Annual geranium is a tender perennial grown as an annual in upstate New York. It produces rounded clusters of red, pink, white, or salmon flowers above scalloped leaves from late spring until frost. It is reliable in containers, window boxes, and beds, and tolerates heat better than many bedding plants.
It blooms continuously if spent flower heads are removed. Plants are not frost hardy and must be set out after the last spring frost. They prefer to dry slightly between waterings; constant wet soil causes stem and root rot. Plants can be overwintered indoors as cuttings or dormant stock.
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.
Damping Off
Seedlings collapse at the soil line with thin, water-soaked stems; seeds may fail to emerge or rot before sprouting.
Sow in well-draining mix, avoid overwatering, and ensure good airflow. Remove affected seedlings and let the surface dry between waterings.
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.
Bacterial Blight of Geranium
Small water-soaked or brown spots with yellow halos on leaves, V-shaped yellow wedges along leaf margins, wilting, and blackened stems.
Remove and destroy infected plants; avoid overhead watering and handling wet foliage. Use clean tools and disease-free cuttings, and space plants for airflow. No chemical cure once infected.