How to Grow Lettuce
I wanted to expand the growing season in my garden by adding cool season vegetables in the spring and the fall. Lettuce was the first thing that came to mind but which kind? There are so many to choose from.
What is Lettuce?
Lettuce (Lactuca sativa) is an annual plant that is grown mainly for its leaves but in some parts of the world, for its stems and seeds. It is thought that the Egyptians were the first to cultivate lettuce, developing it from a local weed that was used for its oily seeds. From Egypt, it spread to Greece and then to Rome. It wasn’t until the Middle Ages that Europeans began to hybridize it and create the many varieties that are known today. The exception to this is stem lettuce (L. sativa var. angustana) which was developed in China. It used in Asian cooking.
There are four main types of lettuce:
- Leaf or bunching lettuce has loosely grouped leaves and does not form a head. It is used in salads.
- Romaine or Cos lettuce grows upright forming tightly packed narrow heads. You will often find it in Caesar salads.
- Iceberg or Cripshead lettuce is the classic head forming lettuce and is the most popular lettuce in the US.
- Butterhead, also known as Boston or Bibb lettuce. It has a looser head than iceberg. The flavor is sweeter and the leaves are tender rather than crisp.
Three lesser known lettuces, at least here in the US are:
- Summercrisp, also known as Batavian or French crisp. It’s appearance is midway between iceberg and leaf lettuce. The heads are larger and the plants are more bolt-resistant.
- Stem lettuce is grown for its seedstalk rather than its leaves. As noted above, it’s used in Asian cooking.
- Oilseed lettuce is grown for its large seed from which an oil that is used in cooking is produced. It has fewer leaves and bolts more quickly than the other kinds of lettuce.
How to Grow Lettuce
Lettuce requires cool weather to grow. Temperatures above 80⁰F cause it to bolt which means that it flowers then produces seeds then dies. The leaves become bitter when the plants bolt. The plants will freeze below 32⁰F. Their ideal temperature range is 45⁰F to 65⁰F. You can extend their growing season by growing them where taller plants will shade them. Lettuce also grows well in containers if you have limited space or no yard to garden in.
Prepare your garden by raking the soil to loosen it. Large clods of soil will prevent the seedlings from growing. Sow the seeds 4 weeks before your last frost in the spring or 4 to 8 weeks before your first frost in the fall. Seeds should be sown ¼ inch apart and ½ inch deep in rows 12 to 15 inches apart. The soil temperature in the spring should be at least 35⁰F. Germination will occur within 6 to 12 days. When your plants have 4 leaves, you can thin them. Proper spacing for leaf lettuce is 4 inches apart, for Romaine, 8 inches apart and for head lettuce, 16 inches apart.
While they are growing, make sure your lettuce gets at least 1 inch of water each week. A thick layer of mulch will keep your plants from drying out in between waterings. Lettuce needs lots of nitrogen. You can side dress your plantings with compost and fish emulsion once or twice during the growing season. A slow release fertilizer can be used instead if you prefer.
How to Harvest Lettuce
No matter which kind you grow, harvest your lettuce in the morning when it is most crisp. You can store in your refrigerator if you aren’t going to use it right away.
Leaf lettuce is usually harvested by cutting off the leaves from the outsides of the plants, leaving the growth tip or bud in the middle to produce more leaves. You can also cut off the plant at the base to harvest all of the leaves at once. This is usually done at the end of the season to prevent the plant from bolting in the hot summer weather or freezing in the cold of late autumn or early winter.
Romaine lettuce is harvested after its characteristic rib forms and the plants have formed their upright clump.
Bibb lettuce can be harvested either by picking the outer leaves like leaf lettuce or you can wait until the heads have formed and harvest the entire plant by cutting it off at the soil line. The heads should be 6 to 8 inches across when they are ready for harvest.
Iceberg lettuce can also be harvested either by using only the outer leaves or by waiting until the heads have formed. The heads are ready for harvest when they feel firm when lightly pressed.
How to Store Lettuce
Lettuce can be stored in a loose plastic bag in your refrigerator for up to ten days. Avoid storing it with fruits that give off ethylene gas such as apples, pears and bananas. Ethylene gas is a ripening agent. Exposed to it, your lettuce will wilt and then rot.
© 2018 Caren White