How to Grow Lettuce Indoors

By the Countertop Harvest team · Last updated October 20, 2026 · How we choose products

Salad greens are among the easiest food crops to grow inside. The University of Tennessee says leafy crops are simpler and faster to grow than fruiting crops and need less light (UT Extension), and the University of Vermont points out that greens are one crop you can grow year-round indoors (UVM Extension). Lettuce grown as baby greens is the quickest route: Maryland Extension puts baby greens at 4 to 6 inches tall, 21 to 40 days after sowing (UMD Extension). This guide covers a windowsill tray, a grow light setup and a smart garden, plus how to cut and come again.

Light

Vermont suggests a sunny spot right in front of a south or west window, away from cold drafts and hot air from radiators (UVM Extension), and gives 10 to 12 hours of light a day as the target (UVM Extension). Maryland, writing about greens under lights, aims for about 16 hours of total light a day with lights typically 6 to 12 inches above the leaves (UMD Extension). Maryland also notes that lettuce grows acceptably well with less than ideal light (UMD Extension), which is good news for winter kitchens.

For lights-only growing, Tennessee estimates that Bibb lettuce needs about 1,400 footcandles if lit for 16 hours a day, and baby leafy crops about 1,000 (UT Extension). Most of us won't measure footcandles, but the point is that a weak desk lamp isn't enough. Vermont's rule of thumb is that leggy or yellowing seedlings need more light, from a closer lamp or longer hours (UVM Extension). Our grow lights under $50 guide lists small fixtures.

Containers and mix

Vermont uses a rectangular window box in front of a window, or a group of small pots, filled with moistened light potting mix or seed starter (UVM Extension). Maryland says to use any lightweight soilless mix and to avoid garden soil, which is too dense for indoor containers (UMD Extension). Any container needs drainage holes and a tray underneath.

Sowing

1. Scatter seed on moist mix and cover lightly according to the packet, then mist with a spray bottle (UVM Extension).
2. Cover to hold moisture. Vermont uses a clear cover such as a cut soda bottle or food wrap, and vents it if water collects (UVM Extension). Remove the cover once seedlings appear (UVM Extension).
3. Thin as they grow. Maryland thins baby greens to about 2 inches apart (UMD Extension), and Vermont adds the thinnings to salads (UVM Extension).

For seed, a loose-leaf mix is the most forgiving choice for cutting young. We like Salad Bowl Blend leaf lettuce seeds for cut-and-come-again trays, and Little Gem mini romaine seeds if you'd like small heads. Both link to Botanical Interests.

Temperature

Lettuce is a cool-season crop. Cornell's guide to home hydroponics for leafy greens explains that bolting, the early growth of a flower stalk, is usually caused by high air temperature, and keeps air below 80°F to prevent it (Cornell guide). Cornell also cites commercial germination at 68°F with 75°F days and 65°F nights after germination, while noting that home growers don't need those exact numbers (Cornell guide). A spot away from the oven and heat vents keeps it happy.

Cut and come again

Maryland cuts baby greens when they reach 4 to 6 inches and says they will regrow for 1 to 2 more harvests (UMD Extension). Vermont harvests once plants are several inches tall by cutting the outer leaves with sharp scissors, leaving the inner leaves to keep growing (UVM Extension). For a steady supply, Vermont replants each container after it has been fully harvested (UVM Extension). We start a new tray every couple of weeks so one is always ready.

Growing lettuce in a smart garden

A countertop smart garden is another way to grow a small salad crop with less fuss over light. Click & Grow sells pre-seeded green lettuce pods for its gardens (Click & Grow), and the Smart Garden 3 is one of the compact models we look at in our Click & Grow spotlight. If you'd like to compare, here are the Click & Grow Smart Garden 3 and the Click & Grow green lettuce pods. Our guides to the best smart garden for a small kitchen and smart garden vs. windowsill compare options, including whether a smart garden is worth it compared with a tray and a light.

In hydroponic systems, Tennessee notes that hydroponic fertilizers differ from soil fertilizers and are made to dissolve completely in water (UT Extension), so use the nutrients made for your system. Our guide to hydroponic nutrients explains the basics.

Common problems

Tall, pale seedlings

Too little light (UVM Extension). Move the light closer or extend its hours.

Brown, crispy leaf edges

Cornell calls this tip burn and found it in small, enclosed setups pushed to high light, with air from a fan reducing it (Cornell guide). A little air movement helps.

Bitter leaves and a central stalk

That is bolting, which Cornell links to warm air (Cornell guide). Move the tray somewhere cooler and sow again.

For even faster greens, see microgreens on your counter and sprouts in a jar. You can also find a guide by plant.

Sources

• University of Vermont Extension: Growing greens in winter (2023)
• University of Maryland Extension: Growing microgreens and baby greens indoors (revised 2026)
• University of Tennessee Extension W 1288-B: Small-space indoor food production (PDF)
• Cornell University (blogs.cornell.edu): Guide to home hydroponics for leafy greens (PDF, 2020)
• Click & Grow product page: Green lettuce plant pods

All sources accessed October 20, 2026. This guide is about growing lettuce and salad greens indoors.

Frequently asked questions

How long does lettuce take to grow indoors?

University of Maryland Extension says baby greens reach 4 to 6 inches about 21 to 40 days after sowing, and mature greens take 40 to 60 days.

How much light does indoor lettuce need?

University of Vermont Extension suggests a south or west window and 10 to 12 hours of light a day. Maryland Extension aims for about 16 hours under grow lights set 6 to 12 inches above the leaves, and notes lettuce tolerates less than ideal light.

Will lettuce regrow after cutting?

Yes. Maryland Extension says baby greens cut at 4 to 6 inches regrow for 1 to 2 more harvests. Vermont cuts outer leaves and leaves the center to keep growing.

Why is my indoor lettuce bitter?

It is probably bolting. Cornell's home hydroponics guide links bolting to high air temperature and suggests keeping air below 80°F.

Can I grow lettuce in a smart garden?

Yes. Click & Grow sells pre-seeded green lettuce pods for its countertop smart gardens, such as the Smart Garden 3.