Answer: Bougainvilleas bloom on new wood, and they bloom on a 5-6 weeks cycle. Prune them back after each flush of flowers and they will remain bushy and bright. If you have a bright, sunny location indoors it might overwinter for you. Any well-drained potting soil will do. Use a pot that is at least 18 inches deep and wide. Don't overwater or over fertilize; allow the soil to dry out between waterings and fertilize no more than once a month. If you can overwinter it, leaving it in a pot might be best, as constantly transplanting it will be a shock to its root system.
I'm not sure that a garage is the best place for your Bougainvillea. To remain alive, it needs at least 4 hours of sunshine a day. If you can provide supplemental lighting, it just might be happy in the garage.
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