Answer: Bougainvilleas usually begin to show damage at 35F. Normally, just the foliage is affected; at temperatures hovering around freezing, the stems can die; a hard freeze can kill the tops of the plants, but the roots normally survive so the plants recover in the spring and produce new tops. Since this winter was exceptionally cold throughout the west coast, I think you'd be safe in planting bougainvilleas in your garden. If the tops are killed by winter cold, cut the plants back to within a few inches of the ground and they should come back the following spring.
Best wishes with your landscape!
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