[header] How to propagate bougainvillea [title] Cut a mature stem to a length of 6-8 inches (15-20 cm). [step] Use a pair of sharp pruning shears to snip the lower end of the stem at a slight angle. Only take healthy cuttings that do not have signs of disease of infestation. 
Cutting the stem at an angle increases its surface area, allowing it to take up more moisture and nutrients from the planting soil. [substeps] Wear gardening gloves and eye protection when you take a cutting.