There are hundreds of varieties of lettuce (Lactuca sativa) you can grow, 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 grow very 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 regarded as a cool-season vegetable, and in most home gardens it is planted in the early spring and harvested in late spring to early summer, then it is discarded in favor of other vegetables for the middle of the summer. Some gardeners may replant a second crop of lettuce as the days grow cooler in fall, but most do not grow lettuce at all in the mid-summer period, focusing instead on warm-season vegetables. Savvy gardeners may plant lettuce among other warm-season vegetables, such as tomatoes, so that by the time the lettuce is finished in early summer, the warm-season vegetables are beginning to take over the garden space.
|Botanical Name||Lactuca sativa|
|Common Name||Lettuce, garden lettuce|
|Mature Size||6 to 12 inches tall and wide|
|Sun Exposure||Full sun to part shade|
|Soil Type||Rich, well-drained|
|Soil pH||Slightly acidic to neutral (6.0 to 6.5)|
|Flower Color||Flowers not showy|
Lettuce is a cool season crop and is best grown in either spring or fall when temperatures do not go to extremes. However, even though lettuce likes to grow during cool, damp days, lettuce seed germinates best in temperature around 70 degrees Fahrenheit. This means you should start early-spring plantings in the garden with seedlings, rather than seed. If lettuce seed is put in the ground while it is still cold and wet, the seed will simply rot. You can always start seed indoors and then transplant the seedlings when all danger of frost has passed.
Lettuce is ideal for succession planting because it matures rapidly and can be planted quite closely. Choosing seasonal varieties will make it easier to keep the succession going. Lettuce can even be grown in containers or used as a decorative border. Just be aware that some animals love lettuce as much as we do.
Lettuce seeds need light to germinate, so barely cover the seed with soil, and keep it moist. Lettuce is a fast grower. It is ready to transplant when several sets of leaves have developed. Don’t let the seedlings get too large before planting them out, or they will bolt to seed the first chance they get.
Plant lettuce in full sun, ideally where it will receive six hours of sunlight per day. It will also grow in part-sun locations.
Lettuce likes a soil rich in organic matter, such as compost or composted manure. This is one crop where extra nitrogen can't hurt, since all you want from the plant is the leaf. Amend your soil before planting, and side dress again mid-season.
Even more than rich soil, salad greens need regular water. If the plants are allowed to remain dry for prolonged periods, especially in warm temperatures, they will turn bitter, the leaves may get sun scorched, and the plants will eventually go to seed. However, don't keep the area persistently damp or use mulch, which invites slugs.
Temperature and Humidity
Lettuce grows best in a temperature range of about 45 to 75 degrees Fahrenheit. Hotter weather makes the leaves bitter.
Growing lettuce in soil that is rich in organic matter will give it most of the nutrients it needs. But it never hurts to supplement with an organic fertilizer like fish emulsion once every two weeks. Dilute the fish emulsion to half-strength, and apply it to the soil rather than the leaves.
There are literally hundreds of lettuce varieties available, although some vary only slightly in size or days to harvest. 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.
- Ithaca: A good choice for fall crops; heat can cause the heads to be looser; resistant to bolting; 70 days to maturity
- Summertime: Large heads slow to bolt in the summer heat, while the heads are forming; frilly leaves resist tip burn; 70 days to maturity
Butterhead also forms a head, but the texture is more soft and pliable with less distinct veins compared to crisphead.
- Bibb: An heirloom lettuce that has remained popular over the years; tender texture; 50 to 60 days to maturity
- Buttercrunch: An American cousin of bibb, but more tolerant of hot weather; 65 days to maturity
- Marvel of Four Seasons: A popular European variety having green leaves tipped with red; can be planted late in spring as well as late in summer and fall; not quite four seasons, but very close; 68 days to maturity
Looseleaf forms a kind of bunch instead of a head. Looseleaf lettuce resprouts from a cut stem without losing quality in flavor or texture.
- Salad Bowl: An All America Winner; easy to grow and fairly heat-resistant; also a red salad bowl variety; 60 days to maturity
- Lollo Bionda: A frilled-edge Italian lettuce that is easy to grow and has a long harvest period; Lollo Rossa is its red cousin; 48 days to maturity
- Oakleaf: Includes many varieties; grows in a rosette and works well as a cut-and-come-again type' 45 to 55 days to maturity
Cos or Romaine is an upright plant with long, narrow leaves that look coarse but are actually quite tender.
