How to Grow Lettuce (and Stop It Turning Bitter)
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Lettuce is one of the quickest and most rewarding crops you can grow. You can be eating salad a month after sowing, from a garden bed, a window box or a pot by the door. It has one firm rule: it likes cool weather. Respect that, and lettuce is nearly foolproof.
- When: early spring and again in late summer for fall. Lettuce grows best at 45 to 75°F.
- How: sow seeds barely covered, and keep the soil moist.
- Harvest: pick outer leaves from 4 inches tall, and the plant keeps producing.
- Bitterness comes from heat and age. Grow it cool, water it well, and pick it young.
Choose a type of lettuce
| Type | What it is like | Best for |
|---|---|---|
| Loose-leaf | Open bunches of tender leaves, green or red | Beginners. Fastest, and you can pick it leaf by leaf |
| Butterhead | Soft, loose heads with a buttery texture | Salads and wraps; good in pots |
| Romaine (cos) | Tall, crisp heads with sturdy ribs | Caesar salads; tolerates more heat than most |
| Crisphead (iceberg) | Tight, crunchy heads | Experienced growers with a long, cool season |
For a first crop, buy a packet of mixed loose-leaf lettuce. You get several colors and textures, and something to pick within a month.
A blend of leaf lettuces gives a ready-made salad from a single packet.
When to plant lettuce
- Spring: sow outdoors 4 to 6 weeks before your last frost, as soon as the soil can be worked. Lettuce seedlings tolerate light frost.
- Fall: sow again in late summer, about 6 to 8 weeks before your first fall frost. Fall lettuce is often the sweetest of the year.
- Summer: in hot climates, take a break or grow in shade. Lettuce seed sprouts poorly in soil above about 80°F.
- Mild winters: lettuce grows right through the cool season.
See when to plant vegetables for how to find your frost dates.
How to plant lettuce
- Pick the spot. Full sun in spring and fall. In warmer weather, a place with afternoon shade is better.
- Prepare the soil. Lettuce has shallow roots and likes loose, rich soil. Mix an inch of compost into the top few inches.
- Sow shallowly. Lettuce seed needs light to sprout. Scatter it thinly, press it onto the soil, and cover with no more than a quarter inch.
- Keep it damp. Water gently every day until seedlings appear, usually within 7 to 10 days.
- Thin. Leaf lettuce: 4 to 6 inches apart. Heading types: 8 to 12 inches apart. Eat the thinnings.
Sow a little, often. A short row every two weeks gives a steady supply. One big sowing gives you far too much lettuce for a fortnight and then none.
Growing lettuce in pots
Lettuce is ideal for containers because its roots are shallow. Use a pot or window box at least 6 inches deep with drainage holes, fill it with potting mix, and scatter the seed over the surface. Pots can be moved into shade when the weather warms. See container gardening for beginners.
A broad bowl holds a whole salad garden and is easy to move out of the sun.
Caring for lettuce
- Water: keep the soil evenly moist. Shallow roots dry out fast, and dry lettuce turns bitter. Aim for about an inch of water a week, in several light waterings.
- Feed: in rich soil, lettuce needs little. If growth is slow or pale, give a light dose of nitrogen-rich liquid fertilizer.
- Mulch: a thin layer of straw or compost keeps the soil cool and the leaves clean.
- Weed gently. Lettuce roots sit near the surface, so pull weeds by hand.
How to harvest lettuce
You have three options, and the first two keep the plant producing:
- Leaf by leaf. Once plants are about 4 inches tall, pick the outer leaves and leave the center to keep growing.
- Cut and come again. Cut the whole plant an inch above the soil with scissors. It regrows for a second, and often a third, harvest.
- Whole head. For butterhead, romaine and crisphead, cut the head at the base when it feels full and firm.
Harvest in the morning, when leaves are crisp and at their sweetest. Wash them in cold water, dry them well, and store them in the refrigerator in a container lined with a paper towel.
Why lettuce turns bitter, and how to stop it
Bitter lettuce is nearly always lettuce that is “bolting”. As days grow longer and hotter, the plant sends up a tall central stalk to flower and set seed. The leaves fill with a bitter, milky sap as it does.
| Cause | What to do |
|---|---|
| Heat, especially above 80°F | Grow in spring and fall. In summer, plant in afternoon shade or under shade cloth |
| Dry soil | Water consistently and mulch |
| Old plants | Harvest young, and sow a new row every two weeks |
| The variety | Choose types described as “slow to bolt” or “heat tolerant”. Romaine and some loose-leaf types cope best |
Once a plant bolts, the bitterness cannot be reversed. Pull it and sow again. If leaves are only mildly bitter, rinse them and chill them in the refrigerator for a day or two, which often improves the flavor.
A 30 to 40 percent shade cloth over hoops keeps lettuce cooler and delays bolting by weeks.
Common problems
| Problem | Likely cause | Fix |
|---|---|---|
| Ragged holes, slime trails | Slugs and snails | Pick them off at dusk; thin mulch near seedlings; water in the morning |
| Seedlings cut off at the ground | Rabbits | A low mesh fence. See how to keep rabbits out |
| Clusters of small insects | Aphids | Spray off with water. See how to get rid of aphids |
| Brown, crisp leaf edges | Tip burn, from uneven watering in warm weather | Water steadily; harvest sooner |
| Seeds do not sprout | Soil too hot, or seed buried too deep | Sow in cooler weather; barely cover the seed |
Frequently asked questions
How long does lettuce take to grow?
Baby leaves are ready in about 30 days, loose-leaf lettuce in 40 to 50, and full heads in 55 to 90 depending on type.
Does lettuce regrow after cutting?
Yes. Cut an inch above the soil, leaving the growing point, and most leaf lettuces regrow two or three times.
Can lettuce grow in shade?
It manages on 3 to 4 hours of direct sun, and in warm weather it prefers some shade.
Can I grow lettuce indoors?
Yes, on a bright windowsill or under a grow light. Loose-leaf types are the easiest.
