Whether they're called Buttercrunch, Little Gem, Tennis Ball, Bronze Mignonette, or Freckles Romaine, all salad greens start life as tiny black dots. Six weeks or so down the line, they're a fresh salad on the table. And the crisp, chilly days of early spring are the right time to start planting these tender crops. "Lettuce is one of the easier things to grow," says Charlie Mazza, a horticulturalist at Cornell University. The seeds need rich, well-drained soil (dark and moist, but not puddley), cool weather, and some light. Beyond that, "they are one of the more forgiving plants. They can even grow in a window box," he says.

Growing Season
Lettuce is a cool-weather crop, and seeds can go in the ground about four weeks before the last frost. (If you live in a warm region, you can grow lettuce until the highest daytime temperature remains steadily above 80 degrees.) Check with your local county agent or State Cooperative Extension Office (the numbers are in the "Government" section of the phone book) for planting requirements; their websites often have answers, as well as links to the volunteer-staffed Master Gardener program. The U.S. Department of Agriculture's site, www.gardening.gov, is also full of regional climate and soil information. Plan for your last harvest before it gets too hot. Most lettuce varieties go from seed to salad in 45 to 80 days. And if you sow seed every 8 to 10 days, you should have a constant supply all spring, even in a small space.

Soil
Till the soil well before planting. Because lettuce is one of the first things to go into the ground, the earth will probably be solid and inhospitable to small seeds. You can also use almost any container to grow lettuce. Just make sure it's at least six to eight inches deep and has good drainage.

Seeds
Lettuce seeds are the size of pinpoints, so burying them too deep can make it hard for them to germinate. Check seed-packet labels for instructions. Scatter the seeds directly onto the ground; you will thin the plants as they grow.

Water
Depending on your climate and weather, water a few times a week or every day. Don't let the soil get too dry or the plants will wilt. And don't hose down lettuce until puddles form.

Fertilizer
You won't need a lot of fertilizer (lettuce isn't as demanding of nutrients as flowering plants), but make sure that any fertilizer you use is suitable for edibles. Look for the words "organic mix" on the label, or check with your nursery. Garden compost is a safe alternative.

Thinning
When leaf-lettuce plants are about one inch high, you can begin thinning and eating the lettuce. Use scissors to cut or snap off the shoots. This will prevent the roots of the remaining plants from being disturbed and give the plants room to thrive. To thin head lettuce, simply uproot the immature head. Keep thinning until plants are 4 to 10 inches apart, depending on the variety; head lettuce needs more space so it can form a ball.

Picking
When your lettuce is fully grown (check the information on the seed packet), pick it immediately and enjoy. During the growing season, you can sow new seed almost weekly so there will always be more on the way. When the leaves grow longer than four to six inches, you may find them too tough and bitter. So discard overgrown plants, which will make room for new seedlings.

The Four Categories

Crisphead
The most famous variety (some chefs might say the most infamous) is iceberg, the tight, crunchy head you have probably eaten as a wedge, slathered with Russian dressing. Although iceberg isn't as popular as it used to be, it is still the number-one seller in American super-markets, and there's nothing like it for giving a tuna-salad sandwich some snap.

Growing tip: Of the four types of lettuce, crisphead is the most sensitive to heat. Without the right cool temperatures, the plants won't form the proper tight shape.
Other varieties: Wakefield Crunch and New York.

Butterhead
If crisphead varieties are the tap water of the lettuce world, then butterheads, also known as Bibb lettuces, are the Evian. As the name suggests, their leaves are soft, tender, and slightly richer in flavor.

Harvesting tip: Because their oval leaves are so bruisable, butter-heads are ideal for the home gardener, who can show them more mercy than produce shippers can.
Other varieties: Boston, Little Gem, and Buttercrunch.

Cos
This variety includes that staple of the Caesar salad, romaine. Cos lettuce has a long, upright head and leaves with crunchy spines and a sharp flavor.

Serving tip: Its texture makes Cos an ideal partner for limper, hard-to-fork baby lettuces and greens.
Other varieties: Rouge d'Hiver, Cimmaron, and Paris White.

Loose Leaf
These lettuces branch off from a single stalk. This means you can harvest a few leaves at a time while the plant continues to grow (head lettuce is an all-or-nothing proposition). Most grocery stores now sell bags of mesclun salad consisting of leaf greens, and many gardening catalogs sell mesclun seed packs: You sow the seeds, wait a few weeks, and see what comes up.

Growing tip: Because they don't form a head, loose leafs can tolerate warmer weather better than some of the other families, but they, too, grow bitter in the heat.
Other varieties: Arugula (also known as rocket, and not technically a lettuce), red leaf, frisee, and Black-Seeded Simpson.

Choosing a Crop
For some armchair gardeners, the fun lies in studying seed catalogs. There is also a boundless variety of seeds available to home gardeners through nurseries, hardware stores, and the Internet. Consider the flavor descriptions and growing times when deciding which to plant. Look for heat- or cold-resistant varieties to suit your climate.

Pests
Slugs and snails can make lettuce look like lace, but don't fight them with pesticides. Though slugs love lettuce, they like beer more. Set shallow containers of beer around the garden the slugs will slither in and drown. If necessary, protect lettuce from rabbits, deer, and other animal intruders by using fences, chicken wire, or all-purpose garden fabric ($8 to $30 at Gardener's Supply Company, www.gardeners.com, 888-833-1412).