Rhubarb is a cold-hardy perennial grown for its thick, tart leaf stalks, used in cooking. The leaves are toxic and should never be eaten. A single planting produces for 10 or more years, making it a long-term fixture in the garden.
Plant dormant crowns in early spring, setting the buds 1–2 inches below the soil surface. Do not harvest in the first year; take only a few stalks in year two to let the plant establish. Remove flower stalks as they appear to keep energy in the leaves and roots. Divide crowns every 5–8 years when stalks thin.
Crown Rot
Lower leaves yellow and wilt; the base of the rosette turns brown and soft, sometimes with white fungal threads at the soil line. Plants collapse in wet conditions.
Remove and destroy affected plants. Improve drainage and avoid overhead watering. Do not mulch directly against the crown. Space plants for airflow and avoid replanting in the same wet spot.
Botrytis (grey mould)
Grey fuzzy mould on petals and stems, worst in cool wet conditions.
Remove affected parts immediately. Improve air circulation. Avoid overhead watering. Apply copper fungicide if severe.
Fungal leaf spot
Brown or purplish spots on the leaves, often ringed with a yellow halo, that spread and merge in warm, humid, or wet weather; heavily spotted leaves yellow and drop early.
Pick off spotted leaves and clear fallen debris to remove overwintering spores. Improve air circulation by thinning, and water at the base so foliage dries quickly. If it persists, apply a copper- or sulfur-based fungicide at the first sign.