Bougainvillea is quite showy when its canopy fills with flowers, but it can be painful if planted in the wrong location. Its branches are long and thorny, and shrubs grow quite large, making it ill-suited for planting around walkways or entrances. The warmer the environment, the more rampant bougainvillea grows. Removing and killing a bougainvillea can be a long and painful process. With a little chopping and dedication in applying an herbicide to the stump, the bougainvillea should die within weeks.
Wear thick gloves such as leather, a long-sleeved shirt or sweatshirt, shoes or work boots, and long pants such as jeans, when working around the bougainvillea. The plant's branches are covered in sharp thorns and will stick you. If working close up to the plant, you may also want to wear protective eyewear in the event a branch stabs you in the eye.
Use pruning shears and loppers to trim away as many of the branches as possible, making it easier to reach the main trunk section. Rake up the branches as you go so that you do not leave any on the ground for you to step on later.
Saw down the bougainvillea's trunk as close to the ground as possible. Use a handsaw or chain saw to saw through the wood, depending upon the trunk's size. Mature bougainvillea can have large trunk sections or multiple trunks.
Paint an undiluted herbicide containing triclopyr and glyphosate (found in many commercial stump-killing herbicides) with a paintbrush over the stump. Apply the herbicide immediately to the fresh cut trunk so that the product seeps through the wound into the plant's root system, killing it.
Turn of all water to the bougainvillea, allowing the herbicide product to work, as water will dilute its strength and wash it away.
Look at the bougainvillea every two to three days, checking on any new growth sprouting from the trunk area. Trim away any new growth, and reapply the herbicide. Reapply the product one week later to make sure that the first application worked and the product is leaching to the root system and killing it.
Dig out the bougainvillea once it is dead, or allow it to disintegrate into the soil. Use a shovel to dig under the root system and loppers to cut through the roots, to lift the dead plant from its planting site.