- Rouge d'hiver: A red-leafed romaine with a good cold-tolerance; also performs well in spring and summer, making it ideal for succession planting; 60 days to maturity
- Little Gem mini romaine: An English heirloom that grows to only 5 to 6 inches with the crisp texture and the romaine flavor of its big brother; 56 days to maturity
Mesclun: A mixture of greens; typically harvested while young, so succession planning is essential; about a row foot is needed for a salad; most are cut-and-come-again varieties (cut about 1 inch above the ground with scissors to keep it growing); 35 to 45 days to maturity
You can harvest cut-and-come-again lettuce types as soon as the outer leaves reach about 6 inches long. 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.
For the longest harvest, direct seed or transplant every 7 to 10 days. When direct seeding, seeds can either be broadcast and planted in wide rows or spaced 8 to 12 inches apart. Spacing is best if you want it to mature into heads.
If you really hate the idea of living without fresh lettuce during the growing season, there are a few tricks you can try:
Choose the Right Lettuce Variety
First, choose leaf varieties rather than head-forming lettuces. You can start harvesting leaf lettuces as soon as the outer leaves reach about 4 to 6 inches in height. If you cut just these outer leaves, the remaining center leaves can continue growing. Not only do you get to start harvesting early, but cutting like this tends to shock the lettuce plant, preventing it from thinking it has matured and is ready to bolt and go to seed.
Head-lettuces, on the other hand, take a while to develop mature heads, and they sometimes bolt even before decent edible heads can form. Leaf lettuces are a much better choice for continued production.
Some varieties perform better in warm weather than others. Try varieties like Jericho, Parris Island, Red Sails, or Black-Seeded Simpson to stretch your lettuce harvest into warmer months.
Harvest Leaf Lettuce Frequently
If you keep lettuce leaves cropped short, the plants will continue to produce new leaves well into the summer. Allowing leaves to become large and mature signals the plant to send up seed bolts, which is the point where it will no longer be edible. Keep your leaf lettuce cropped short, even if it means discarding some leaves because there is more than you can eat.
Provide Some Shade
Plant your lettuce in the shade of taller plants, like tomatoes, corn, or even vining crops like cucumbers and squash. You can do this when you first start seeding in the spring, or wherever there are bare spots in the garden to fill. Lettuce needs more sun in the cool spring than it does in summer, and positioning lettuce plants around taller plants, such as tomatoes, will provide full sun in spring while the tomatoes are still short, but will offer relief from the intense summer sun.
Sun cloth suspended above the lettuce plants on poles can also help shade the plants and delay their bolting impulse.
Keep Lettuce Plants Well Watered
Regular watering makes plants very forgiving of high temperatures. The evaporation of water from soil provides natural cooling. Water your lettuce plants every day—and even more often if it is extremely hot and dry. The lettuce leaves are mostly water and will desiccate and wilt in strong sunlight and dry soil. Lettuce roots tend to be shallow, so frequent watering is more important than deep watering.
If all else fails and it looks like your lettuce plants are ready to bolt, dig them out of the ground and replant them. As with "cut and come again" harvesting, this is a shock to the plant's system and it will once again focus on growing roots and delay setting seed. Don't keep them out of the ground or allow the plants to dry out—just the act of lifting them and immediately replanting is enough of a shock.
Growing Lettuce in Summer
The early-season planting of lettuce can be harvested into early summer if you follow the above tips, but eventually, it will surrender to genetics and bolt with flower shoots. If you want to have lettuce to harvest in late summer, you will probably have to plant a second crop in early summer. Lettuce seed can be difficult to sprout in warm, dry conditions. Try this trick to get them going:
- Find a somewhat shady spot in your garden and give it a deep soaking of water. Lay a board over the damp soil. The board should be at least as large as your intended planting area.
- Periodically lift the board and re-soak the soil for another two to three days. This should lower the temperature of the soil.
- Plant your lettuce seeds in the prepared area and water them in well. Replace the board over the seeded ground.
- Lift the board and water every day until you see signs of germination, at which time you can remove the board. It should take about 7 to 10 days for the lettuce seeds to sprout. Keep watering whenever the soil dries out. This can mean watering more than once a day, while the seedlings are tiny.
Once the plants are a few inches tall and ready to start harvesting, they should not need a great deal of additional water.
Finally, keep your lettuce seeds handy for a fall planting, when growing conditions are once again perfect for lettuce plants, and the growing is easy. Leaf lettuces grow quickly, and within a few weeks of cool fall weather, you can have some of the tastiest lettuce of the year.