How to Grow Butterhead (Bibb) Lettuce: 60–70 Days to a Loose Head, and Why Leaves Touching Wet Soil Rot First

Butterhead lettuce takes about 60 to 70 days from sowing to a soft, cupped head weighing 4 to 8 ounces, and it wants average daily temperatures between 60 and 70°F to get there. That is Illinois Extension’s figure for the type; Iowa State says about 70 days. Clemson warns that Bibb “will develop bitterness readily” once temperatures go above 75°F. What most guides skip is what ends a butterhead crop in a wet spell: its soft outer leaves rest against the soil, and that contact point is where bottom rot starts, while wet soil at the crown feeds white mold.

This spoke of our zone-by-zone lettuce growing guide covers the butterhead-specific parts: how long it really takes, which cultivar to pick, when to sow, what bolting looks like, and how to keep the lowest leaves off wet ground. One claim you’ll see repeated online, that butterhead bolts later than romaine, didn’t survive a check against the sources, and the bolting section below explains why.

How Many Days Does Butterhead Lettuce Take to Mature?

Plan on 60 to 70 days from sowing for a full butterhead. Published figures run from 28 to 70 days because they measure different things: baby leaves, a small head, or a full one.

The takeaway: 46 days is one cultivar’s best case, while the two extension figures for the type cluster at 60 to 70. Build your calendar on 70 days and be pleased when the heads come early.

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Butterhead sits between leaf lettuce (50 to 60 days by Illinois’s count, 40 to 45 by Iowa State’s) and crisphead, which Iowa State puts at 70 to 80. That is a lead of up to about 10 days over iceberg, not the multi-week head start you sometimes see claimed, and it’s the reason butterhead is the more forgiving choice when spring is short.

Is Bibb Lettuce the Same as Boston Lettuce?

For growing purposes, yes: extension pages treat Bibb and Boston as one loose-heading group, and the size differences come from the cultivar, not the name. University of Maryland Extension lists “Bibb and Boston” as examples of the same type, Virginia Tech writes “butterhead, or Bibb lettuce,” and Clemson files ‘Buttercrunch’ and ‘Esmeralda’ under Boston type. In shops and catalogs the names usually split by size, with Bibb for the small, tight head and Boston for the bigger, looser one. Treat that as a naming habit rather than a botanical line.

What does matter at planting time is head size, because it sets your spacing. Here are four butterhead cultivars with the sizes and spacings the sources give:

Extension spacing for the type runs from 6 to 8 inches (Illinois) to 12 to 14 inches (Iowa State). For a Boston-sized head like ‘Buttercrunch,’ 8 to 10 inches is the figure most sources agree on; go down to 6 inches only for the miniatures. Our lettuce varieties guide covers loose-leaf and cut-and-come-again types if you want something that regrows.

When Should You Plant Butterhead Lettuce?

Sow so the head finishes before your days start averaging above about 75°F, which means counting back about 70 days from that date. The numbers behind the rule are consistent across sources: Illinois says lettuce thrives at average daily temperatures of 60 to 70°F, Clemson says Bibb turns bitter above 75°F (Virginia Tech says it “will develop bitterness readily” in heat), and Johnny’s says seed germinates best below 70°F.

For a spring crop, use this count-back:

1. Find the week your afternoon highs usually reach the mid-70s.
2. Subtract 70 days (10 weeks). That is your direct-sowing date. If highs reach the mid-70s around June 15, sow around April 6.
3. If you start transplants indoors, UC Master Gardeners suggest sowing seed 4 weeks before planting out, and Johnny’s says transplants cut 10 to 14 days off the garden clock.

Illinois Extension’s bare minimum is to finish spring planting at least a month before the really hot days begin. That cushion gives you baby leaves and outer-leaf picking (Johnny’s lists baby size at 28 days), not a cupped head, so don’t treat it as a full-head deadline.

Seeds are also a heat problem, not just plants. Johnny’s notes that lettuce seed goes into thermal dormancy at high temperatures, so a late-summer sowing into hot soil can sit there without coming up. Iowa State says seedlings emerge in 7 to 10 days when the soil stays moist, so a patch still bare after two weeks of hot weather points to the heat rather than the seed. For fall crops, Illinois says plantings started in late summer “mature during cool fall weather.” Our guides to growing lettuce from seed and summer sowing cover the germination tricks.

Regional planting windows from extension sources

In the warm-winter examples above, lettuce becomes a fall-through-early-spring crop. Start from your own heat date, not a zone number.

Does Butterhead Bolt Later Than Romaine?

