What should I do with a bouganvillea now that the winter weather is on its way?
Bouganvilleas must be protected from the cold in the Philadelphia area. Most will go dormant and drop their leaves. Some are evergreen and can continue to grow if given sufficient light and heat. In either case, move the plant indoors, bright light is best, do not fertilize and keep soil barely moist, watering once month should be sufficient. At the end of winter you can top dress and fertilize and start watering more frequently. When there is no danger of frost, place outside in the shade and gradually move it to full sun, watering and fertilizing frequently. You can also do some light pruning before it leafs out or starts growing.
If placed in a greenhouse, they can continue to grow and even bloom. If so water more frequently and apply diluted fertilizer.