The bougainvillea needs full sun and high temperatures for producing flowers and for that reason it should be placed outside in a sunny place during the growing season. Bougainvillea flower continuously from spring to autumn in warm-hot regions. As bonsai, the flowers should be removed when they fade to encourage a second blooming period.
During the winter months, the plant should be kept on the dry side but must be watered copiously as soon as the buds start swelling and when the plant is in bloom.
Water the bougainvillea thoroughly when the soil gets dry, but avoid constant soil wetness which will lead to root rot, fungal problems, insect susceptibility, and death. The species prefers a pH value of 6 to 6.5, so avoid using highly calcareous water.
Apply solid organic fertilizer once a month or use a liquid fertilizer every week during the growing season and every two weeks in winter.
Pruning and wiring
Cut the shoots after flowering, leaving two leaves on each, and prune twigs and branches in autumn or winter. The bougainvillea can bud from old wood after hard pruning. If you want the tree to flower, don't pinch and trim it too much in summer. Use cut paste on larger cut wounds. Those heal over slowly. Wiring is possible on young shoots and twigs but older branches are very stiff and break easily. Beware of the thorns when you are wiring bougainvilleas.
Repot smaller bougainvilleas every two or three years. Larger specimens can be repotted every three to five years. A well-draining standard soil mix is fine for this species. The roots of the bougainvillea are yellow, thin, and delicate. Take good care not to tear off the roots when you remove the rootball from the pot! Untangle the roots tenderly and don't use the root rake with force. Root pruning is tolerated well.
The bougainvillea can be propagated from cuttings. Best results are achieved in spring and summer with semi-hardwood cuttings or root cuttings. Air-layering is also possible.
Pests and diseases
The bougainvillea tends to be pest resistant as long as is kept healthy and free from wet soil conditions or lack of light. Weak plants can be attacked by powdery mildew, aphids, scale, mealybug, whitefly, or caterpillars. In that case, use specific pesticides and try to improve the conditions for your tree. When the flowers wilt, cut them off to prevent rot.