Measure the herb plants to be trimmed with the ruler. Basil and other herbs in the garden need to be 6 inches or taller before the first trim. Only established herbs should be trimmed.
Use scissors to cut 2 inch stems from the top of the herb plant. Up to 1/3 of the plants leaves may be trimmed at one time.
Repeat step 2 every two to four weeks. According to the West Virginia University Extension Service, basil should be trimmed often and kept compact as lush growth may reduce the herb's flavor.