should lettuce be started indoors

Lettuce is a fast-growing cool-season crop for spring and fall that is attractive in both vegetable and ornamental gardens and is suited to container gardening as well. If you want to grow lettuce in your garden, here’s what you need to know.

You can also download my How Do I Grow Lettuce? one-sheet and keep the free resource handy for your reference.

Where, When and How to Plant Lettuce

The secret to sweet, tender lettuce is fast growth. So start with fertile, well-drained soil. Before planting, amend the first few inches of garden soil with a generous addition of compost to improve soil tilth, and add an organic source of nitrogen, such as blood meal or cottonseed meal.

Lettuce grows best in an area that gets full sun, but it does tolerate shade, so that makes lettuce a great candidate for companion planting with taller crops. In fact, in warmer months, a little shade can stall bolting — that’s what it’s called when a lettuce plant sends up a flower stem and the leaves become bitter.

The ideal soil pH range for lettuce, like many vegetables, is between 6.5 and 7.0. If you are establishing a new planting bed or suspect the pH is off in your garden, getting a soil test now can prevent frustration later. The test results will not only give you an idea of how to amend the pH, but will also let you know which nutrients are deficient.

Lettuce seeds will germinate in one to two weeks in soil between 40 and 75 degrees, but between 40 and 60 will yield the best results. To measure the temperature beneath the soil surface, all it takes is an inexpensive soil thermometer. To learn the ideal soil temperature for germinating the most common vegetable seeds, you can download my Online Gardening Academy™ Optimal Soil Temperature Range chart, a free resource.

Lettuce may be sown directly into the garden under a fine layer of soil after the last hard frost. Space seeds with a foot between rows and 8 inches between plants, give or take depending on the variety. (Refer to the seed packet for variety-specific guidance.) If you intend to harvest the lettuce as baby greens, the seeds may be sown even closer together.

To grow lettuce in containers, use quality outdoor potting mix. (Garden soil is heavier than potting soil, and will not drain adequately in a pot.)

For a jumpstart on the spring garden, start lettuce seeds indoors 3 to 4 weeks before your area’s last hard frost — which is around 28 degrees overnight. Some varieties, especially iceberg-type lettuces, can be started indoors even earlier, about 8 weeks before the last frost, or can be direct sown four weeks before the last frost.

For continuous harvests, stagger plantings every two weeks.

Starting indoors and planting out as soon as possible is recommended to get as much of a harvest from lettuce plants as you can before they bolt. Once bolted, plants should be pulled out to make room to grow something else.

For a fall crop, plant seeds or transplants into the garden about six weeks before the first frost.

Lettuce thrives in temperatures between 45 and 80 degrees and is a great candidate for extending the growing season. To grow lettuce even earlier in spring or even later in fall, plants can go inside a cold frame or under row cover or shade cloth.

The only hard thing about growing lettuce is narrowing down your choices. There are countless varieties of taste, color and shape.

Some lettuce is grown for leaves as a cut-and-come-again crop. Other lettuce is grown for whole heads, and heads can also regrow if given enough time before bolting or hard frost.

There are four main categories of lettuce: iceberg, butter, romaine and loose-leaf.

Romaine lettuces, also called cos, grow tall heads with ribbed, crisp leaves. They are a popular choice because they are heat tolerant. In the kitchen, romaine hearts can be chopped up for salad and the outer leaves can be used in place of tortillas or bread for wraps or buns.

A few examples: Forellenschluss is an attractive heirloom romaine that’s green with burgundy spots. Aerostar is a mid-size dark green romaine with superior disease resistance. Tantan and Intred are examples of “baby romaine” because, at 6 to 8 inches, they are shorter than most varieties. Cimmaron is a red-bronze romaine that dates back to the 1700s and is incredibly resistant to bolting. Breen is more bronze than red, and short, grown for small heads or to cut and come again.

Iceberg lettuces, also known as crisphead, are heat sensitive and therefore best grown in northern states. The green, spherical heads resemble cabbage and are crunchy and mild-flavored. The warmer the growing environment, and looser the head of lettuce will be. This is the lettuce used in wedge salad, but also popular in chopped salad and bags of mixed lettuce.

Saladin is bolt resistant with tight, flavorful heads. Igloo is heat resistant and may be planted in spring, summer and fall. Crispino performs well even when grown in the warm and humid conditions that are challenging for many iceberg varieties. Ithaca is an open-pollinated iceberg lettuce developed at Cornell University in Ithaca, New York, that is slow to bolt. Iceberg A is an heirloom introduced in 1894 that is suited to cooler climates and is especially crisp.

