Verbascum is one of the most dramatic tall verticals in the cutting garden — a massive woolly silver-white rosette in the first year, followed by towering yellow flower spikes up to eight feet tall in the second. It is biennial and borderline short-lived perennial, but self-seeds reliably. The architectural quality is extraordinary: nothing else provides the same combination of scale and silvery texture.
As a cut flower, the flowering spike works well in large arrangements where height and vertical drama are needed. Cut when the lower third of the spike is open. The dried seed stalks, left silver and skeletal through winter, are structural and beautiful.
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.
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.
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.