Bolting is when a vegetable crop “goes to seed”. A stem with seeds will shoot up through the middle of the plant. The plant is putting its energy toward reproduction—producing seeds instead of new vegetative growth.
A plant is done producing leafy vegetation when it bolts. Bolting is an irreversible process that indicates the plant is nearing the end of its harvestable lifetime.
Lettuce and many other crops tend to become very bitter and less tender after they have bolted. If you tear the leaves of lettuce, often times a milky substance will come out.
Basil is an exception. If you see that your basil is bolting, simply tear off the flowers and the plant will continue to put its energy into new basil leaf production.
What Causes Bolting?
Bolting can be caused by heat spells, cold spells, or changes to do the length of the day. All of these things are stressors that tell the plant that its end of life is nearing, and it needs to start producing offspring!
- Many crops such as spinach, cilantro, and lettuce are sensitive to high heat. Once temperatures get into the 80’s regularly, spinach will be the first garden crop to bolt.
- Certain crops are sensitive to photoperiod, or the number of hours of sunlight received each day. They go to seed once the amount of daylight changes.
- Biennial crops tend to flower in their second year due to changes in weather patterns, such as an extended cold spell or drastic temperature changes.
What can I do to prevent bolting?
- Try not to stress out the plants. Keep the soil moist and cool with mulch.
- Use a hail or shade protective cover to cool the garden in extreme heat.
With leafy green like lettuce, pick of the outermost leaves. This will slow down the maturing time for the plant and extend the growing season. Once a plant bolts, harvest it if it still tastes good and use that spot to re-plant quick crops like arugula, greens mixes, or bok choi, or save space for fall crops.