Move the bougainvillea in spring, before the weather warms. Plants transplant most successfully in cool, moist conditions. Hot, dry conditions lead to root drying and plant death.
Find a new site for the bougainvillea. Choose a site with six to eight hours of full sun every day, quick drainage, good air movement and a fence, trellis or wall for climbing.
Digging into the top 12 inches of soil in the new site loosens and aerates it. Turn 3 to 4 inches of organic compost into the natural soil to build a loose, fine consistency and add nutrition. Bougainvilleas have shallow, fine root systems and fail in thick or heavy soil.
Prune the bougainvillea if it's large. The plants regenerate quickly with 18- to 20-inch stems. It transplants easier with less foliage.
Dig around the bougainvillea's root ball and lift it from the soil. De not break or damage the fine roots. Move the entire root ball for best success.
Plant the bougainvillea in the new site in a hole deep and wide enough to contain the root ball. Watering the roots with 1/2 gallon of water settles the soil.