Lettuce bolting, also known as lettuce going to seed, is a common phenomenon in the garden. As temperatures rise and days lengthen in spring and summer, lettuce plants naturally transition from vegetative growth to reproductive growth and send up a tall, central stalk that will eventually produce flowers and seeds.
The change from leafy growth to upright, bitter-tasting flowering stalks signals the end of the growing season for most lettuce varieties. This often prompts questions from home gardeners about whether lettuce is still edible after it bolts.
What causes lettuce to bolt?
Lettuce is a cool weather crop that thrives in spring and fall when temperatures are between 60-70°F. Once temperatures climb above 75°F, most varieties will start to bolt as a survival mechanism to complete their life cycle and produce seeds before the extreme heat of summer.
Other factors that can trigger bolting in lettuce include:
- Excess nitrogen fertilization
- Drought stress
- Crowding
- Insufficient light
- Damage from insects or disease
- Variety not suited for the climate
Certain varieties of lettuce are more prone to bolting than others. Looseleaf types like oakleaf and Lollo Rossa are quick to send up a flower stalk, while compact butterhead and romaine lettuces are slower to bolt. Heat-tolerant varieties have been bred to withstand warm weather and resist bolting for a longer harvest period.
Effects of bolting on lettuce
Bolting changes both the texture and taste of lettuce leaves. Instead of forming a loose head or rosette of tender green leaves, the plant redirects its energy into growing a tall central stalk and leaves become smaller and more bitter tasting as they mature.
The milky, white substance known as latex flows through the stalk and leaves of bolting lettuce plants. Latex gives the leaves a bitter, unpalatable flavor. This is nature’s way of discouraging predators from eating the plant once it has transitioned to its reproductive phase and needs to survive until it sets seed.
In addition to bitterness, lettuce leaves often become tough and chewy when the plant bolts due to higher fiber content. The bitter taste combined with tough, rigid texture makes bolted lettuce unappealing for salads and sandwiches.
Can you eat lettuce after it bolts?
While lettuce past its prime may not be especially tasty, it is generally safe to eat after it bolts. There are no toxic compounds produced once lettuce starts flowering that would make the leaves dangerous to consume.
Keep in mind that older leaves have likely been exposed to warm weather, moisture, and potential contaminants in the soil for a longer period of time. This makes them more prone to spoilage from wilting and microbial growth. Carefully inspect leaves and discard any that are discolored, slimy, or foul smelling rather than simply bitter.
Tips for using bolted lettuce
If you want to salvage lettuce after it sends up a flower stalk, here are some tips:
- Pick only the small, tender, pale green leaves around the center. Older outer leaves tend to be exceedingly bitter and tough.
- Use bolted lettuce in cooked dishes instead of salads. Cooking helps mellow the bitter taste.
- Chop or shred lettuce finely and pair it with sweet or acidic ingredients to balance the bitterness.
- Try wilting lettuce in sautés, stir fries, soups, or braised dishes.
- Substitute bolted lettuce for radicchio or other bitter cooking greens.
- Lettuce flowers and immature seeds can be eaten or used to garnish plates.
Preventing lettuce from bolting
While lettuce quality deteriorates once it bolts, the appearance of flower stalks doesn’t necessarily mean the end of your harvest. Here are some techniques to keep lettuce growing strong a little longer:
- Provide shade or filtered sunlight if temperatures increase rapidly in spring.
- Use row covers or cloches to maintain cooler soil and air temperatures.
- Irrigate regularly to ensure consistent moisture.
- Choose bolt-resistant varieties suitable for warm climates.
- Stagger planting dates to ensure a continuous supply.
- Harvest individual leaves from the outer edges of the plant instead of pulling up the entire head.
- Cut or pinch off developing flower stalks to encourage leaf regrowth.
Key takeaways on eating bolted lettuce
- Lettuce becomes bitter, tough, and unpalatable once it bolts, but remains safe to eat.
- Older outer leaves tend to be very bitter and stringy compared to new growth.
- Cooked applications like stir fries and braised lettuce help reduce bitterness.
- Picking warm season varieties and maintaining cool temperatures can delay bolting.
- It’s normal for lettuce to bolt as temperatures rise, signaling the end of the main harvest period.
FAQ about lettuce bolting
Is bolted lettuce poisonous?
No, bolted lettuce is not poisonous or toxic in any way. The increase in bitter latex the plant produces once it flowers gives the leaves an unpleasant taste, but this latex is not dangerous to consume.
Can lettuce be eaten after flowering?
Lettuce can technically be eaten after it sends up a flower stalk and blooms, but the leaves often become so bitter, tough, and dry that quality really suffers. It’s best to harvest lettuce for salad use before flowering when leaves are still tender and mild. Once it bolts, use lettuce in cooked dishes instead.
