Bougainvillea Temperature Tolerance: From Heat to Frost

Bougainvillea is a tropical vine known for its vibrant displays of color, which come from paper-like structures called bracts. Native to South America, this sun-loving plant’s health and appearance depend heavily on temperature. Understanding its needs for warmth and its limitations with cold is important for cultivation.

Ideal Growing Temperatures

For lush growth and bract formation, bougainvillea thrives when daytime temperatures are between 75 and 95 degrees Fahrenheit (24-35°C). This warmth fuels the development and energy required for profuse blooming. Nighttime temperatures are also important and, for best results, should remain at or above 65°F (18°C). Consistent warmth signals the plant to continue its growth and produce colorful bracts.

Cold Tolerance and Frost Damage

Bougainvillea flourishes in heat but is vulnerable to cold. An established plant may tolerate a brief dip to around 30°F (-1°C), but this is its outer limit. A hard frost or prolonged period below freezing can cause significant damage and potentially kill the plant, with young bougainvilleas being especially susceptible.

Signs of cold damage include wilting leaves that turn brown or black and stems that blacken from the tips. This sensitivity is why bougainvillea is recommended for USDA Hardiness Zones 9 through 11, where winter freezes are rare. Gardeners outside these zones must provide winter protection.

Protecting Bougainvillea in Winter

For bougainvillea planted in the ground, apply a thick layer of mulch around the base to insulate the root system. Before a predicted frost, cover the plant with a frost cloth or blanket. Use stakes to create a frame that prevents the cover from touching the foliage, as this can trap moisture and increase damage.

Container-grown bougainvillea is easier to protect by moving the pot indoors before the first frost. A garage, shed, or basement is a good overwintering location. If brought into a living area, place it near a sunny window for adequate light. During this indoor period, reduce watering significantly, allowing the soil to dry out more between waterings.

Surviving High Heat

While bougainvillea loves heat, it can show stress in temperatures consistently above 100°F (38°C). Symptoms include wilting during the hottest part of the day, leaf scorch where the edges appear burnt, or a temporary halt in blooming.

To help a bougainvillea cope with a heatwave, provide consistent and deep watering, which is especially important for potted specimens. Applying a layer of organic mulch over the soil surface helps retain moisture and keeps the root zone cooler.