When the basil plants get tall, it's time to make pesto (or dry it, but that's another story). These plants started out as living basil in the grocery store several months ago. The grocery store can be the source of many growable items (that's also another story). These have been growing inside hydroponically all winter. The plan was to start these from cuttings taken from the basil growing in the yard last season but the cold killed those plants before they could be taken. So the grocery store became the source.
These plants have already undergone multiple cut backs. Prune the higher stems and put in water and they usually root. And then there are even more basil plants to provide even more basil.
This recipe is from the New York Times. Suggests that the pesto can be made with pine nuts or walnuts. I disagree. The walnuts do not work, at least for us. Fortunately, the basil may be frozen in olive oil for future incorporation into pesto, because these plants keep growing and we're not always ready for pesto when they need to be harvested.