It’s sadly ironic that as soon as summer weather comes, just when your homegrown cilantro would work so perfectly for a nice fresh salsa or grilled skirt steak—it dies. This particular quirk of the leafy herb, to die as the days lengthen and grow hot, make it difficult to plan for platters of fish tacos, but there is a method to insure that you can have fresh cilantro all summer.
Cilantro is a true annual plant (annuals grow from a seed, flower, set seed, and die all in the same year) triggered to flower by the longer days and warmer temperatures of summer. The leaves are used in many cuisines. The seeds are the source of the spice coriander. Because the leaves are best used fresh (they lose aroma once frozen or dried) a reliable source of fresh cilantro through the summer is quite handy.
To ensure yourself fresh cilantro through the season, buy several packets of seeds. Fill a pot with good potting soil and sprinkle the seeds across the soil. A pot at least 8-10” will keep soil cooler than a small pot, so don’t go too small. Try to get the seeds a few inches apart, but don’t get too obsessive about it (you won’t use all of the seeds yet). Cover seeds with ¼-½” of soil and water well.
Place the pot in an area that gets about 6 hours of sun, preferably in the morning and late afternoon. You’re looking for some shade during the hottest part of the day to keep the plants as cool as possible. Don’t let the soil dry out completely.
As soon as the seeds sprout, get another container and sow another pot full of seeds. You can start harvesting from your first container when the cilantro plants are big enough to be cut. Cut from a different section of the pot each time you need some, eventually working around to the first area you harvested. Depending on how much cilantro you use it should regrow a few times before it gives up. By then, pot #2 should be ready to start cutting. Replant pot #1 and start again.
You may be such a cilantro fan that you need 3 or more pots going, or perhaps one will suffice if you’re just a garnisher (you can plant half of the container, then the other half instead of using two pots). But this method of succession sowing should keep you in cilantro during most of the summer months.
Bonus tip: This will work for dill (another annual herb) as well.