Not as a type, as far as I could find: the evidence says the cultivar decides, and the most popular butterhead, ‘Buttercrunch,’ landed in the less heat-tolerant group in the one trial that named it. I couldn’t find an extension or peer-reviewed source that ranks butterhead against romaine for bolting. Rankings that circulate online aren’t consistent with extension guidance (one I found put crisphead as the slowest to bolt, while Illinois calls crisphead “extremely sensitive to heat”).

What the sources do show:

• A heat trial split cultivars, not types. Auburn University researchers grew 18 cultivars in a hydroponic greenhouse (sown 30 June and 19 August 2016) and rated bolting and tipburn. ‘Parris Island,’ ‘Sparx,’ ‘Aerostar,’ ‘Monte Carlo,’ ‘Nevada,’ ‘Salvius,’ ‘Skyphos’ and ‘Adriana’ tolerated heat better than nine others, including ‘Buttercrunch.’ It was a greenhouse water-culture trial, so it can’t be read as a garden-bed result, but it is the only head-to-head data I found.
• Slow-bolting cultivars exist in both types. UC Master Gardeners list ‘Rhapsody’ as a slow-to-bolt butterhead and ‘Cimarron’ as a slow-to-bolt romaine.
• The type-level hint is about timing. Butterhead’s 60 to 70 days is shorter than crisphead’s 70 to 80 (Iowa State), so it can finish before heat arrives. That’s a head start, not heat tolerance.

Bolting itself is driven by more than temperature. Illinois Extension attributes seedstalks to “a combination of long days, warm temperatures and age,” and a 2022 BMC Genomics study found that heat-induced bolting involves genes in three flowering pathways: photoperiod, age and gibberellin. Age is one of those three triggers, so a butterhead left standing past its prime is a bolting risk even in moderate weather. For a head-to-head look at the two types, see our butterhead vs romaine comparison; the practical rule is to choose a labelled slow-bolting cultivar and harvest on time.

You can taste the point of no return. UC Master Gardeners note that bolting leaves turn bitter, especially the ribs, and that milky sap in a cut leaf instead of clear sap is a sign the leaves will taste bitter. Snap a rib on a plant that’s thinking about bolting: milky sap means harvest now.

How Do You Plant and Care for Butterhead Lettuce?

Give butterhead loose, well-drained, fertile soil and steady light watering, because it has shallow roots. Virginia Tech recommends a well-drained, loose loam with rich fertility, and Maryland Extension suggests working compost in before planting.

• Water often and lightly. UC Master Gardeners describe lettuce as shallow-rooted and in need of frequent watering when there’s no rain, and Illinois says frequent light watering produces rapid leaf growth and high-quality lettuce. Uneven water also feeds tipburn, which UC IPM ties to water stress and slow transpiration.
• Don’t overdo it. Maryland Extension warns that over-watering contributes to root and leaf diseases, which is the rot problem covered in the next section.
• Mulch with organic material. Illinois says organic mulches moderate soil temperature and the microenvironment, helping lettuce in less-than-ideal weather. Virginia Tech prefers organic mulch to black plastic once the soil warms.
• Space for the head you want. See the cultivar table above: 6 inches for miniatures, 8 to 10 for Boston-sized heads.

Why Does Butterhead Rot Where the Leaves Touch Wet Soil?

Two different soil fungi attack the lowest leaves, one in warm wet weather and one in cool wet weather, so a butterhead can rot in spring, in fall or in a wet summer. Both start at the soil line.

The takeaway: warm wet weather drives bottom rot and cool wet weather drives lettuce drop, so wet soil is the shared risk across seasons. Illinois Extension puts it plainly: “Foliage rots can be a problem, especially in hot or wet seasons.”

Here is where butterhead’s growth habit matters. Delaware’s advice is to “plant lettuce varieties with an upright architecture to reduce foliage contact with the soil.” A butterhead rosette tends to carry its soft outer leaves low, close to the ground, which is the opposite of that architecture. To be straight about the evidence: no source I found compares butterhead and romaine rot rates directly, so “butterhead rots faster” is a reasonable inference from the architecture, not a measured result. And no fungicide fixes it: UC IPM says none is effective against Rhizoctonia on lettuce, so prevention is the whole strategy.

