One week the lettuce is perfect. The next, the center shoots up a tall stalk and the leaves taste bitter. That is bolting, and it is the most common disappointment with salad greens. It is also easy to plan around.
What bolting is
Bolting is the plant sending up a flower stalk to make seed. In lettuce and leafy greens it is triggered by high temperatures, long periods of strong light and drought. Lettuce grows best below about 75°F; long days and summer heat make it bolt and turn bitter. Cilantro does the same at the first hot spell.
It does not reverse
Once a plant has bolted, it will not go back. Pull it and sow again, either in cooler weather or in a shadier spot. If you let cilantro flower, the flowers attract beneficial insects and the seeds are coriander.
Five habits that delay it
- Sow early. Lettuce goes in 2–3 weeks before your last spring frost, so it grows in cool weather.
- Give afternoon shade once days get hot. A pot can move into the shade of a taller plant or a wall.
- Keep moisture even. Swings between dry and soaked make leaves tough and off-flavored.
- Sow a little, often. A new pinch of lettuce seed every 10–14 days means there is always a young batch coming on.
- Choose slower varieties. Oak-leaf lettuce types are slower to bolt; for cilantro, “slow-bolt” varieties buy a week or two.
Then try again in late summer
A second sowing 8–12 weeks before your first fall frost grows into cooling weather, which suits lettuce better than spring does.
Sources
Every fact in this guide comes from the publications below. None of them reviewed or endorsed Balcony Bounty.
- Iowa State University Extension. Growing Leafy Greens in Iowa. yardandgarden.extension.iastate.edu/how-to/growing-leafy-greens-iowa
- University of Maryland Extension. Growing Lettuce in a Home Garden. extension.umd.edu/resource/lettuce
- Utah State University Extension. How to Grow Lettuce in Your Garden. extension.usu.edu/yardandgarden/research/lettuce-in-the-garden
- University of Illinois Extension. Home Vegetable Gardening: Lettuce. extension.illinois.edu/gardening/lettuce
- University of Wisconsin–Madison Extension. Cilantro / Coriander, Coriandrum sativum. hort.extension.wisc.edu/articles/cilantro-coriander-coriandrum-sativum…
- Penn State Extension. Cilantro: A Unique Culinary Herb. extension.psu.edu/cilantro-a-unique-culinary-herb
- Oregon State University Extension. How to grow cilantro leaves or coriander seeds. extension.oregonstate.edu/news/how-grow-cilantro-leaves-or-coriander-s…
- University of Maryland Extension. Vegetable Succession and Companion Planting. extension.umd.edu/resource/vegetable-succession-and-companion-planting
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