Growing lettuce is super easy, but there are some things to know that will help you get a more varied and sustained harvest and that can keep you in fresh, tender lettuce all summer — and even past fall frost.
Lettuce is considered a “cool season” crop, which means it prefers cool weather (45-65° F), and most varieties will survive light frosts. It also means that lettuce may “bolt” — or send up a flower stalk and go to seed — if it gets much above 80° F.
For the earliest possible lettuce harvest, start growing lettuce seeds indoors under lights about 4-6 weeks before your last spring frost, and transplant them out 2-3 weeks later (3-4 weeks before last frost). Plant them about ¼” deep in good potting mix. Transplant them out 4-8” apart, depending on variety.
At the time you transplant out your first lettuce seedlings, also direct seed a few more right in the garden, but not too many, or you’ll have too many ready to eat all at once. For a sustained harvest, keep planting a few seeds along the row (or in the bed) every couple of weeks until the daytime highs get above 70° F, at which point you can start seedlings indoors again under your light set-up.
Why indoors? When it gets hot in the middle of the summer, lettuce seeds won’t want to germinate. There are some very good heat-tolerant varieties (Parris Island Cos Romaine, Magenta, Teide, Red Cross, Magenta Summer Crisp, Adriana) that resist bolting when it gets too hot, but even those varieties won’t germinate when it’s hot.
Many other varieties of vegetables don’t germinate well when it gets too warm either, so make use of your seed-starting setup in July and August for germinating and growing lettuce transplants and other seedlings for fall gardening.
Harvest baby lettuce by cutting young leaves off a couple of inches up from the base, letting the plant regrow from the center before harvesting again. This is known a “CCA” harvesting, or “cut-and-come-again”. Many CSA farms use this method of growing lettuce, harvesting down a row each week. Smaller lettuce leaves are very tender and delicious, and if you leave enough lower leaf growing the plant will have enough energy to grow back from its center fairly quickly. I like to grow some of my lettuces to harvest this way, usually a mesclun mix.
Outer Leaves Only
Harvest just the outer leaves of the growing lettuce plants, fairly often. I harvest most of my lettuce this way. Only when the leaves start to get lanky (when the plant starts to think about bolting) do I pull up the whole plant.
Yank Out the Whole Plant
Wait until the plant is pretty good sized, and harvest the entire plant, cutting it off at the base. The root is capable of putting out some more top growth, but it will be slow because you have taken its sunlight-collectors away, so it’s better to pull and compost the root, prepare the soil as a nice fine seedbed again, and replant another seed in the same spot. I usually only harvest this way if the plant is thinking about bolting, or if I’m in a hurry and need a couple of nice big romaines for a potluck Ceasar salad.
Here’s how I do my seeding, which works well for a cold winter/hot summer region. It keeps two people in lots of salad all season. i always use two seeds per hole and thin them if they both sprout, which is insurance against non-germination or hungry birds (if direct seeded):
The hundreds of varieties of lettuce fall into seven basic types, each with its own special qualities and uses. Two are rarely grown in home gardens (Chinese stalk lettuce, and seed oil lettuce) so I won’t cover those.
Crisphead lettuces fold their leaves over into the middle as they mature, forming a dense head. They tend to be the crunchiest of lettuces, but also the lowest in vitamins. Traditional iceberg lettuce is one of these, and after a period of being considered “boring”, is now experiencing a resurgence as chefs rediscover its unique flavor and crunchy bite. Varieties: Great Lakes, Black Seeded Simpson, Red Grenoble, Crystal.
Butterhead lettuces are more tender and silky than crispheads, and their heads are more loose and open. They come in a beautiful selection of colors, and are higher in vitamins and minerals that most crispheads. Varieties: Bibb, Santoro, Buttercrunch, Four Seasons, Speckles, Tom Thumb.
Summercrisp or Batavian lettuce is kind of in between the butterheads and looseleaf lettuces in shape and texture. Varieties: Cherokee, Magenta, Teide, Nevada, Muir (most heat tolerant).
Looseleaf lettuces are tender like butterheads, but reach their large open leaves upward and outward without forming heads. Varieties: Red Sails, Red Velvet, Green Ice, Salad Bowl.
Romaine or “cos” lettuces are generally the highest in vitamins and minerals, and have crunchy stems and semi-crunchy leaves. They also come in a wide variety of colors, sizes and shapes. Varieties: Parris Island, Freckles, Little Gem, Craquerelle Du Midi, Silvia.
“Mesclun” is not actually a type of lettuce, but rather refers to a mixture of lettuces and (sometimes) related greens, that are grown together to produce a beautiful, nutritious salad mix when harvested. The term "mesclun" comes from the French word "mescla", "to mix". Different seed companies have different mixes, based on sweet, tangy, extra-colorful, ethnic traditional or other blends.
In order of heat tolerance and bolt resistance, the best are generally the looseleaf varieties, followed by romaine, summercrisp, butterhead, and crisphead. Search seed catalogs for details.