In the midst of a hot and dry summer my basil began to look feeble. It got yellow. The leaves become somewhat thicker and dryer. I fixed the problem with a dose of acid fertilizer (see growing basil). Two weeks later the leaves are lush and green. You can see the old yellow ones under the new growth.
Oddly, I don’t really use a lot of it anymore. I am pesto-ed out. Though there was pesto on the ratatouille I had at Pastiche and it was delicious.
I grow the most lovely basil. If you want to have great basil it must be grown in a pot where it is less accessible for insects and slugs. You also need to fertilize for leaf growth and inhibit flowering. I used to grow 4 or 5 pots of it and I supplied my own restaurant with its summer needs. After I closed the restaurant I gave all my basil to a friend who had a restaurant. Enough to keep her in basil for the summer.
I once heard the Barefoot Contessa tell the television audience not to get the leaves wet, they will turn black. She doesn’t know what she’s talking about. OK, it’s not completely wrong, the leaves will turn black if the plant isn’t fully hydrated. This is why people think you shouldn’t cut it with a knife. The edges do turn black if it’s not hydrated. But you shouldn’t be using it if it’s not fully hydrated. It will look bad very quickly if you cut it. To solve this problem, you cut the ends off the stems and put it in water for a few hours. After a while you can plunge the whole thing into water. Basil absorbs water through its leaves. This should only be a problem if you’re bringing it home from the store. If you’re growing it yourself it ought be OK. Instructions follow.
Use a largish pot. 8-12 inches. I usually put about 4 or 5 plants in a pot. Once it gets growing fertilize with acid fertilizer. This is not all the organic, but sometimes things aren’t exactly right. Anyway. acid fertilizer is what was once called Miracid. Fertilizer for azaleas and pine trees. This makes it leaf out and not bloom. If you use Miraclegrow or some such thing it will bloom and then it’s A., Not as tasty. and B., Gets ragged.
Basil loves blazing sun and does very well on a balcony away from predatory insects. And believe me, there are plenty of them. If there are random holes it’s likely slugs, look around under rocks, move the pot, get it away from likely hiding areas. If entire leaves are missing, you have a caterpillar living in the dirt. Carefully dig around in the dirt and you will uncover a gray/green thing that is eating your basil. You can also, as I did this year, use diatomaceous earth. This miraculous stuff will kill anything. Organically. It feels like powder to us but to caterpillars it’s like walking on glass shards. One night and the thing will be dead. And you can rinse it off, good as new, no harm no foul. Well, except for the caterpillar.