Borage is an annual herb grown for its edible blue star-shaped flowers and cucumber-flavored leaves. It is a strong pollinator plant, attracting bees throughout summer, and is often used as a companion crop in vegetable gardens. Flowers and young leaves are edible.
It grows quickly from seed and self-sows readily, returning year after year once established. Plants have a deep taproot and resent transplanting, so direct sowing is preferred. Stems are hollow and brittle, and tall plants may flop without support or close spacing.
Powdery mildew
White or grey powdery coating on leaves — usually starting on older growth in humid conditions or when nights cool.
Improve air circulation by thinning plants. Apply neem oil or potassium bicarbonate spray at first sign. Avoid overhead watering.
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.
Borage Root Rot
Wilting despite moist soil, yellowing lower leaves, and soft brown or black roots. Plants collapse in poorly drained or overwatered conditions.
Plant in well-draining soil and avoid overwatering. Remove and discard affected plants. Do not replant borage in the same spot if rot recurs.