Plan for steady moisture
Celery can be grown in an allotment, but it is less forgiving than many crops because it needs fertile soil that remains evenly moist. A bed that dries out repeatedly can produce stringy, hollow or bitter stems. Choose a sunny or lightly shaded site with reliable access to water. Add mature compost before planting and avoid a position that is waterlogged in winter.
Modern self-blanching varieties are the simplest choice for most home growers. Traditional trench celery needs more space and gradual earthing up to pale the stems. Check the seed packet so you know which type you have; blanching methods are not interchangeable.
Sow in warmth and plant out after cold weather
Sow seed under cover from February to April. Celery seed is small and needs light, so press it onto moist compost and cover only lightly. Keep it warm, around 18–21°C, and do not allow the surface to dry. Germination can be slow. Prick seedlings out carefully once they are large enough to handle and grow them on in good light.
Harden plants off and plant out from May to June once cold weather has eased. Space plants roughly 25–30 cm apart, with rows wide enough to weed and water easily. Water in well and protect small plants from slugs. In a small plot, a large container can work if it holds moisture and has free drainage.
Water, mulch and feed through summer
Water deeply and regularly, especially during warm spells and while stems are expanding. Apply water at the soil rather than splashing foliage. Mulch once the soil is already moist to slow evaporation, keeping material away from the crown. A light balanced feed can help on poor ground, but excessive nitrogen may give soft growth.
For self-blanching types, follow the packet and leave stems exposed to light. For traditional trench types, gradually draw soil around stems as they grow, keeping the foliage clear and avoiding soil in the heart. Paper collars or boards may also be used for the variety, but remove them if they trap dampness or pests.
Troubleshoot and harvest
If plants bolt, check for cold stress when young, dry soil or transplant shock. Keep a consistent water supply and remove flower stems promptly, although a bolting plant will not return to normal cropping. Slugs, aphids and leaf spot can affect crops; use clean spacing, inspect regularly and remove badly damaged leaves.
Harvest outside stems as needed from late summer, or cut the whole plant when it reaches a useful size. Use clean tools and chill stems promptly. Celery is best harvested before hard frost damages it; in colder regions, lift late plants rather than expecting them to stand through severe freezes.