Answer: It's really difficult to diagnose a plant problem without actually seeing the plants, but I'll try to provide some insight. Bougainvilleas can suddenly drop leaves if the soil is kept overly wet or overly dry. They can also drop leaves if subjected to weather, especially cold winds. I'd check the drainage in the planting site - make sure water doesn't collect there. If your plants look otherwise healthy, the dropping foliage may be a natural occurance; evergreens such as bougainvillea do eventually drop their oldest leaves. You can encourage the development of new shoots and new leaves by cutting your plants back immediately after they finish flowering. Hope the above helps you troubleshoot the problem.
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