Prune your basil plant before it gets too tall, as this decreases its girth, slows leaf production, and reduces air flow to the bottom of the plant, making it leggy and weak.
Start pruning once your basil plant grows 6 to 8 inches tall to encourage it to produce leaves throughout rather than just on the top, thereby developing a healthy, bushier shape.
When removing basil leaves, always start picking them from the top of the plant rather than from the bottom; otherwise, leaf growth can decrease, and the plant can get leggy.
Picking the top leaves stops your basil getting too tall and encourages the top to fill out. If you cut whole stems, do so from just above two new ones so new growth soon occurs.
Regularly pruning basil — every two to three weeks during the growing season — prevents it from getting leggy, stimulates leaf production, and grows better-tasting leaves.
You can also prune in between scheduled sessions if it gets too tall or starts flowering. If an individual branch produces six or more leaves, prune it back to its first set.