Q. How do I overwinter my agapanthus?
To overwinter your agapanthus, you first need to determine whether it is evergreen or deciduous.
If your agapanthus keeps its leaves after summer, it is probably an evergreen. If the leaves die back naturally, it is deciduous. Cooler temperatures and less light cause the process of dormancy. Leaving it outdoors long enough to see if it goes into dormancy is helpful.
Evergreens should be kept under cool greenhouse or conservatory room conditions, meaning a very bright location with temperatures in the 55-60°F range. In a basement, you could experiment with using ordinary fluorescent bulbs close to the plants, running about 16 hours or so each day. During the winter, water lightly.
Deciduous agapanthus should be kept cooler, approximately 40-50°F, and allowed to rest for the winter. These plants do well in an unheated, cool basement. Since they have no active foliage, they don't need special light. The soil should be kept just barely moist, meaning not allowed to go dry as a bone, until they resume active growth in the spring.
If your didn't produce flowers, it is probably because it is young. Water regularly but sparingly throughout the growing season and feed two a month with a high-potassium fertilizer like tomato feed.
Here are some other reasons for an agapanthus not flowering:
- It may not have had at least 6-plus hours of direct sun, or enough nutrition.
- Agapanthus benefit from an annual feeding in spring and organic mulch in the fall.
- Although they like to be potbound to flower well, eventually they will flower a lot less or not at all. This is the signal that it's time to divide in spring. This is a major job, due to agapanthus's tangled, fleshy, heavy root system.
Again how old is it? We have 12 plants here at NYBG, a mix of deciduous and evergreen. There are many varieties available in commerce. Do you have the original name of yours?
Whether grown in a container or in the ground, all Agapanthus should be divided every four years or so—deciduous types in March, just before they start growing, and evergreen forms immediately after flowering.
For tips on a variety of gardening topics, see our Plant Information Guides.
- Courtesy of NYBG Plant Information Service