The first step to preventing bolting is to understand what causes it. Bolting, or going to seed, is a natural part of the plant's life cycle. Some plants have longer life cycles than others. Arugula, lettuce, cilantro and dill all have relatively short life cycles, so they will try to produce seed within 8 to 10 weeks of being planted. It is an inevitable part of the plant life cycle but can be postponed with good management. It can also be caused by shock during transplanting, by too much or too little water, and around the solstice when the days start getting shorter. Transplant shock can be minimized by careful hardening off and transplanting in late afternoon when the plants will not be exposed to intense midday heat. Water carefully and time your plantings so that a fresh generation is coming along before the previous generation goes to seed. Here is a helpful schedule to help you maximize the harvest:
Cilantro - plant every 3 weeks from late April to mid August. These are very cold tolerant and can be grown early and late to extend the season. If you are very eager to have cilantro for salsa, then make sure to plant some in early July so that it is ready to eat at the same time as your tomatoes are ripe. The flowers of cilantro are edible and are a lovely addition to salads and salsas.
Dill - like cilantro, is very cold tolerant and can be grown early and late in the season. This self seeds willingly, so you can always allow a patch to flower and drop its seeds giving you a perpetual patch. The flowers of dill are tasty in pickles and marinades.
Lettuce - lettuce can be grown at the baby leaf stage or the full head stage. Please refer to our lettuce post to learn more about the timing of lettuce. It should be planted every week or two if you eat lots of salads and want fresh, non-bitter leaves on your plate. It can be planted from seeds or from plants. If you prefer the texture and flavor of full heads of lettuce, then transplant individual plants every 10" - about 4 to 8 transplants a week is plenty. If you prefer cut lettuce leaves, then use seeds, and sprinkle them in a row, about 2 or 3 seeds per inch. Cut lettuce leaves can grow back and provide you with a second harvest, but the quality goes down each time and the bitterness increases. It is best to replant a fresh row of seeds every couple of weeks.
Arugula - like lettuce, it can be grown from transplants or from seeds. It is best to plant it regularly as it does not grow back very well. Its flowers are edible, and can be a nice peppery additions to salads, sauces, and grilled fish.