Bolting happens when a plant reaches the end of its growth cycle. It changes from making leaves and roots to making flowers and seeds for the next season of plants. That is why bolting is often called "running to seed" or "going to seed."
Bolting is normal, but can be a problem for gardeners when it happens before they get a full harvest of vegetables. When the plant is stressed, often by heat or amount of sunlight, it is more likely to bolt. While the plant is rushing to make seeds, it is also making tough and bitter leaves as a way to protect itself until the seeds are ready.
Plants that are more likely to bolt are lettuce, other leafy greens, basil and cilantro. To slow down bolting and enjoy more tasty leaves, the gardener can do a few things:
- Plant cool-weather plants in the spring (or early fall for some) when days are cooler and shorter.
- Protect plants from too much sun and heat with shade cloth or by planting in shady areas or near larger plants that provide shade. If you are growing in containers, move plants to a shady area if you can. Light-colored and large containers will help keep roots from overheating.
- Look for slow-to-bolt varieties when buying seeds or plants.
- Put a layer of mulch around plants to cool the soil.
- Trim back growing leaf stalks or flower buds as soon as you see them.