Diggin In: How to overwinter bougainvillea
Q: My $17 bougainvillea exceeded all expectations this summer and is a mass of gorgeous blooms and bracts. How can I overwinter it inside?
A: Bougainvillea is native to parts of South America that experience a distinct dry, cool season and a warm, rainy season. The plants typically bloom most profusely at the start of the rainy season.
Emulate those conditions to keep your bougainvillea healthy. When you bring it indoors, place it in a cool location where it gets ample sunlight. Be careful not to over-water it. Bougainvillea is very drought-tolerant, and the soil should be allowed to dry a bit between watering. All or most of the leaves may drop, depending on your growing conditions. If that happens, you no longer need to keep it in a sunny location, and you can move it to a garage or basement that is cool but protected from freezing.
Move your bougainvillea back outdoors in early May and repot it. Give it a light application of fertilizer every month while it is outdoors, or use slow-release fertilizer granules at the lowest rate recommended. Excess fertilizer results in rampant growth of the vines at the expense of flowers.
Scott Aker is a horticulturist at the U.S. National Arboretum.
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