Q. What is the recommended procedure for overwintering annual geranium plants?
A. There are several procedures gardeners use to overwinter unusual or hand-to-find Pelargonium cultivars. Not all methods have the same success rate. During winter, Pelargonium plants appreciate cool conditions with a 10-degree difference in night temperatures.
- The most reliable method consists of taking stem cuttings in spring or late summer. Cut a 3- to 6-inch piece from a non-flowering stem. Remove all lower leaves from the stem cutting and place it in a pre-dampened soilless mix. Do not use rooting hormone with Pelargonium cuttings. Place in a sunny window. Water only when soilless mix is dry. As plant begins to grow, pinch back growing tips to encourage bushy habit. Fertilize with a dilute balanced mix in early spring. Take plants outdoors after all danger of frost has passed.
- Dig up the entire plant before the first fall frost. Check thoroughly for any signs of insects or disease since it makes no sense to bring problem plants into the house. Shake off loose soil and repot the plant in a fast-draining soilless mix. Cut back the plant to 6 to 8 inches. Water thoroughly and then let plant dry slightly before watering again. Place in a sunny window all winter. Pinch straggly growth to keep a compact habit. With reduced watering in winter, eliminate or greatly reduce fertilizer unless the plant is producing flowers. In that case, fertilize once a month with a dilute balanced mix. Take the plant outside when weather is consistently warm in spring.