Crop guide · Vegetables
How to grow lettuce in containers: shallow, cool, and cut-and-come-again
Lettuce is the quickest, cheapest and most forgiving crop you can grow in a container. A tray 6 inches deep is enough, it is happy with part shade, and a cut-and-come-again mix gives three harvests from one sowing. This guide covers varieties that hold in heat, how to sow little and often, and how to keep a tray going from early spring into November.
- Container
- 6 in deep
- Width matters more than depth; a wide tray is ideal
- Sun
- Part shade
- 3–5 hours; midday shade in summer keeps it sweet
- Water
- Keep moist
- Shallow roots dry fast; never let it wilt
- First harvest
- 30 days
- Baby leaves from 3 weeks; cut-and-come-again gives three cuts
Varieties that work: Salad Bowl · Black Seeded Simpson · Little Gem · Marvel of Four Seasons · any cut-and-come-again mix. Trickier in pots: Large iceberg and crisphead types (slow, fussy, and they want more room than a tray gives).
Quick answer
Sow a loose-leaf or cut-and-come-again mix thinly across a container at least 6 inches deep, keep the mix moist, and give it three to five hours of sun with shade at midday in summer. Start cutting baby leaves at three weeks and whole leaves at four to five. Sow another pinch every two weeks so there is always a tray coming on, and move it into shade from June to keep it from bolting.
Why lettuce first
If you are starting a container garden and want something to eat soon, start with lettuce. It germinates in a week, tolerates a cheap, shallow container, does not need full sun, and gives you something to pick within a month. A single packet of seed, sown a pinch at a time, supplies salad for most of the year. It is also the crop most easily grown on a windowsill, a shaded balcony or a north-facing doorstep, where fruiting crops would struggle.
Choosing varieties
Lettuce comes in four broad types, and for containers the loose ones are the better choice.
- Loose-leaf varieties never form a head. You pick outer leaves or cut the whole plant an inch above the base and it regrows. Salad Bowl, Black Seeded Simpson, Red Sails and Lollo Rossa are all reliable, and most "cut-and-come-again" or "mesclun" mixes are built from them. These are the workhorses of a container.
- Butterhead types form a soft, loose head. Tom Thumb is small enough for a pot; Buttercrunch is a good all-rounder that tolerates some heat.
- Romaine (cos) types are upright and crisp. Little Gem is compact, fast and sweet, and fits eight to a window box.
- Crisphead (iceberg) types are slow, need cool weather for months, and want more room than a tray offers. Grow something else.
For summer, look for varieties described as slow-bolting or heat-tolerant: Jericho, Nevada and Muir hold longer than most. For fall and winter sowings, Winter Density and Marvel of Four Seasons cope with cold.
Containers and mix
Lettuce roots are shallow, so depth of 6 inches is enough and width is what gives you more plants. A window box, a shallow trough, a broad bowl or a 12-inch-wide pot all work. A seed tray or a mushroom crate lined with newspaper is fine for baby leaves. Drainage holes matter, because lettuce rots in soggy mix.
Use standard potting mix. Lettuce likes it moist and fairly rich, so there is no need to add grit, and a little slow-release fertilizer mixed in at the start carries a tray through its life.
Sowing
Sow directly into the container. Lettuce seed is small and wants light to germinate, so scatter it thinly over the surface, press it in, and cover with no more than a quarter-inch of mix or a dusting of vermiculite. Water gently with a rose and keep the surface moist until the seedlings show, usually in five to ten days.
The single most useful habit is sowing little and often. A whole packet sown at once gives you forty heads on the same day and nothing for weeks afterward. Instead, sow a pinch across a third of the tray every two weeks, or keep two trays going a fortnight apart. That is the difference between a steady supply and a glut.
Thinning depends on what you want. For baby leaves, leave the seedlings an inch apart and cut them young. For whole heads, thin to 6 inches for loose-leaf types and 8 inches for romaine or butterhead. The thinnings are your first salad.
