Almost everyone loves basil. It is excellent in pesto, tomato sauce, or a simple tomato, basil and mayo sandwich. I just love the smell of basil because the smell invokes the feeling of summer, even if I am simply opening a mason jar full of basil infused olive oil.
In this hot and humid weather disease can easily set in on your plants. In my experience there are many things that kill basil during the middle of summer. Black spots can be the result of fungus', insects or parasites. Here's the thing, although you can roll up your sleeves and spray the plants with copper, or kill the bugs with whatever is recommended, I don't really bother to fight them. The plants in my opinion just need to be refreshed. So instead, this is what I do:
Select a healthy plant.
OK. So the most healthy plant you have. You can see the bottom leaves of this one has some black spot and the lowest leaves are starting to yellow, but the top of the plant is healthy and this is what I will use. (Also to prolong the life of this plant I am going to take off all infected leaves and dying leaves and prune it for better air flow. I love to crowd my plants...this obviously can backfire, but I have such a small backyard.)
2. Cut off a healthy stem.
Although the picture is a bit fuzzy because I am not the best camera person I think you can