Lettuce bolting, also known as premature seed stalk formation, is a common issue that can ruin a seemingly thriving lettuce crop. As lettuce plants transition from vegetative growth to reproductive growth, the leaves become bitter, tough, and unusable. Fortunately, there are several methods gardeners can use to prevent or delay lettuce from bolting.

What Causes Lettuce to Bolt?

Lettuce is triggered to bolt and send up a seed stalk when the weather gets too hot. Each lettuce variety has an optimal temperature range, going above which signals the plant to shift from leaf production to flower production and seed setting. Here are some of the most common factors that cause lettuce bolting:

High Temperatures

Once temperatures rise above 75-85°F consistently, most lettuce varieties will start to bolt. Lettuce seeds germinate best at 55-75°F and grow optimally between 60-70°F.

Summer heat causes the plant to rush to set seed and complete its lifecycle before the extreme temperatures cause it to wither. Lettuce grown in hot summer climates bolts quickly without protection.

Temperature Fluctuations

Sudden spikes in day or night temperatures, even if brief, can trigger bolting. Average temperatures may be ideal, but plants are sensitive to extremes. Night temperatures below 55°F followed by days above 75°F often induce premature flowering.

Long Day Length

Lettuce is a long-day plant, meaning it blooms faster as daylight hours increase in spring and summer. Once the duration of daylight exceeds the critical day length for that variety, the plant is stimulated to bolt. Some varieties bolt after 13 hours of sun, while others may take 15+ hours.

Insufficient Watering

Moisture stressed lettuce will bolt more quickly. Drought conditions cause the plant to initiate reproductive growth and set seed before lack of water causes complete failure. Ensure consistent and sufficient water is provided, especially as temperatures rise.

Root Damage

Any root damage from transplant shock, cultivation, or pests can trigger bolting as the plant tries to complete its lifecycle. Minimize root disturbance when transplanting seedlings or thinning direct sown lettuce to prevent trauma.

Nutrient Imbalances

Insufficient nitrogen levels in the soil can lead to premature bolting. Too much nitrogen can make lettuce susceptible to tipburn. Maintain optimal nutrient levels with regular fertilization. Use compost and organic matter to improve fertility.

Tips to Prevent Lettuce From Bolting

The key to preventing lettuce from bolting is maintaining cool temperatures, steady moisture, and ideal growing conditions. Here are some tips to keep lettuce happy and actively growing leaves longer into the warm season:

Select Bolt Resistant Varieties

Certain lettuce types and cultivars are bred to be slow bolting. Look for heat-tolerant, slow bolting varieties. Leaf lettuces and looseleaf types resist bolting better than romaines and head lettuces. Red lettuces also tend to bolt more slowly.

Some recommended slow bolting lettuce varieties include:

Jericho Romaine
Little Gem
Merlot
Solaris
Pablo
Nevada
Salad Bowl
Black Seeded Simpson

Plant at Recommended Times

You can avoid the hottest weather by planting lettuce at the right time of year. In most climates,plant lettuce in early spring or late summer/early fall when temperatures are cooler. Avoid midsummer plantings.

In warm winter climates, lettuce can be grown as a cool season crop in fall through early spring. Time plantings so harvest occurs before temperatures exceed 75°F.

Provide Shade and Protection

Shield lettuce from hot sun and high temperatures. Plant in partial shade or use shade cloth hung over the lettuce bed to block 30-50% of the sun. Row cover fabrics also insulate plants and keep soil cooler.

Afternoon sun is hottest, so situate lettuce on the east side of taller crops or structures that provide afternoon shade. Lettuce thrives along with other cool-loving crops like spinach and kale.

Ensure Adequate Moisture

Consistent soil moisture prevents drought stress that can trigger bolting. Provide 1-2 inches of water per week. Use drip irrigation or soaker hoses to target the soil and avoid wetting foliage. Mulch around plants to retain moisture and keep roots cool.

Use Techniques to Keep Soil Cool

Mulching lettuce beds with straw, leaves, or grass clippings helps insulate soil and prevents wide temperature swings. Raise beds also improve drainage and aeration compared to planting in compacted soil at ground level.

