Celery is slow to germinate so grow in module trays and then transplant. Sow in March for planting out in May (when they have four to six true leaves). Harden off before planting out. Self-blanching celery is typically planted in blocks rather than in rows, so the plants shade each other from light (thereby improving the blanching process).
Blanching celery makes the stems go white and more tender. Even “self-blanching” varieties benefit from blanching – homemade collars can be made from strips of black plastic wrapped around the plant. Traditional trench celery is blanched by “earthing up” the trench in which it was sown. Water celery well in dry weather – it’s a thirsty plant and if the soil dries out the stems won’t swell. If leaves go yellow, apply an organic feed (e.g. nettle or comfrey tea).
Celery will be ready in approx 40 weeks – usually August-Oct. Lift as required but finish harvesting when frosts arrive. Use a fork to gently lift the plant, roots and all. A head of celery will keep in the fridge for up to 3 days.