Bougainvillea blooming slows down or discontinues when the weather turns cool because it needs to rest before the show starts again.
Bougainvillea can survive occasional below-freezing night temperatures as long as they aren’t consecutive. A few winters ago here in Tucson, we had 4 or 5 nights below 32F but they weren’t in a row.
Large bougainvilleas are hard to cover. The best thing you can do is protect the roots. Apply at least a 3 inch layer of mulch (hay, leaves, compost, etc) around the base of the plant covering the area where the roots grow
Even though it looks dead, it may not be. The outer growth may have been hit but the inner growth might be just fine. The same applies to the tip growth. Do a scratch test on a branch and look for green under the bark.
Here in Tucson (with colder evening temps) I wait until mid to end of March to do any extensive pruning. Have patience – you don’t want to prune your bougainvillea and then have another freeze hit!
Winter care for potted bougainvillea plants is basically the same for those growing in the ground. The only difference is that you’ll probably have to water bougainvillea container plants more often.
Want more tips on houseplant care & gardening?