Bougainvillea That Has Frozen

Cold Hardiness

• Bougainvillea vines can survive a light frost, but it comes with a price. All existing flowers, bracts and foliage with wither and drop away with a couple days. Plants will rejuvenate new leaves within a month provided that no further subfreezing temperatures occur to further damage buds or remaining stems and roots. Therefore, bougainvilleas reliably survive outdoors in the United States only in U.S. Department of Agriculture plant hardiness zones 9 and warmer.

Freeze Damage

• A mature, large bougainvillea vine may be killed back to the ground when subfreezing temperatures last longer than four hours, according to Bougainvillea Growers International. Small, young, newly planted bougainvillea may be killed in the same circumstances. Once the cold penetrates into the soil and kills the roots, there is no chance for any bougainvillea plant to sprout new buds to rejuvenate the plant in spring.

Container Insight

• Plants growing in the ground are better insulated from subfreezing temperatures. Vines in above-ground containers live in small volumes of soil that can retain heat. The pot's soil can cool down and match the air temperature. In the ground, the topsoil may remain 10 to 20 degrees Fahrenheit warmer, protecting the roots. On nights when frosts or freezes are forecast, relocate containers indoors temporarily to prevent root damage from the cold. Alternatively, wrap the containers with blankets to insulate the soil from cold.

After the Freeze

• Do not rush to prune the frozen bougainvillea plant. Continue with your usual watering schedule. Chances are the plant will sustain considerable branch dieback, but the lower trunk and roots may remain alive. Pruning too early may remove living tissues or expose lower parts of the plant to more cold if another frost or freeze is possible that winter. Wait until mid to late spring, after the plant naturally begins to reveal any new leafy buds and shoots, to prune. If no new growth returns by early June, that winter freeze proved too cold. Do not overwater or being to fertilize until the plant shows signs of new growth.