Broccoli raab (rapini) is a fast-maturing Italian green grown for its tender florets, leaves, and stems rather than a tight head. It bolts quickly — that's the point — producing small broccoli-like florets that, harvested before the flowers open, are nutty, slightly bitter, and excellent roasted or sautéed. Sow in early spring for a cool-season harvest, then again in late August for a fall crop as temperatures drop.
Clubroot
Swollen, distorted roots; wilting in midday heat; stunted growth and yellowing foliage. Plants recover poorly even with watering.
Remove and destroy infected plants with roots. Raise soil pH toward 7.2 with lime. Improve drainage and rotate out of brassicas for several years.
Flea Beetle
Small round shot-holes scattered across leaves; tiny dark beetles that jump when disturbed. Heavy feeding stunts young plants.
Use floating row covers on seedlings. Remove crop debris and weeds that harbor beetles. Apply kaolin clay or spinosad if damage is severe.
Downy mildew
Yellowing on top of leaves with grey-purple fuzz underneath. Spreads rapidly in humid conditions.
Remove affected leaves. Improve air circulation. Avoid overhead watering. Copper spray as preventive.
White Rust
Raised white to cream-colored pustules on leaf undersides, with yellow blotches on upper surfaces. Infected tissue may swell or distort.
Remove and destroy infected leaves. Improve air circulation and avoid overhead watering. Rotate brassicas and avoid planting in previously infected soil.
Cabbage Worm
Ragged holes in leaves and green velvety caterpillars on undersides; dark green frass collects in leaf crevices and head.
Handpick caterpillars and eggs. Apply Bacillus thuringiensis (Bt) weekly during egg-laying. Use floating row cover to exclude white cabbage moths.
Aphids
Clusters of small soft insects on new growth and flower buds.
Knock off with a strong jet of water. Ladybirds and lacewings are natural predators. Insecticidal soap as last resort.