What to do now
Mildest step first.
- Check the center of each plant; a rising stem means it has started to bolt.
- Keep plants that haven't started evenly watered and mulched, and shade them from afternoon sun.
- Harvest bolting plants whole and refrigerate the leaves; cook any that taste bitter.
- Pull the bolted plants and give the space to a warm-season crop; save the next lettuce sowing for late summer.
Not sure this is it? Check other lettuce problems
Is it bolting?
A lettuce plant that is bolting changes shape before it flowers. The center pushes up into a stem, the plant gets taller and looser, and heading types stop forming a tight head. The University of Illinois Extension says seedstalks form from a combination of long days, warm temperatures and age, and that lettuce may turn bitter in hot weather and once seedstalks begin to form. Bolting can't be reversed, so the useful questions are how much of the planting you can still eat and what to change for the next sowing. If your lettuce tastes bitter but hasn't started to stretch, heat alone may be the cause; see the bitter lettuce page.
Heat, long days and age
Lettuce grows best in cool weather. Illinois puts the sweet spot at an average daily temperature of 60 to 70°F, and Clemson Extension at 55 to 65°F; Clemson notes that Bibb lettuce turns bitter readily above 75°F. Spring days get longer whatever the weather does, so a planting still in the ground when the first warm spell arrives is primed to bolt. Illinois advises finishing spring planting at least a month before the hot days of early summer, and says crisphead types must mature before the first hot spell or they often fail. Sources weigh the triggers differently: Clemson puts high temperatures first, while Illinois and the University of Maryland Extension name lengthening days alongside heat.
Stress speeds it up
Anything that stresses the plant tends to bring bolting sooner. Clemson lists moisture stress along with heat as a reason lettuce turns bitter and bolts. The University of Maryland Extension warns that overly mature, stressed transplants are more likely to flower early, and that close spacing can encourage bolting. A six-pack of lettuce that sat for weeks, or a thick row that was never , is likely to go first. Maryland suggests spacing leaf, romaine and butterhead lettuce 4 to 10 inches apart, and frequent, light watering to keep plants growing quickly.
What to do now
Once the center starts to stretch, Illinois advises harvesting right away and storing the lettuce in the refrigerator. Cut whole plants rather than picking a few leaves at a time, since leaves tend to turn more bitter as the stalk grows. Taste first: Illinois says washing bitter leaves and refrigerating them for a day or two can help, and bitter leaves can also be cooked. For plants that haven't started, shade buys time. Maryland suggests planting lettuce where sweet corn, staked tomatoes or pole beans will shade it during the hottest part of the day, and notes that shade cloth helps protect lettuce from direct sun and high temperatures.
Next spring
Sow early. Leaf and butterhead lettuce can go in as soon as the soil can be worked, and Utah State University Extension suggests seeding 2 to 3 weeks before your . Sow small amounts every 10 to 14 days, as Illinois recommends, so one bolting planting doesn't end the season. Choose slow-bolting or heat-resistant varieties; Maryland names oak-leaf types as one example. Transplants 3 to 4 weeks old give an earlier harvest, Maryland says, so set them out young instead of holding them until they're overgrown. Where summers turn hot quickly, treat late spring as the end of the lettuce season: Maryland says lettuce does best grown only in the cool months of spring and fall.
Growing it again? When to plant lettuce for your ZIP code
- Why is my lettuce bitter?Bitter lettuce is usually a heat problem: warm weather, long days, and age push the plant toward bolting, and the leaves turn bitter first. Check the center for a rising stalk and harvest now if you see one.
- Why is my spinach bolting?Spinach bolts when spring days get long, and warm weather speeds it up. Once a center stalk rises, harvest the whole planting. Next time sow earlier, choose slow-bolting varieties, or grow it in fall.
- Why is my cilantro bolting so fast?Cilantro bolts when warm weather and long days tell it to flower; it is built to set seed before summer. Harvest what's left now, then sow small batches every few weeks in cool spring and fall weather.
- Why did my broccoli skip making a head and go straight to flowers?Broccoli bolts when it experiences heat or stress during head formation — once it starts flowering, the head is unsalvageable, but timing adjustments can prevent it next season.
- How many weeks before the last frost should I start seeds indoors?Count backward from your last frost date using the seed packet's weeks-to-transplant number — tomatoes usually go in 6–8 weeks before last frost, and peppers a little earlier, about 8–10 weeks.