Light
Lettuce is one of the few crops that does well with less sun. Three to five hours is ideal, and in spring and fall it will take more. Full sun in midsummer is the problem: heat above about 75°F makes lettuce bolt, meaning it shoots up a flower stalk and the leaves turn bitter. From June to August, move trays into afternoon shade, sow in the coolest spot you have, or grow a heat-tolerant variety. This is the one crop where a north-facing balcony is an advantage in July.
Water
Shallow roots mean lettuce dries out quickly and suffers fast when it does. A tray that wilts once will usually recover but tastes bitter afterward, and a tray that wilts repeatedly bolts. Check every morning in warm weather and water whenever the top half-inch is dry, aiming at the mix rather than the leaves. In hot spells that is daily. A thin mulch of fine compost between plants helps the surface stay moist.
Cut-and-come-again
This is the technique that makes lettuce worth growing in a small space. When loose-leaf plants are about 4 inches tall, cut the whole plant with scissors an inch above the crown, leaving the small central leaves. Water, and in two to three weeks it has regrown for a second cut. Most varieties give three cuts before the plant tires, and a sowing every two weeks keeps the cycle going.
For a longer-lived plant, pick the outer leaves individually and leave the center to keep producing. A single Salad Bowl plant treated this way crops for two months.
A season of lettuce
| When | What to do |
|---|---|
| Early spring | Sow as soon as the mix is workable; lettuce germinates at 40°F. Cover trays on frosty nights. |
| Late spring | Sow every two weeks. This is the easy season: enough sun, cool nights, steady growth. |
| Summer | Move trays into afternoon shade. Sow heat-tolerant varieties, keep watering daily, cut young. |
| Late summer | Start sowing again in the last week of August for fall crops. Cooler nights bring the flavor back. |
| Fall | Sow every two weeks into October. Growth slows but the leaves keep well on the plant. |
| Winter | In mild climates, a tray against a south wall keeps going. Elsewhere, a tray on a bright windowsill gives baby leaves. |
Common problems
| What you see | What it usually is | What helps |
|---|---|---|
| Plants shoot up and leaves turn bitter | Bolting from heat or drought | Move into shade, water daily, sow heat-tolerant types, cut young |
| Seedlings vanish overnight | Slugs or snails | Raise the tray off the ground, copper tape around the rim, check under it at dusk |
| Leaves pale and growth slow | Nutrients washed out | Liquid feed at half strength every two weeks |
| Brown, mushy lower leaves | Too wet, poor air flow | Improve drainage, water the mix not the leaves, thin the plants |
| Holes in leaves | Caterpillars or slugs | Pick them off; a fine mesh cover stops the moths laying |
| Seeds never came up | Sown too deep, or too hot | Sow on the surface; in summer, germinate indoors and move trays out |
Harvest
Baby leaves are ready at three weeks, whole loose-leaf plants at four to five, and heads at six to eight. Harvest in the morning when the leaves are crisp and full of water, and eat them the same day for the best flavor. Lettuce that has started to bolt is still edible if you cut it immediately, but it will not improve, so sow the next batch and move on.
Common questions
How deep does a container need to be for lettuce?
Six inches is enough; lettuce roots are shallow. Width matters more, because it decides how many plants you can grow. A wide, shallow tray beats a deep, narrow pot.
Does lettuce need full sun?
No. Three to five hours is ideal, and in summer full sun makes it bolt. A spot with morning sun and afternoon shade is close to perfect.
How often should I sow?
A small pinch every two weeks. One big sowing gives a glut and then nothing; staggered sowings give a steady supply.
Why does my lettuce taste bitter?
It has started to bolt, usually from heat or a dry spell. Cut it now, move the tray into shade, and keep the next sowing watered every day in warm weather.
Can I grow lettuce indoors?
Yes, for baby leaves. A bright south-facing windowsill gives enough light for a tray of cut-and-come-again mix through winter, and a small grow light makes it reliable.
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About the author
Carsten
Hi, I'm Carsten. My garden is paved over, so there is no soil to plant into and everything I grow lives in a container. I started this site to find out how much is possible that way, and I use it to share what I learn about choosing containers, growing useful plants in small spaces, and making gardening work for different homes and different bodies. Questions, corrections and photos of your pots are all welcome. say hello.