Butter lettuces, also known as butterhead, bibb or Boston lettuce, have small, roundish heads that are looser than a head of iceberg lettuce. The leaves are also quite sweeter — even buttery.

Buttercrunch is so named for its buttery flavor and its texture, and it tolerates heat. Yugoslavian Red has red leaves with green centers and a mild flavor. Grandma Hadley’s is green with purple-tinged edges. Bunte Forellenschluss is apple green with maroon splotches. Red Sails, Dazzle and Flashy Trout’s Back are each good options for a splash of color.

Loose-leaf lettuces grow fast and can be harvested continuously, making them a favorite among gardeners.

Amish Deer Tongue is a very productive lettuce with pointy, dark green leaves. Australian Yellow Leaf is a chartreuse-colored heirloom that is slow to bolt. Oakleaf has medium green leaves and is compact and also slow-bolting. Flame, introduced by Harris Moran in 1988, is bright red and early to mature. Lollo Rossa is compact with a rosette shape and curled purple-red leaves.

Salanova is a group of proprietary lettuce varieties from Johnny’s Selected Seeds that can be grown either in-ground or hydroponically. They offer resistance to both downy mildew and the Nasonovia ribisnigri aphid. Salanova Green Butter has dense rosettes and thin, supple leaves. Salanova Red Batavia is compact and upright with leaves that are green at the base and purple-ish at the tips. Salanova Red Oakleaf is a deep and shiny red with compact heads.

Lettuce has shallow roots, so water consistently — especially on hot days — to provide moist but not wet soil. A 2-inch layer of organic mulch such as shredded leaves or arborist wood chips will help maintain that moisture and protect your plants.

If lettuce grows in dry soil, it can become irreversibly bitter.

How to Grow Lettuce From Seed Indoors & Harvest in One Month! | LucasGrowsBest

FAQ

Should I start lettuce inside or outside?

Lettuce seeds can be sown outdoors as soon as the soil is workable. Soil temperature of 50-65ºF is the optimal range.

What month should I start lettuce?

Planting lettuce in a home garden

Planting: Sow leaf or butterhead types as soon as soil can be worked in the spring, or in late summer. Crisphead and cos (Romain) types may be transplanted in early spring and fall. Tolerates partial shade (4-6 hours of direct light/day) but grows well with full sun in spring and fall.

Can I start romaine lettuce indoors?

• Best Time: Romaine lettuce thrives in cool temperatures (60°F to 70°F). You can start seeds indoors 2-3 months before the last frost for a spring harvest, or start them in the fall for a winter harvest. 

• Light: Provide 6-8 hours of bright, indirect light daily, either from a sunny windowsill or with the help of grow lights. 

• Temperature: Maintain temperatures between 65-75°F (18-23°C). 

• Humidity: Aim for 50-80% humidity. 

• Soil: Use a well-draining potting mix rich in organic matter. 

Should you plant lettuce seeds indoors?

Planting lettuce seeds indoors allows for better control of growing conditions, leading to healthier plants and an earlier harvest. Transplanting seedlings outdoors after the risk of frost ensures they thrive in optimal conditions. What are the best lettuce varieties for indoor growing?

When should I start lettuce indoors?

Optimal Timing: Start lettuce seeds indoors 4-6 weeks before the last frost date to maximize early harvest potential. Challenges to Consider: Be mindful of space limitations and lighting requirements to ensure successful indoor lettuce cultivation. Should I Start Lettuce Indoors?

Why should you start lettuce indoors?

Controlled Environment: Starting lettuce indoors allows you to manage temperature and light, leading to quicker germination and healthier plants. Pest Protection: Indoor cultivation minimizes exposure to pests and diseases, enhancing seedling success.

How long does it take to grow lettuce indoors?

It should take a week to 10 days for the seeds to begin sprouting. After the plants are an inch or two tall, thin them to where there’s an inch of space between each plant. You’ll continue to care for them as they grow from this point. There’s also another unique way to grow lettuce indoors.

Can you grow lettuce indoors under lights?

If you lack sunny windows, you might want to consider growing lettuce indoors under lights instead, either fluorescent or LED fixtures with reflectors. Light fixtures with two to four bulbs will work best and don’t necessarily need to be labeled as grow lights to be effective.

Can you grow butter lettuce indoors?

The loose-leaf type works best for indoor gardening, since its plants can thrive when set close together, while other varieties may not. For instance, growing butter lettuce indoors would require more space. But, if you give such a plant its own pot, you might be able to bring it to a head!