Pro Tips on Growing Lettuce and Troubleshooting Problems

Growing lettuce is easy. Preparing your planting site and keeping the plants sheltered from strong heat are the most important aspects of growing lettuce. Walk your garden each day to check for problems or pests.


When to plant lettuce?

A soil thermometer is the best tool for gauging when to start planting seeds. Lettuce will grow in cool weather and withstand a light freeze. When the soil temperature has warmed to 45°F (7.2°C) it is time to plant lettuce seed. Another rule of thumb is about 2 – 3 weeks before your last frost.

Lettuce is a successional vegetable in the garden. This means that from your first planting you can sow additional seed every two weeks through the fall. This ensures a steady supply of fresh, mature lettuce in the garden.

In some climates, autumn plantings of lettuce are the most successful. The August heat helps to sprout the seed and then the cool fall season keep the plants from bolting.

Where to plant lettuce?

Lettuce does fine in either full sun or partial shade. When planting during a cool season, full sun is acceptable. If you’re doing successional plantings, keep in mind that full sun during high summer causes lettuce plants to bolt or go to seed. Plan a site that gets some afternoon shade during the heat of summer to avoid overheating your lettuce plants.

Create shade through companion planting lettuces alongside taller plants like kale and broccoli. Brassicas work especially well with lettuce because they add shade, and the lettuce helps to keep the brassica roots cooler.

The soil should be well-draining but not dry out too easily. Dry roots are another way to quickly send lettuce plants to bolt. If your soil is sandy and tends to dry out, add a layer of mulch on top of the soil around the lettuce plants to hold in moisture.

Plan a planting site that helps with potential pest issues. Place your lettuce plants near to or amidst aromatic herbs like fennel and mint to encourage beneficial insects and discourage detrimental insects.

How to plant and thin lettuce?

If planting starts from the store or greenhouse, simply pull back any existing mulch to create a small circle. Work the soil inside the circle with a spade and add some compost to it as you mix. Plant the lettuce, press into place and pull the mulch back up around the base of the plant but not touching it. Space your plants 4-15 inches apart depending on variety and water your starts thoroughly.

If planting seeds, rake back all existing mulch. Loosen the soil if necessary and then scatter your lettuce seed over the area. Be generous with the seed, it’s easier to thin then to try and fill empty spaces. Cover the seed with ¼ inch of compost that will feed the plants and water them in thoroughly.

When starts reach between 1 and 2 inches tall, you can thin them. Loose leaf varieties of lettuce don’t need much thinning, a spacing of between 3 and 4 inches is just fine. The tighter the head of lettuce, the more room it requires. Crisp heading varieties like Iceberg take up to 15 inches of space.

Pest problems and solutions

Because it is often grown in the spring and fall, slugs and snails are common pests in lettuce crops. If you live in a wet climate, mulch can harbor slug eggs and compound the problem so consider plastic soil covers or no cover at all. Making habitat for snakes in the garden goes a long way toward reducing slug populations.

Aphids start to attack lettuce plants when the weather warms and the lettuces become vulnerable. Attract predatory insects like ladybugs to balance out aphid populations. With a healthy diverse ecosystem, often aphids clear up on their own.

Lettuce plants are particularly attractive to caterpillars. They fly into the garden and lay their eggs in the fall as moths. Then they hatch in the spring and devour your young leaves before they’re big enough to eat. Install birdhouses around the garden to reduce moth populations. Companion planting will help deter moths and attract beneficial insects. Some excellent companions include:

  • Sage
  • Lavender
  • Basil
  • Fennel
  • Mint
  • Lemon Balm
  • Marigold
  • Geranium
  • Cilantro

How to harvest lettuce?

Generally, there are two types of lettuce. Loose-leaf lettuces and greens often called ‘cut and come again’ like arugula, mustards, or red and green leaf lettuces, and then heading lettuces. The name ‘cut and come again’ refers to the fact that you can take leaves from them all year long without killing the plant.

Harvest the outer or lower leaves of these greens, leaving the center of the plant intact so it can grow new leaves. Green like arugula can be cut almost to the soil surface and they will bounce back. Leafy lettuces tend to grow up the main stem, and the leaves that are harvested are the lowest or the outermost.

Heading lettuces work more like cabbages in that you’ll be allowing them to fully mature before picking the whole thing. Lettuce heads should be harvest when they are firm to the touch and do not collapse when squeezed lightly.

How to propagate lettuce?

Lettuce is most commonly propagated by seed. Instead of harvesting all of your plants, allow a couple of them to go to seed in the fall. Depending on your climate, some will overwinter and then seed the following spring. Either way, you’ll see a bloom of little flowers followed by the development of small seeds with dandelion-like parachutes attached to each bundle.

Harvest the seed when it is fully mature but before it blows away in the wind. Once the hair-like parachutes develop they are likely mature enough. You can place a mesh bag over the whole bloom to catch the falling seeds if you don’t want to worry about timing.

Take seeds from your best-performing plants, not plants that bolt prematurely. It is tempting to save seed from bolting lettuces, and there’s nothing wrong with the seed. The fact that it bolted suggests that it may not be as suitable for your climate as the plants that gave good leaf. Also avoid saving seed from hybrid varieties of lettuce as their offspring will not be true to type, meaning you won’t get the same plants the following year.

Gardeners can also propagate heading lettuces by the stems. After eating a head of lettuce, you are often left with a 2-3 inch long stem. Place this is a jar of water for a week or two. Roots will form on the bottom and new leaves will begin to emerge. Once it has roots, it can be planted in the ground.

How to control bolting?

Bolting is a common problem with lettuce in the garden. This occurs when the plant is under stress and decides to quickly go to seed rather than produce nice edible leaves for eating. Days of intense heat and sun can cause whole lettuce crops to bolt, which is why afternoon shade is extremely beneficial in climates with warm summers.

If a lettuce plant gets too dry, it will bolt. Regular watering and checking the soil each day for moisture is important for garden success. If the soil feels dry at a fingers’ depth, it should be watered.

Some varieties will do better in your garden than others. If bolting is a problem with one variety, swap it out with something different next year. Finding the right varieties and saving seed from the good ones each year will help develop a lettuce that is well adapted to your specific garden environment.

How to plant lettuce in a pot?

Lettuce is a perfect vegetable to grow in containers. Many people grow it on balconies and patios beautifully. The most important thing is to make sure the soil and container drain well. Lettuce needs moisture but doesn’t like its feet wet.

Cut and come again varieties are especially rewarding in container gardens because of the long harvest. Rather than wait for a mature head; cut leaves from your lettuces all year long.