In a greenhouse, humidity can be raised in hot weather by dampening (wetting) the floor, overhead watering, or misting. However, high humidity can cause fungal problems, in which case open vents to improve ventilation.

moisture during bright periods to encourage bud break
Repot if necessary in early spring with clay-based compost such as John Innes 3
If packaged, place outdoors in full sun, preferably 18-21°C (65-70°F) at night, a few degrees warmer during the day
When plants are growing vigorously around mid-April, water freely and feed weekly with a high-nitrogen liquid feed
When the bracts show color, change to a high-potassium feed and move the plants to cooler conditions (if possible to 10°C (50°F)) with good ventilation and protection from direct sunlight. This encourages the bracts to mature and remain longer on the plant. Cooler conditions can cause the leaves to hang for several days so water less often until the plant adjusts
Once bracts have dropped, resume high nitrogen application to encourage a second flush of bracts

Autumn and winter
When flowering ends, usually in September, reduce watering frequency, allowing the plant to become drier between waterings and stop feeding
From November, water occasionally but thoroughly
Maintain a minimum nighttime temperature of 10°C (50°F). Bougainvillea can be stored above freezing provided the compost is kept relatively dry but they will lose leaves
Pruning and training
Bougainvillea requires a trellis or pillar for support and can be trained as a standard and pruned with spurs to limit size. They bloom on the current season’s growth so prune in late winter or early spring, just before growth begins.

Early in the season, bend and tie in young vigorous growing leaves to control vigor and stimulate bract formation
After the bracts have fallen, this long growth is halved to encourage a second flush of bracts in late summer