Does lettuce get bitter as it gets older?
Lettuce leaves do tend to increase in bitterness with age, especially after the plant bolts. Warm temperatures prompt lettuce plants to produce more latex, which gives the leaves a bitter, milky juice. Outer leaves that have been growing the longest tend to contain the most latex and have a more pronounced bitter taste.
Can you eat lettuce after it seeds?
Lettuce can be eaten after it sets seeds, but seed production means it is past peak maturity and quality. Lettuce becomes increasingly tough, bitter, and fibrous once flowering begins. Seeds and young seed pods may be edible, but leaves deteriorate quickly after lettuce goes to seed.
Is it better to cut or pull lettuce?
Cutting individual lettuce leaves rather than pulling up the entire plant allows continued harvest after the center “heart” is removed. Use a sharp knife to remove outer leaves 1-2 inches above the base. Leave smaller inner leaves intact so the plant can continue to produce leaves from the center, prolonging the harvest.
What causes bitter lettuce?
Hot temperatures are the primary cause of bitter lettuce, prompting the plant to produce more milky latex as it bolts and flowers. Factors like crowding, poor nutrition, insufficient water, and age can also increase bitterness. Some lettuce varieties are naturally more bitter than others due to higher latex levels.
How can I use bitter lettuce?
Bitter lettuce can be salvaged by focusing on small, pale inner leaves and using cooking methods that mellow bitterness. Shred lettuce finely and pair with sweet or tangy ingredients. Try quick-cooking methods like stir frying or add to braised dishes, soups, and sautés. Bitter lettuce can be substituted for radicchio or other bitter greens.
Should I pull bolted lettuce plants?
Once lettuce plants bolt, the quality of leaves declines rapidly. At this point, it is best to remove spent plants and replant if extending the harvest is desired. Leaving cut off flower stalks may produce small secondary leaves, but they will still be bitter. Focus remaining lettuce plantings on heat-tolerant varieties selected for warm weather harvest.
How to grow bolt-resistant lettuce
While all lettuce will eventually bolt when exposed to high temperatures over time, some varieties hold off flowering longer than others under warm conditions. Here are tips for growing lettuce with better bolt resistance:
Choose appropriate lettuce types
The lettuce family contains a diverse range of plants with different susceptibility to bolting:
- Looseleaf – Fast to bolt, better for spring/fall harvests. Types: Red Sails, Black-Seeded Simpson.
- Butterhead – Slower to bolt than looseleaf. Types: Bibb, Boston.
- Romaine – Holds up to heat relatively well. Types: Valmaine, Tall Guzmaine Elite.
- Crisphead (Iceberg) – Very slow to bolt. Types: Ithaca, Calmar, Salinas.
In general, looseleaf lettuces bolt fastest while crisphead types resist flowering the longest in heat. Prioritize crisphead and romaine types for summer plantings.
Plant bolt-resistant varieties
Look for heat-tolerant, bolt-resistant varieties bred specifically for warm weather performance:
- Green Forest – Romaine type lasting up to 4 weeks longer than standard lettuces.
- Nevada – Heat-adapted crisphead suited for desert regions.
- Sierra – Romaine resisting bolting up to 5 weeks in summer.
- Concept – Crisphead lasting 2 weeks longer than normal.
- Summer Bibb – Butterhead standing moderate heat.
- Muir – Romaine with good bolting tolerance.
Provide optimal growing conditions
Creating the ideal environment helps delay bolting in lettuce:
- Grow lettuce in partial shade in summer or use shade cloth coverings to keep plants cooler.
- Use floating row covers or low tunnels to maintain cool soil and air temperatures.
- Ensure adequate moisture and avoid drought stress by regularly watering.
- Side-dress with nitrogen-rich fertilizer like compost or fish emulsion.
- Control insects and diseases promptly to prevent plant stress.
Stagger planting dates
Successively planting small batches of lettuce every 2-3 weeks ensures a steady supply as each planting matures. Use bolt-resistant romaine and crisphead types for midsummer plantings.
Harvest judiciously
Taking only outer leaves from lettuce plants instead of cutting the whole head leaves the plant intact longer before bolting. Leave the center leaves to continue growing and producing new leaves.
Conclusion
Lettuce bolting transforms plants from prime condition to overly bitter and fibrous as they flower and set seeds. But determining if lettuce is safe to eat after bolting depends largely on degree of bitterness and leaf texture. While quality suffers with age, lettuce does not contain toxic compounds in its latex or seeds that would make it dangerous. Cooked applications can improve bolted lettuces that are unacceptable for fresh eating. Timely planting of bolt-resistant varieties, maintaining cool conditions, and careful harvest help reduce unwanted flowering and extend the lettuce growing season.