How to keep the leaves off wet ground

1. Raise the bed. Delaware recommends high beds for air movement and drainage, and UC IPM wants beds “as high as possible” and the surface kept “as dry as possible with careful irrigation.”
2. Lay a dry organic mulch between the plants and the soil. Straw or similar organic material turns a wet-soil contact point into a dry one. I found no trial that measured mulch against bottom rot in home beds, so this is guidance from the mechanism, not from a study. Use clean material, and keep it from piling against the crown.
3. Don’t dig in fresh residue. UC IPM says to avoid planting lettuce where large amounts of undecomposed plant residue sit in the soil, since it probably helps Rhizoctonia survive.
4. Rotate. Delaware recommends three or more years away from lettuce hosts, and UC IPM names beans, celery and tomato among the crops to avoid before lettuce when lettuce drop is the worry.
5. Pull sick plants. UC IPM recommends removing infected plants to reduce the fungus in the bed.
6. Ease off watering near harvest. Delaware says to avoid irrigation close to harvest.

Butterhead Lettuce Problems: Symptom, Cause and Fix

Most butterhead failures trace back to heat, wet soil or uneven water, and the symptom tells you which. For the wider list, see our lettuce growing problems guide.

When and How Do You Harvest Butterhead Lettuce?

Harvest when the leaves begin to cup inward into a loose head, usually at 4 to 8 ounces. Maryland Extension and Virginia Tech both use that cupping as the maturity sign, and Illinois gives the weight. UC Master Gardeners say to take heading types when firm but not hard, and butterhead is a loose head by design, so don’t wait for a tight ball.

• Pick outer leaves early. Iowa State and UC Master Gardeners both note that outer leaves can be harvested before the head matures, which prolongs the crop if heat is approaching.
• Cut at the base. Take the whole head just above the soil line when it cups.
• Eat the heart. The innermost leaves blanch themselves, and Illinois Extension calls them a delicacy.

If you’d rather harvest in small pieces all season, our guide to cut-and-come-again harvesting covers the leaf-lettuce method.

Butterhead Lettuce FAQ

How long does butterhead lettuce take to grow?

Butterhead takes about 60 to 70 days from sowing to a loose, cupped head, per Illinois and Iowa State Extension. Seed-company figures as short as 46 days describe a specific cultivar under ideal conditions.

How far apart should butterhead lettuce be planted?

Space Boston-sized butterheads like ‘Buttercrunch’ 8 to 10 inches apart and miniatures like ‘Tom Thumb’ about 6 inches apart. Extension figures for the type range from 6 to 14 inches, depending on how big you want the head.

What temperature does butterhead lettuce grow best in?

Average daily temperatures of 60 to 70°F suit it best. Above about 75°F, Bibb turns bitter, according to Clemson, and heat, long days and age combine to trigger bolting.

Can you grow butterhead lettuce in summer?

You can try it, but UC Master Gardeners recommend planting where other crops or trees give shade and choosing slow-bolting cultivars such as ‘Rhapsody.’ Expect to harvest early and often, since heat shortens the window.

Why is my butterhead lettuce bitter?

Heat and bolting are the usual causes. Milky sap in a cut leaf is a sign it will taste bitter, and bitterness is strongest in the ribs; harvest the rest of the crop now rather than waiting.

Sources

1. University of Illinois Extension. Lettuce. Gardening and Horticulture
2. Haynes, C. Lettuce (2009). Iowa State University Extension, Yard and Garden
3. Clemson Cooperative Extension. Lettuce. Home and Garden Information Center
4. University of Maryland Extension. Planting Lettuce in a Home Garden
5. Virginia Cooperative Extension. Lettuce (Publication 426-408). Virginia Tech
6. Johnson, G. Lettuce Bottom Rot, Rhizoctonia solani (June 11, 2021). University of Delaware Cooperative Extension, Weekly Crop Update
7. UC Statewide IPM Program. Rhizoctonia Diseases, Lettuce Pest Management Guidelines. University of California Agriculture and Natural Resources
8. UC Statewide IPM Program. Lettuce Drop, Lettuce Pest Management Guidelines. University of California Agriculture and Natural Resources
9. UC Statewide IPM Program. Tipburn, Lettuce Pest Management Guidelines. University of California Agriculture and Natural Resources
10. UC Master Gardeners of Santa Clara County. Lettuce. University of California Agriculture and Natural Resources
11. Johnny’s Selected Seeds. Buttercrunch Organic Lettuce Seed
12. Holmes, S.C., Wells, D.E., Pickens, J.M. and Kemble, J.M. Selection of Heat Tolerant Lettuce (Lactuca sativa L.) Cultivars Grown in Deep Water Culture and Their Marketability. Horticulturae 5(3):50 (2019). DOI: 10.3390/horticulturae5030050
13. Hao, J. et al. Molecular Basis of High Temperature-Induced Bolting in Lettuce Revealed by Multi-Omics Analysis. BMC Genomics 23:580 (2022)