Bougainvillea plants, native to Brazil, have become popular in the U.S. as warm-season annuals in USDA hardiness zones 9 and up. Bougainvillea are tropical to semi-tropical flowering vines with spectacular flowerlike bracts and colourful leaves it produces all season long. Bougainvillea grow well in pots and can be planted in the ground in warm climates, but the vine is not at all cold-hardy and will die when confronted with temperatures near freezing. Bougainvillea are heavy feeders that need consistent levels of nutrients applied in slow-release applications. Bougainvillea can wilt due to extremes of water, temperature and fertiliser.
Pot the plant in a container that just contains the root ball. Bougainvillea bloom best in a confined area. Make a potting mix that comprises very little actual soil as it will dry out too quickly. The potting mix also needs to be free draining. Combine one part potting mix with two parts compost and one part sand. This provides the drainage and nutrient combination that will allow the bougainvillea to thrive.
Remove the plant from the original pot. Fill the new pot halfway with the planting mix you made. Put your bougainvillea into the pot and fill the rest of the way with your planting mix. Disturb the roots as little as possible. Expect some wilting due to transplant shock.
Water the bougainvillea soil when it feels dry. Too much watering can cause wilt, as can too little. Do not put the pot on a saucer, as this keeps the roots too wet. Water until the pot leaks moisture and then allow to dry out until the next watering. Check the moisture level by tipping the pot and feeling the drip holes on the bottom. If the soil feels wet, allow another couple of days to go by before watering. If it is barely damp, it is time to water.
Fertilise the plant after a month. Do not fertilise sooner, as the roots will not have had time to establish, and the plant will be tender and can burn. Too much fertiliser causes the plant to wilt but too little will cause the plant to slow its growth and stop producing flowers. Fertilise monthly with balanced fertiliser (such as 5-5-5), that provides a slow release of nutrients. Follow the manufacturer's instructions for the proper amount to apply and lightly dig the granules into the soil around the base of the plant.
Keep the bougainvillea in full sun. If it is in shady or partially shady conditions, it will become limp. Bougainvillea should be moved indoors when the temperatures drop. Grow the plant where night temperatures are 18.3 degrees Celsius and day temperatures are between 23.9 and 35 degrees Celsius. Cool temperatures (below 0-1.111 degrees Celsius) will cause the plant to wilt.