are tall, so Sowstory places them on the north edge of the bed, where their shadow falls off the bed rather than across shorter crops.

Avoid tucking them tight against a wall or fence. The RHS notes that cucumbers and their relatives grown against walls and fences are often badly hit by powdery mildew, because the air there is still.

Cucumber spacing

Spacing advice varies more for cucumbers than for most crops:

Sowstory uses the wider supplier figure so a single trained plant is not crowded, which also helps air move around the leaves. In a 1.2 × 2.4 m bed, that leaves room on the north edge for other tall crops such as a couple of cordon tomatoes. The vegetable spacing chart lists the crops you might grow alongside.

Supports

The RHS grows outdoor cucumbers up a wigwam of tall bamboo canes; netting fixed to posts works too. Put the support in before planting so you do not damage the roots later, then tie the main stem in loosely as it grows and let the tendrils do the rest.

If you would rather not juggle the north edge by hand, Sowstory places trained cucumbers and other tall crops along it, tells you how many fit alongside the rest of your crops, and gives a month-by-month plan. It is coming soon to the App Store, and your first bed plan is free.

How to care for outdoor cucumbers

Pinching out

The RHS and Gardeners' World agree on the outdoor method: pinch out the growing tip once the plant has seven leaves, and pinch out any side-shoots that have not produced flowers by the time they have seven leaves.

Watering and mulching

Water at the base of the plant, ideally in the morning, and avoid wetting the leaves. A mulch at least 5 cm deep helps keep the roots moist. Steady moisture matters: the RHS says powdery mildew is favoured by roots that repeatedly dry out, and Gardeners' World says under-watering is a common cause.

Feeding

For cucumbers in containers, the RHS suggests a general liquid feed every 10–14 days, switching to a high-potash feed once flowering starts. Gardeners' World suggests a weekly high-potash feed, such as tomato food, once plants flower.

Harvesting cucumbers

Outdoor cucumbers crop from July to October. Pick them young and firm. The RHS gives these sizes:

• Mini cucumbers: about 8 cm.
• Small-fruited types: about 15 cm.
• Full-sized cucumbers: 20–25 cm.

Sowstory reserves the bed space for about 120 days from June planting, which covers the fruiting season through to autumn.

A cucumber year in England

Can you grow cucumbers in pots?

Yes. The RHS suggests a container at least 30 cm across for an outdoor cucumber, and seed suppliers such as Mr Fothergill's describe 'Marketmore' as suitable for pots and growbags. A pot still needs a cane or small frame for the plant to climb. Containers dry out much faster than a raised bed, so water them more often, and use the RHS feeding routine above: a general liquid feed every 10–14 days, switching to high-potash feed once flowering starts.

Common cucumber problems

Powdery mildew

The RHS names powdery mildew and red spider mite as the main threats. Mildew shows as a white, powdery coating on the leaves. It is favoured by dry roots combined with humid, still air. To reduce it, water regularly in dry spells, mulch, give plants their full spacing and avoid too much nitrogen. The RHS recommends against fungicides; mildew-resistant varieties are available.

Bitter or misshapen fruit

Bitter fruit outdoors can come from cross-pollination with all-female greenhouse types grown nearby (see above). Remember that outdoor plants need their male flowers and insect visitors to set fruit. Our page on cucumbers companion plants covers flowers that bring pollinators to the bed and what to keep away.

Cucumbers in the rotation

The RHS says cucumbers and their relatives can go wherever is convenient in a crop rotation, as long as they are not grown in the same spot too often. In a single bed, moving them along the north edge each year is a simple way to follow that. For more layouts, see our raised bed layout ideas, and for the usual bed-mate, our guide on how to grow tomatoes.

Sources

• RHS: How to grow cucumbers
• BBC Gardeners' World: How to grow cucumbers
• Mr Fothergill's: Cucumber 'Marketmore' seeds
• RHS: Powdery mildews
• RHS: Crop rotation
• Sowstory knowledge base, release v1.4