Answer: It sounds as though your basil is ready to bolt (produce flowers). You want to avoid that for as long as possible. The best way to keep your plants bushy and to keep it from flowering is to pinch out the growing tips every 10-14 days. Just pinch the very tips of each stem and the plant will produce two new stems. Wait until the new stems produce 4-5 leaves and pinch the tips of each of those stems. This will allow you to harvest some of the leaves every week. If you don't have an immediate need for the leaves you can spread them out and allow them to dry, then store them in your spice cabinet for use later in the year.
Best wishes with your basil!
Q&A Library Searching Tips