When I worked at the garden center, if a customer bought only one herb, it was basil. Folks would ask how to harvest it and, depending on which of us was asked, the answer was usually either “pick leaves” or “cut stems.”
You don’t have to be a an either/or pruner, but thoughtful harvesting will ensure you have fresh basil all summer long.
For a few leaves on sandwiches or in salads, step out and pick a few from established plants. But when you need a good amount for a recipe, or when the plant gets about a foot tall, snip the plant above the second or third set of leaves. Two stems will grow just below the cut and your basil will produce much more basil than just picking leaves as you need them.
If this sounds simple but harsh, read this basil thread on GardenWeb to see that you can’t really do it wrong but you can do it well by keeping a few things in mind:
1. Leave 1/3 of the plant growing when you prune/harvest.
2. Let the plant recover before cutting again. Feel free to pick a few leaves (and leave enough leaves behind when you harvest to do so).
3. Harvest diligently (every four weeks or so) if you want to prevent your basil from flowering.
4. Grow multiple basil plants to harvest one each week.
Whether or not to let your kitchen basil flower is another topic entirely. I’m in the pinch-it-off camp, that is, if the plant is able to out-run my kitchen snips.
Come late fall, I let all the basil flower their hearts out. The plants are spent, the flowers look great and the little flower heads are fun to fry up in a skillet.
If I were smart, I’d harvest the seeds to get more basil.