Types and days to harvest
| Type | What it is | Days to harvest |
|---|---|---|
| Leaf (loose-leaf) | No head; includes oakleaf and lollo types; the easiest to grow (UMN) | 41–50 (Cornell CCE); 48–58 (UW); 40–60 (UMN) |
| Butterhead | Soft, loose heads such as Bibb and Boston (UMD, UMN) | 55–80 (Cornell CCE); 42–70 (UW) |
| Romaine (cos) | Tall, upright heads | 70–85 for full heads (Cornell CCE); 50–70 (UW) |
| Crisphead (iceberg) | Dense, tight heads; the hardest type (UMD, Cornell CCE) | 80–95 (Cornell CCE); about 60–120 (UW) |
UNH gives 50–60 days for leaf and 60–85 for head lettuce, counted from germination. UW–Madison's guide, written for market growers, says all types but crisphead can be picked about three weeks early. UMD warns that crisphead needs a long, cool season, so leaf and butterhead suit small spaces best.
Timing in spring and fall
| Step | Figures given |
|---|---|
| Cold tolerance | "Hardy," growing in days as cool as 40°F (Colorado State); takes light frost but not heavy freezes (UMD, UNH) |
| Start indoors | 4–5 weeks from seed to transplant (UNH); about 4 weeks (UMN) |
| Set out transplants | 3–4 weeks before the last frost (UNH), after 2–3 days of hardening off with less water and cooler temperatures (UMN) |
| Direct sow | 2–4 weeks before the last frost (Colorado State); as soon as the soil can be worked (UMD, UMN, Cornell CCE) |
| Soil temperature | Minimum 35°F, optimum 70°F, measured 4 in deep at 8 a.m. (Colorado State) |
| Fall crop | Sow about three months before the average first fall frost (UMN); mid-July in northern New York (Cornell CCE, St. Lawrence County); romaine and crisphead in late July, leaf and Bibb mid-August to early September (Cornell CCE, Nassau County) |
Find your dates on frost dates explained; the planting calendar applies UNH's lettuce offsets. For fall, UNH suggests the varieties with the fewest days to maturity; since it counts from germination, add the 4–10 days seed takes to come up (Colorado State).
Sowing: shallow, cool and moist
- Depth. 1/8 inch, because lettuce needs light to germinate (UNH, UW); Colorado State and Cornell CCE say 1/4 inch, UMN 1/4–1/2 inch.
- Heat stops germination. UW says germination stops above 77–86°F depending on cultivar (its table puts the cutoff at 75°F soil); Colorado State lists 70°F as both optimum and maximum.
- Sowing in summer. Shade the soil and keep the top inch moist, watering several times a day if needed (UNH); sow thickly under row cover (Cornell CCE). UNH finds indoor starts "much easier and more reliable."
- Thin promptly. Crowded plants turn weak and spindly (Cornell CCE).
Succession sowing
One sowing gives a short harvest. UNH marks lettuce as a crop whose season "can be prolonged by doing multiple smaller 'sequence' plantings." The interval differs: every 7–10 days (Cornell CCE, Nassau County) or every 2–3 weeks while cool weather lasts (UW). UMD also suggests mixing varieties that mature at different times. In a small bed that means sowing a short row or a few square feet at a time.
- 1. Transplants set out 3–4 weeks before the last frost after 4–5 weeks indoors (UNH)
- 2. Direct sowing from 2–4 weeks before the last frost (Colorado State)
- 3. Re-sow every 7–10 days (Cornell CCE) to 2–3 weeks (UW) while it stays cool
- 4. Long days and heat bring bolting; UMN says several days above 75°F can trigger it
- 5. Fall sowing about three months before the average first fall frost (UMN)
- 6. Light frost is tolerated (UNH, UMD); row covers or low tunnels protect plants (UMN, UMD)
Bitter, bolting spring plantings are the signal to replant for fall (Cornell CCE, St. Lawrence County). UMN calls June through August generally too hot for lettuce in most of Minnesota.
Heat and bolting
Bolting is the plant sending up a flowering stalk and stopping leaf growth; the leaves turn very bitter (UMN). Purdue Extension notes it cannot be reversed once flowering has begun.
| Trigger | What sources say |
|---|---|
| Long days | Lettuce bolts as days grow longer in summer (Purdue); increasing day length and high temperatures usually cause bolting and bitterness (UMD); long days combined with heat (UW) |
| Heat | Multiple days above 75°F can trigger it (UMN); crisphead tends to form seed stalks after a few days above 75–80°F (Cornell CCE) |
| Preferred range | Nights around 50°F, days up to 68°F (UMN); days 65–70°F, nights 45–55°F (UW); butterhead best at 60–70°F (Cornell CCE) |
| Dry soil, strong light | Dry soil speeds flowering (Purdue); high light intensity contributes (UMN) |
Ways to hold it off, as the sources give them:
- Choose slow-bolting or heat-resistant varieties, such as oakleaf types (UMD).
- Shade the crop: shade cloth (UMD), lightweight enough to let some light through (UW), or plant where sweet corn, staked tomatoes or pole beans shade it during the hottest part of the day (UMD).
- Water evenly, about 1 inch a week (UMN).
- Pick spring crops before hot, dry weather (UMN); replace bolted plants with a summer crop (Purdue).
