Answer: Many subtropicals will be damaged by frost but are killed only by severe freezes. Bougainvillea bloom freely in the summer and into the fall, but the tops will be killed in the winter. Wait until new growth begins in April before you cut back the frozen parts. 'Barbara Karst' and 'San Diego Red' are the most vigorous Bougainvillea, so they recover quickly and are highly recommended. Plant on a south-facing wall for winter sun, under an overhang to trap heat. Cloth and paper provide the best insulating qualities to hold in heat. If sheets are not available, consider purchasing frost blankets sold in garden centers and nurseries. These are made of non-woven polypropylene that is light weight and can be left on plants for several days without causing them harm.
Newspaper also makes and excellent frost blanket material. The newspaper covering should be several sheets thick to maximize cold protection. When frost covers of any type are used, it?s important that they be secured properly. Cold snaps are usually accompanied by windy conditions, especially the first night of a cold snap. If plant covers are not secured properly, warmth will escape from under the cover. Cold air will also be forced under the cover on windy nights.
Hope this information is helpful!
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