White plastic mulch dramatically cools soil by reflecting sunlight. Black plastic warms the soil and should be avoided for lettuce.

Check Nutrient Levels

Test soil to ensure adequate but not excessive nutrients are present. Mix in several inches of compost or well-rotted manure before planting. Side dress growing lettuce with a balanced organic fertilizer or compost tea every 2-3 weeks.

Add a nitrogen rich fertilizer or mulch with grass clippings if leaves are pale and slow growing. Stop nitrogen fertilization as weather warms to prevent excessive levels.

Control Pests and Disease

Protecting lettuce from insects and diseases reduces stress and bolting triggers. Scout regularly for common lettuce pests like aphids, cabbage loopers, slugs, and flea beetles. Treat promptly if found.

Avoid wetting foliage when watering and allow for air circulation to prevent fungal and bacterial diseases. Remove any infected leaves promptly.

Time Succession Plantings

Rather than a large planting, stagger smaller lettuce plantings every 2-3 weeks. Harvest each planting before warm temperatures trigger bolting. Newer varieties may withstand more heat before bolting.

Successive sowing spreads out harvests for a steady supply. Direct sow or transplant seedlings of quick maturing varieties like ‘Salad Bowl’ and ‘Buttercrunch’ for replacement plantings.

Harvest Outer Leaves

Harvest outer lettuce leaves frequently, leaving the inner leaves to continue growing. Occasional cutting of older leaves encourages new growth without disturbing the plant. New leaves will be more tender than old outer leaves.

Once the center leaves start elongating into a seed stalk, the lettuce must be pulled or cut back to just above the root crown to prevent bolting. Timely harvesting is key.

Grow Lettuce Under Cover

Growing lettuce in a greenhouse, high tunnel, or cold frame allows much better control over the environment. Temperature, sunlight, ventilation, and moisture can all be moderated to prevent bolting.

lettuce can be grown in low tunnels, cloches, or under floating row covers inside a hoop house through summer for harvest into fall. Provide shade if necessary.

What to Do if Lettuce Bolts

Even with the best care, lettuce may occasionally bolt, especially as weather warms. At the first sign of bolting, here are some steps to take:

Harvest outer leaves promptly before quality declines further. New growth may still produce usable leaves.
Cut back the plant, leaving just the lower 2 inches of stem and small center leaves. New leaves may regrow.
Dig up the entire plant and replant if bolting is severe. Discard or compost bolted plants.
Direct sow lettuce seeds of heat tolerant varieties in the newly vacant space to replace bolted plants.
If lettuce is growing under cover, increase ventilation and shade to cool the environment. Ensure adequate moisture.
For fall crops, bolting can be expected as day length shortens and temperature cools. Plan last harvests accordingly.
Analyze why bolting occurred and make notes to adjust practices next season like altering planting dates, increasing shade, or selecting different varieties.

Common Questions About Lettuce Bolting

Can you eat bolted lettuce?

Once lettuce starts forming a flowering stalk, the leaves quickly become more bitter, tough, and unpleasant to eat. The milky white substance (latex) that oozes from cut stems also increases as lettuce bolts. Use young outer leaves promptly before quality suffers too much or discard the plant entirely.

What does lettuce look like when bolting?

The first sign of bolting is elongated center leaves and stem. A tall stalk will then rapidly emerge from the center of the lettuce plant. Once the stalk reaches 6-12 inches, small yellow flowers develop, followed by seed pods. Leaves become sparse, bitter, and tough.

Should you cut lettuce when it bolts?

Cutting back a bolting lettuce plant can possibly encourage new leaf growth if you remove all but 2 inches of the stem. However, the lettuce is unlikely to produce many quality leaves before bitter latex taints the plant. It is usually best to pull spent lettuces and replant.

Can lettuce bolt without flowering?

Lettuce plants will elongate and send up stalks before flowers emerge once stimulated to bolt. So leaf quality can decline well before you see the characteristic tall stalk with yellow blossoms. Monitor plants closely for the earliest signs of bolting to maximize harvest.

