Plant bougainvillea when there's no danger of frost.
Plant them in full sun; they need at least five hours a day of direct sunlight.
Measure the depth of the bougainvillea's original nursery container. Dig the bed for the plants to that measurement, plus 3 inches. If the soil in the flower bed is heavy or clay, combine it with equal parts of sand and compost. Mix and spread evenly on the soil.
Dig a hole for your bougainvillea that's 2 inches deeper than its container.
With the scissors, cut down one side of the container, across the bottom and up the other side.
Set the plant in the hole with the container still on it. Very gently pull the halves of the container off the root ball. Discard the pieces of container.
Carefully push dirt under and around the bougainvillea until the stems above the roots are level with the adjacent soil. Handle the roots very carefully; they are fragile, easily damaged and can affect how well your bougainvillea does for the rest of its life.
Water the plant well, getting all of the roots thoroughly wet. Let it dry completely before you water it again; you can wait until it starts to wilt a bit before you water again. Test the soil for dampness by sticking your fingers into the dirt by the bougainvillea's roots.
When the growing season begins, fertilize the plant with an iron-heavy fertilizer such as a 6-8-10 mixture, mixed and applied according to the package instructions. Feed the plant according to the schedule on the fertilizer as long as it's blooming. When blooming slows, cut back to fertilizing it half as often as during the growing season.
Prune the bougainvillea at the beginning of summer. You can cut the plants back by as much as a third if they are getting unruly. Encourage growth in the interior of the bougainvillea by cutting the stems there, so they will branch and fill in. Throughout the growing season, continue to prune it to develop a tight, compact shape.
As the plant puts out new stems, gently pinch ½ inch off the tips of all the new growth. This will make the stems branch and fill in with new foliage and flowers.