How to Grow Lettuce

There are hundreds of varieties of lettuce (Lactuca sativa), from soft and delicate bibb lettuce to crisp and colorful rouge d'hiver. This easy-to-grow annual is a classic for beginner and expert gardeners alike. Most types of lettuce grow quickly, maturing in five to eight weeks. And many are suitable for cut-and-come-again harvesting, so you can snip off a few leaves anytime you want a salad. Lettuce is a cool-season vegetable, and in most home gardens it is planted in the early spring and harvested in late spring to early summer. Some gardeners plant a second crop of lettuce as the days grow cooler in fall.

Lettuce can be divided into four major categories: head lettuce, romaine/cos, leaf lettuce, and butterhead (loose head). Leaf lettuce has the greatest number of varieties available and is the most popular type for home gardens.

How to Plant Lettuce

When to Plant

Plant lettuce in the spring as soon as the soil can be worked. Or, start seeds inside around five weeks before your area's projected last spring frost date. You can continue sowing seeds every two weeks to have a continual harvest if you wish. For a fall harvest, plant roughly seven weeks before the first fall frost.

Selecting a Planting Site

Choose a fairly sunny growing site with well-draining, organically rich soil. Container growth is also an option. To maximize the efficiency of your garden, plant lettuce among warm-season vegetables, such as tomatoes. By the time the lettuce is finished in early summer, the warm-season vegetables will be actively growing and able to take over the space. Also, aim to plant lettuce in a different spot each season to reduce the risk of soil-borne diseases.

Spacing, Depth, and Support

Plant seeds only around 1/8 to 1/4 inch deep, as they need light to germinate. Space rows at least a foot apart. The space between seedlings depends on the mature width of the variety. But in general, keeping lettuce plants fairly close together will help to suppress weeds. A support structure shouldn't be necessary.

Lettuce Plant Care

Light

Full sun, meaning at least six hours of direct sunlight on most days, is ideal for lettuce. But it also will grow in partial sun and does appreciate some shade in warm climates. However, too much shade can make the growth leggy and weak.

Soil

Lettuce likes soil that's light, rich in organic matter, and well-draining. A neutral to slightly acidic soil pH is best.

Water

Like with other salad greens, it’s important to maintain even soil moisture for lettuce. If the soil gets too dry, the plants might bolt, or send up flower spikes and go to seed, which turns the leaves bitter. Dry soil also can cause the leaves to become sun-scorched. It’s best to water regularly throughout the week anytime the top inch of soil feels dry to the touch versus doing one weekly deep watering. 

Temperature and Humidity

Lettuce grows best in a temperature range between roughly 45 and 70 degrees Fahrenheit. Hot weather can turn the leaves bitter. For summer plantings, it is important to select varieties with heat tolerance. Some lettuce varieties can tolerate a light frost but not a freeze. Humidity typically isn't an issue for lettuce as long as adequate soil moisture is maintained and there's airflow around the plants.

Fertilizer

Work compost into the soil before planting to enrich it with organic matter. Then, use a fertilizer that's high in nitrogen starting around three weeks after planting, following label instructions. This will help to promote healthy, vigorous leaf growth.

Pollination

Lettuce is a self-pollinated crop.

Types of Lettuce

For practical purposes, lettuce is divided into four distinct groups:

• Crisphead forms a firm head with a crisp texture and distinct veins. Iceberg is the most commonly grown commercial variety.
• Butterhead also forms a head, but the texture is more soft and pliable with less distinct veins compared to crisphead.
• Looseleaf forms a kind of bunch instead of a head. Looseleaf lettuce can regrow from a cut stem without losing quality in flavor or texture.
• Cos or Romaine is an upright plant with long, narrow leaves that look coarse but are quite tender.

Lettuce vs. Cabbage

Both lettuce and cabbage varieties grow in heads with layers of leaves. However, cabbage tends to be tougher than lettuce because it has lower water content. Cabbage typically has a stronger flavor while lettuce is very mild.

Harvesting Lettuce

The best time of day to harvest is in the morning when the lettuce is still plump and the sun hasn’t caused it to wilt at all. You can harvest cut-and-come-again lettuce types as soon as the outer leaves reach about 6 inches long. Trim off these outer leaves, leaving the inner leaves to continue to mature. If you are growing head lettuce, be sure to harvest before the head starts to elongate. That means it's ready to bolt, and the flavor will suffer. It can be stored in the refrigerator in a plastic bag for up to 10 days. 

How to Grow Lettuce in Pots

Growing lettuce in a container is a good option to help protect it from pests. You also can keep the container in a convenient spot for harvesting. Make sure to check the space requirements for your particular lettuce variety. In general, a container that’s six to 12 inches across should suffice. Make sure it has drainage holes. Unglazed clay is an ideal container material, as it will allow excess soil moisture to escape through its walls.

Pruning

The only pruning maintenance lettuce needs is harvesting its mature leaves. Also, trim off any broken leaves that drag on the ground to prevent them from introducing pests and diseases to the plant.

Propagating Lettuce

Lettuce is commonly grown from seeds. But it also can be regrown from scraps. This won’t provide as large of a harvest as your initial planting, but it is an inexpensive and easy way to get more lettuce. Here’s how:

1. Cut off the bottom of the lettuce, leaving only about an inch of leaves on the base. 
2. Put the base in a shallow dish of water by a sunny window.
3. Change the water every couple of days. You should see some root and leaf growth in about a week.
4. Harvest the leaves in two weeks. At this point, they’ll likely be as large as they will grow and will only degrade from there.

How to Grow Lettuce From Seed

Whether you’re planting in containers or in the ground, make sure the seeds are only lightly covered in soil. Keep the soil evenly moist but not soggy as the seeds germinate, which should take around seven to 10 days. The soil temperature should be at least 40 degrees Fahrenheit and ideally between 55 and 65 degrees Fahrenheit. 

Potting and Repotting Lettuce

A quality all-purpose potting mix is typically fine for lettuce. But a mix marked specifically for lettuce is better, as it usually has components to retain adequate soil moisture. Aim to plant lettuce initially in a container that will accommodate its mature size to avoid having to disturb its roots with repotting.

Overwintering

Lettuce is an annual, so no overwintering is necessary. Be sure to harvest in the fall before freezing temperatures arrive.

Common Pests and Plant Diseases

Lettuce typically doesn’t have any serious pest or disease problems. Common pests that might afflict lettuce include aphids, slugs, and snails, as well as wildlife nibbling on the leaves. Diseases include powdery mildew and downy mildew. Growing lettuce in the environment it likes can help to prevent pest and disease issues.