Is lettuce a cold weather crop?

Definitely. Lettuce grows best in cool weather between 60-75°F. It thrives as a fall crop in most climates. Lettuce can even be grown through winter in cold frames or unheated greenhouses in some regions. Hot summer temperatures quickly cause bitter, tough leaves and bolting.

Conclusion

Bolting is frustrating but not entirely unavoidable, especially as seasons transition. However, you can significantly delay lettuce from bolting by selecting suitable varieties, timing plantings carefully, providing insulation from heat, and maintaining optimal growing conditions. With close observation and quick action as weather warms, you can still enjoy harvests of sweet, tender lettuce before a long hot summer triggers bolting.

How to Stop Lettuce From Bolting: A Comprehensive Guide

Preventing lettuce from bolting takes careful variety selection, ideal growing conditions, and proper care. Follow these tips to keep lettuce actively growing lush leaves, not bitter flower stalks.

Choosing Bolt Resistant Lettuce Varieties

Prioritize heat tolerance and slow bolting when selecting lettuce cultivars. Leaf lettuce types resist bolting better than head lettuce.
Recommended slow bolting lettuce varieties: Jericho Romaine, Little Gem, Merlot, Solaris, Pablo, Nevada, Salad Bowl.
Red lettuces like Merlot and Red Sails are often slower bolting than green varieties.

Providing the Right Conditions

Grow lettuce in the cool seasons of early spring and fall when air temperatures are mild, around 60-75°F.
Start seeds indoors 6 weeks before your last frost to transplant outdoors after hardening off.
In summer, plant lettuce in partial shade or use shade cloth to block 30-50% of direct sunlight.
Use floating row covers over lettuce beds to provide insulation from heat and cold extremes.
Ensure lettuce receives consistent moisture. Drought stress encourages early bolting.
Avoid disturbing roots when transplanting and thinning to prevent trauma that can induce bolting.

Maintaining Optimal Care Through Harvest

Test soil and amend with compost and organic fertilizer to provide balanced nutrition if needed.
Side dress growing lettuce with compost tea or organic fertilizer every 2-3 weeks for slow steady growth.
Control pests like aphids that can add stress and trigger bolting. Scout regularly and treat any infestations promptly.
Harvest outer lettuce leaves frequently, at least once a week. Cutting older leaves encourages new growth.
At the first sign of lettuce bolting, either harvest promptly or cut back plants to just above the root crown.

Grow Lettuce Successfully Through Summer

Time succession plantings 2-3 weeks apart to ensure harvest before heat triggers bolting.
Use cloches, cold frames, or shaded tunnels to grow lettuce in midsummer. Ventilate to prevent excess heat buildup.
Make notes on which varieties grew the longest before bolting to adjust future plantings.
When lettuce inevitably bolts as summer progresses, remove spent plants and direct sow more heat tolerant varieties as replacements.

Common Questions About Bolting Lettuce

Why does lettuce get bitter as it bolts?

The milky latex that gives lettuce leaves their bitterness increases as the plant shifts energy to flowering rather than leaf production. Hot temperatures speed up latex production.

Can lettuce rebloom after bolting?

Lettuce is generally finished after the initial stalks emerge and flowers form. However, cutting back plants promptly after spotting bolting can possibly encourage some new leaves before bitterness takes over.

Should I compost lettuce gone to seed?

Spent lettuce plants with seed stalks can be composted without much concern about viability. Temperatures in active compost piles get hot enough to destroy lettuce seeds, preventing volunteers next season.

How long does lettuce take to bolt?

Lettuce grown in ideal 60-70°F temperatures may take 6 weeks or longer before bolting. In summer heat, lettuce can bolt within just 2-4 weeks after germinating or being transplanted outdoors. Hotter temperatures accelerate the process.

Can lettuce withstand frost?

Lettuce can tolerate light frosts by going dormant. Cover plants or use row covers if hard freeze conditions threaten. The biggest frost risk is to young seedlings that lack hardiness – delay transplanting until soil warms.