Tipburn (browned leaf edges): UW blames heat and low water uptake limiting calcium; UMN, growth resuming suddenly after a dry spell. Both point to steady moisture.
Containers and small beds
- Pot size: 1–3 gallons and 4–6 in deep for salad greens (UMD), or at least 2 gallons and 4–6 in deep for leaf lettuce (UW–Madison). See container sizes for vegetables.
- Mix: commercial potting mix, filled to the top, with no rocks in the bottom (UW–Madison).
- Light: at least six hours of sun for containers (UW–Madison); UMD says lettuce tolerates 4–6 hours and baby leaf can grow in summer's indirect light.
| Source | Leaf lettuce | Head lettuce | Rows |
|---|---|---|---|
| UMD | 4–8 in | 4–10 in (butterhead, cos); crisphead 12–15 in | 12–24 in (crisphead 20–30) |
| UMN | 5 in baby, 10–12 in full size | 6–8 in mini heads, 10–12 in full size | 18–30 in |
| Cornell CCE | 4–6 in | Large heads 12–14 in | 12–18 in |
| UNH | 6–10 in | 12 in | — |
| Colorado State | 7–9 in each way in blocks or close rows | — | |
For grid layouts, compare square foot gardening spacing.
Water and feeding
- Water frequently and lightly, overhead only in the morning (UMD); lettuce wilts most easily of the salad greens (UW). Mulch keeps soil cool and moist (Cornell CCE).
- Work in compost before planting; UMD rates lettuce's nutrient need medium-high.
Harvest and storage
- Leaf: pick outer leaves once plants are 5–6 in tall (UMD), until stems begin to bolt (Cornell CCE).
- Cut-and-come-again: sow a bed thickly, cut at 6–10 in just above the ground, and cut again 2–3 weeks later if watered and fed (UMD).
- Heads: romaine at about 4 in wide at the base and 6–8 in tall (UMD).
- Storage: 32°F and 95% humidity for 2–3 weeks; leaf and Bibb keep up to four weeks if bagged dry (UMD).
Common problems
| Problem | Signs | Extension guidance |
|---|---|---|
| Slugs and snails | Holes in leaves (UMN) | Row covers reduce slug and other pest feeding (UMD) |
| Cutworms | Young plants cut at the base (UMN) | Also listed by Cornell CCE |
| Aphids | Insects on leaves | They spread lettuce viruses (UW) |
| Aster yellows | Stunted, yellow plants (UMN); bitter taste (UW) | Spread by leafhoppers, no cure; row covers exclude them (UW) |
| Rots | Bottom rot, drop (UW) | Well-drained soil or raised beds, good spacing (UW); avoid the same spot year after year (Cornell CCE) |
This page gives no pesticide rates. Cornell CCE suggests taking a sample to your county extension office for identification; if you use any product, follow the label exactly.
Where sources disagree
| Question | Figures given |
|---|---|
| Succession interval | 7–10 days (Cornell CCE) vs 2–3 weeks (UW) |
| Seed depth | 1/8 in (UNH, UW); 1/4 in (Colorado State, Cornell CCE); 1/4–1/2 in (UMN) |
| Germination ceiling | 70°F (Colorado State); 75°F soil (UW table); 77–86°F by cultivar (UW text) |
| Sun | At least 6 hours in containers (UW–Madison) vs partial shade of 4–6 hours tolerated (UMD) |
| Soil pH | 6.0–6.5 (Cornell CCE); 6.0–6.8 (UMN); 6.0–8.0 (UW) |
Small-space checklist
- Leaf or butterhead types; slow-bolting ones as heat approaches.
- Transplants out 3–4 weeks before the last frost; seed barely covered and kept moist.
- A short row re-sown every one to three weeks while it stays cool.
- Shade, even water and early picking as heat arrives.
- Fall sowing about three months before the first fall frost.
- Pots of 2 gallons or more, 4–6 in deep.
More crop pages: tomatoes and peppers.
Sources
- University of New Hampshire Extension — Growing Vegetables: When to Plant Your Vegetable Garden (fact sheet)
- University of New Hampshire Extension — Cool Season Vegetables (Will Lowenthal, 2019)
- University of New Hampshire Extension — Fall Vegetable Gardening (Yard and Garden Infoline, 2020)
- Cornell Cooperative Extension of Nassau County — Lettuce (fact sheet B-1-18, reviewed 2003)
- Cornell Cooperative Extension of St. Lawrence County, Fruition — Ensuring a bountiful fall harvest with succession planting (Ken Kogut, 2021)
- University of Wisconsin–Extension — Growing Salad Greens in Wisconsin: A Guide for Fresh-Market Growers (Delahaut and Newenhouse, 2003, PDF)
- University of Wisconsin–Madison Extension — Growing Vegetables in Containers
- University of Maryland Extension — Growing Lettuce in a Home Garden (updated 2026)
- University of Maryland Extension — Types of Containers for Growing Vegetables
- University of Minnesota Extension — Growing lettuce, endive and radicchio in home gardens (reviewed 2024)
- University of Minnesota Extension — Planting vegetables in midsummer for fall harvest
- Colorado State University Extension — Vegetable Planting Guide (CMG GardenNotes #720, reviewed 2024)
- Purdue University Plant and Pest Diagnostic Lab, Picture of the Week — Lettuce Bolting (Rosie Lerner, 2021)
All sources were opened and checked in October 2026. Rules and figures change; confirm with the original before acting.