Lettuce is another wonderful springtime crop. It grows well in the cool weather of the spring and it matures relatively quickly. If you really can't wait, you can harvest lettuce before it fully matures for baby salad greens.
So many types of lettuce are available! You can find lettuce in different colors: almost every shade of green, red, and mixtures of red and green. There are varieties that grow in tight heads something like a cabbage, loose heads, or in clusters of leaves. There are upright lettuces like Romaine, and squat lettuces. The textures vary from curly leaves to relatively flat smooth leaves.
For the beginner gardener, here are a few tried-and-true varieties to start with. Here are some good beginner lettuces. They grow easily and have a nice flavor.
Lettuce is most commonly grown from seed directly sown in the garden. It is possible to grow lettuce from transplants, but since lettuce is a fast-maturing crop and the seeds germinate in cooler temperatures, lettuce transplants are not always easy to find at a garden center. I have only really seen transplants for Romaine type lettuce, where you want to grow an entire head of lettuce.
You can start your own lettuce seeds indoors to create your own transplants.
Lettuce seed is planted shallow at only about 1/8th inch deep in the soil. The seed will germinate in soil temperatures as low as 40 degrees, but it does best in soil temperatures in the 60s. Lettuce seed does not germinate at soil temperatures over 75 degrees, though, so it is a true cool season crop.
If you start your lettuce seeds inside, they should grow for 3-4 weeks before hardening off. After 3 to 4 days of hardening off, they are ready to be planted outside and they can withstand a hard freeze (temperatures below 32 degrees.)
Lettuce seeds are tiny and can be difficult for the home gardener to handle. The seed of many of the more popular varieties of lettuce are available as pelleted seed.
Growing lettuce isn't difficult. The seedlings need even watering, cool temperatures, and sunlight. Unlike many other garden vegetables, lettuce can tolerate some shade, although it tends to grow more slowly in the shade.
Lettuce does not require much fertilizer as long as it is grown in good soil containing lots of organic material. A balanced fertilizer (such as 10-10-10) can be applied to the soil before planting at the recommended rate, to ensure all nutrients are available.
The most common pests of the lettuce crop are slugs, snails, and small mammals like squirrels, rabbits, and mice. For slugs and snails, deterrents and traps are available (see this homemade slug trap from Till and Trowel.) For the critters, physical barriers such as fences and cloches work well.
There are two methods of harvesting lettuce. First is simply wait until the lettuce plant is large enough, then pull from the soil. You can also simply cut the lettuce from the root at the soil level using a knife or scissors.
This harvesting method can be used for a mature lettuce plant or when the leaves are small and young for "baby" salad greens.
Another way to harvest is called cut and come again. You harvest the outer and lower leaves of the lettuce as they mature and leave the smaller, younger leaves on the plant to continue growing. You can harvest several times from one plant using this method. It's a nice way to harvest only as much as you need at one time, then come back for more later.
Lettuce grows close to the soil and usually picks up some grit and soil on the leaves. It is always a good idea to wash your lettuce. To wash, you plunge the lettuce in cool or cold water. Agitate it a little to loosen up any soil clinging to the leaves, then let it sit for a few minutes. This will allow the dirt to sink to the bottom. Remove it from the water and whirl it around in a salad spinner to dry it off.
You can do this with the whole plant or you can separate the leaves, or even tear the leaves into bite-sized pieces, for your salad before washing it. Separating it into leaves or bite-sized pieces is the preferred method for lettuce that grows in a head, since it's difficult to get any wayward dirt from the inner layers of a head of lettuce. Difficult to dry off, too.
As your lettuce plants mature, and the weather gets warmer, the plants may start to bolt, meaning they start to grow flower stems to produce seeds. You will notice a stem starting to grow up from the center of the plant. Once this process has started, it's time to harvest the entire plant and your lettuce is done for the season. The lettuce leaves start to take on a more bitter flavor when the plant starts to bolt.
Of course, if you want to collect the lettuce seeds for next year's crop, let the lettuce plant flower and go to seed. You also might be curious to discover what lettuce flowers look like!
Personally, I'd rather free up the space in the garden for another crop.