Conclusion

Preventing lettuce bolting requires close observation, prompt harvesting of outer leaves, providing insulation from heat, and maintaining optimal soil fertility and moisture. With attention to growing conditions and variety selection, you can maximize your lettuce crop through the season.

How to Stop Lettuce From Bolting: A Step-By-Step Guide

Follow these key steps to keep lettuce growing vigorously and delay premature bolting as long as possible:

Step 1: Select Varieties Bred to Resist Bolting

Prioritize heat tolerance and slow bolting traits when choosing lettuce to grow.
Leaf lettuces like green and red oakleaf resist bolting better than crisphead types.
Looseleaf lettuces like ‘Salad Bowl’ and ‘Black Seeded Simpson’ are goodbolt resistant options.
Romaine lettuces like ‘Little Gem’ and ‘Jericho’ stay vegetative longer than many others before shooting up flower stalks.

Step 2: Time Plantings for the Cool Season

Start lettuce seeds indoors 6-8 weeks before your last average frost date.
Harden off and transplant lettuce outdoors once soil warms to at least 40°F.
For fall crops, start seeds in midsummer to maturity and harvest in cool fall weather.
In mild winter climates, sow lettuce in late fall or early winter for early spring harvest before heat.

Step 3: Provide Protective Shade

Grow lettuce in the partial shade of taller plants or structures that block 30-50% of direct sun.
Drape shade cloth over lettuce beds to filter direct sunlight and prevent leaf overheating.
Build temporary shelters covered with shade cloth to grow lettuce through summer heat. Ventilate to prevent excess humidity.

Step 4: Use Row Covers for Insulation

Cover lettuce with floating row cover fabric stapled over hoops to create a protective tunnel.
Row covers boost temperatures in early spring, retain heat at night and block hot sun during the day.
Ensure lettuce does not overheat under row covers on hot sunny days – ventilate as needed.

Step 5: Maintain Steady Soil Moisture

Water lettuce regularly to keep soil consistently moist but not saturated. Drought stress causes bolting.
Time watering for early morning to allow leaves to dry out during the day – wet foliage encourages disease.
Mulch around lettuce with straw, leaves or grass clippings to retain soil moisture and prevent wide temperature fluctuations.

Step 6: Scout for Pests and Control Promptly

Monitor frequently for aphids, slugs, cabbage loopers and flea beetles.
Wash off aphids with a strong spray of water. Apply insecticidal soap for heavy infestations.
Pick off loopers and slugs by hand or apply organic baits like Bt or iron phosphate.
Manage pest stresses properly to avoid triggering premature bolting.

Step 7: Harvest Outer Leaves Frequently

Cutting older outer lettuce leaves often encourages new tender leaf growth inside the plant.
Harvest individual leaves with a sharp knife, leaving the core intact to regrow.
Timely harvesting maximizes productivity and removes nutrient rich older leaves attracting pests.

Step 8: Take Action at First Sign of Bolting

At the initial sign of lettuce bolting, harvest all mature outer leaves promptly.
Cut back the plant, leaving just 2 inches of stem and small center leaves which may continue producing.
Pull out severely bolted plants entirely and replant the area with more heat tolerant varieties.
Ensure lettuces growing under cover are properly ventilated and shaded as weather warms.

Conclusion

Paying close attention to lettuce plants, maintaining ideal growing conditions, and prompt harvesting are the keys to preventing premature bolting. Follow these steps to keep lettuce actively growing lush leaves, not bitter flower stalks.

How to Stop Lettuce from Bolting

Lettuce bolting, or prematurely shooting up flower stalks, is a common frustration for gardeners. Hot weather triggers lettuce to bolt, causing bitter, tough leaves before the crop reaches full maturity. Fortunately, you can take steps to prevent or delay lettuce bolting.

Choose Heat-Tolerant Varieties

Prioritize heat tolerance and slow bolting when selecting lettuce varieties. Leaf lettuces resist bolting better than head types.
Little Gem, Merlot, Salad Bowl, Nevada – these lettuces stay vegetative longer before bolting.