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Loose leaf lettuce is a cool-season crop with a fast turnaround, which gives it a different calendar from most vegetables. Rather than one sowing and one harvest, you run a continuous chain of small sowings that starts as soon as soil reaches 45F (7C) in spring, thins out through the heat of summer, and picks up again for a long, productive autumn window.
The two ends of that chain are the easy parts. The judgement lies in when to stop sowing into rising summer heat and when to start again as it falls, because sowing into a soil above 80F (27C) wastes seed and sowing too late in autumn leaves plants too small to survive frost.
| Stage | Trigger | Main jobs | Decision point |
|---|---|---|---|
| Late winter | Soil workable under cover | Sow in modules or under cloche | Whether the soil holds 45F (7C) |
| Early spring | Last hard frost passing | Plant out, start succession bands | Cover or not, given night lows |
| Late spring | Soil 55 to 65F (13 to 18C) | Sow every 2 weeks, pick weekly | Peak production, keep sowing |
| Summer | Days above 80F (27C) | Shade, mulch, water daily | When to pause sowing |
| Late summer | Nights beginning to cool | Restart sowing, chill seed | How early you dare start |
| Autumn | Soil 50 to 65F (10 to 18C) | Best quality of the year, pick heavily | Last sowing date before frost |
| Early winter | First hard frosts | Row cover, pick what remains | Clear the bed or overwinter |
Spring: getting the chain started
Start the first batch in modules under cover four to six weeks before your last frost, and sow the first direct band as soon as the soil holds 45F (7C). Both will be slow: expect ten to fourteen days to emerge and six or seven weeks to the first pick, which is roughly double the summer rate. That slowness is the reason for the wider three-week sowing interval in early spring.
As soil warms toward 55F (13C), tighten the interval to two weeks and the chain will start delivering continuously. Frost is a manageable risk for this crop; established loose leaf plants take a light frost without harm and only need row cover below about 28F (minus 2C), where outer leaves start to be damaged.
- Sow the first modules under cover Four to six weeks before the last frost, sow modules somewhere frost free. These give the earliest picking of the year by three or four weeks.
- Warm the first bed Cover the bed with row cover or a cloche for a fortnight before sowing to lift the soil to 45F (7C). Sowing into colder soil simply waits.
- Start the succession Once you are planting out, sow a fresh band every three weeks, tightening to two as the soil warms.
- Feed after the first cut Spring growth is slow and picking sets it back further. A half-strength liquid feed after each cut keeps the regrowth coming.
Summer: the difficult stretch
Once daytime temperatures sit above 80F (27C), everything about this crop gets harder at once. Germination falls off, established plants bolt in weeks rather than months, and the leaves turn bitter faster than you can pick them. This is the period to grow less lettuce rather than to fight for the same quantity.
What works is smaller, more frequent batches in the coolest part of the garden, chilled seed sown in the evening, thirty to forty percent shade cloth over the bed, an inch (25 mm) of mulch and daily watering at the base. What does not work is sowing the same size band in the same open bed and hoping. Expect two cuts from a summer sowing instead of four, and plan the kitchen around that.
| Summer problem | Cause | What actually helps |
|---|---|---|
| Seed does not come up | Soil above 80F (27C) | Chill seed 2 days, sow in the evening |
| Plants bolt at 4 weeks | Heat and long days | Shade cloth, pick earlier, sow smaller |
| Leaves bitter from the first pick | Moisture swings | Mulch and water daily at the base |
| Growth stalls entirely | Root zone above 85F (29C) | Move batches to afternoon shade |
Sowing continues through summer even at low success rates, because a partial band is still worth having and the chain must not break. Just sow half the usual length and expect half the stand.
Autumn: the best crop of the year
Autumn loose leaf is better than spring loose leaf in almost every garden. Soil temperature falls through the ideal 50 to 65F (10 to 18C) band, day length is shortening so bolting pressure drops away, and the plants grow steadily without the checks that cause bitterness. Sowings made as nights begin to cool will give four or more cuts each.
Work back from your first hard frost to set the last sowing date: loose leaf needs roughly six weeks from sowing to a first usable pick in cooling conditions, so a sowing six to eight weeks before the frost is the last one worth making unprotected. Under a cloche or low tunnel you can add another three or four weeks to that, and plants that have reached picking size will keep giving through light frosts.
| Weeks before first hard frost | What to sow | Expected outcome |
|---|---|---|
| 10 to 12 | Full succession bands | Four or more cuts each |
| 6 to 8 | Last unprotected sowing | Two cuts before growth stops |
| 4 to 6 | Sow under cloche only | Baby leaf through early winter |
| Under 4 | Nothing worth sowing | Clear beds and mulch instead |
Winter and the records that set next year's calendar
Established loose leaf plants under row cover or a low tunnel survive well below freezing and will hold, barely growing, through the coldest weeks. They do not produce much, but they resume quickly in late winter and give the earliest pick of the following year. Where winters are hard, clear the beds instead and use the time to add compost to the top six inches (15 cm) where the roots will be.
The records worth keeping are the calendar ones. Note the date of your first and last cut, the sowing date of the batch that bolted first in summer, and the sowing date of the last autumn batch that reached picking size. Those four dates, gathered over two seasons, define your own local sowing window far more accurately than any general guidance, because they are measured in your soil and your climate.
Also record which shaded position gave the best summer batch. Loose leaf is grown so many times a year that a single good microclimate in your garden is worth more than any change of method.