Rhubarb is a cold-hardy perennial grown for its thick, tart leaf stalks, the first fruit-like harvest of the year and the basis of pies, crumbles and jams. The leaves are toxic and are never eaten; cut them off and compost them. A single planting produces for 10 years or more, so it belongs at the edge of the garden where it will not be disturbed.
Plant dormant crowns in early spring, 3 to 4 feet apart, with the buds 1 to 2 inches below the surface in rich, deeply worked soil that drains. Do not harvest in the first year and take only a few stalks in the second, so the crown builds. From the third year pull (do not cut) stalks from spring to early summer, leaving at least a third of the plant, then stop so it can store for next year. Remove flower stalks as they appear to keep the energy in the leaves. Top-dress with compost each spring.
Rhubarb needs winter chill and fades in zone 8 and warmer. Divide crowns every five to eight years, when the stalks thin, by cutting the crown into pieces with a bud each. Forced rhubarb, a crown covered with a bucket in late winter, gives pale, tender stalks weeks early. Deer leave it alone.
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.