Grow Lettuce Indoors All Winter

Kathleen Marshall | November 11, 2017

Takeaway: There’s nothing better than biting into a nice, crunchy salad made with homegrown lettuce leaves, but with frost covering the backyard garden, you’re going to need to move production indoors. Luckily, lettuce is one of the easiest crops to grow inside, even if you’re new to indoor gardening. Just follow these simple steps.

Buying fresh salad greens in the winter can be a pretty pricy endeavor. Fortunately, you can easily grow your own indoors, even if you’ve never tried indoor gardening before.

Choosing the Right Variety of Lettuce to Grow Indoors

You might think that lettuce is all the same, but loose-leaf varieties grow best in indoor gardens, especially in colder temperatures. This is important because even though you can control the temperature when you are growing indoors, the less heat you have to add to the grow space, the more economical your growing endeavor will become.

Varieties especially suited for growing indoors include black seeded simpson and tom thumb. Mesclun mixes, arugula, and baby spinach also do well but don’t be afraid of experimenting with other varieties or you might miss out on a special favorite you haven’t discovered yet. Loose-leaf lettuce grows quickly, can produce multiple yields and comes in a variety of colors to create a colorful salad.

Selecting the Right Location

If you can, choose a room that gets lots of natural light, but even if the room you choose has lots of natural light, your plants will need the help of artificial lights.

Lighting isn’t your only consideration when choosing where to grow your lettuce. Choose a room that isn’t too hot or freezing cold. Make sure you have easy access to water, as running from one end of the house to the other transporting water loses its fun-factor quickly.

Easy access to electricity is also important. You don’t want extension cords running through the house to power your supplemental heat or light sources.

Heat and Light Considerations for Growing Lettuce Indoors

To successfully grow lettuce, you’ll need a minimum of 12 hours of light, with 14-16 hours of light being ideal for most plants. If you are relying heavily on windows for some of your lighting needs, you’ll need to rotate your growing containers or your plants will lean towards the light as they grow

Keep in mind there are fewer daylight hours in the winter, so a supplemental lighting source is necessary. A wide array of grow lights will provide full-spectrum lighting, but some of the more advanced systems may seem pricey to novice indoor growers.

To start out your indoor gardening adventures, you can opt for a simple T5 grow light from your neighborhood hydro store. As you gain more experience and confidence in your abilities, you can always upgrade your equipment to match your needs. Make sure your light source is adjustable and keep it 4-6-in. above your plants. As the plants grow, you’ll need to raise the lights.

Most types of lettuce thrive in cooler temperatures and go to seed when it gets hot, but there are several varieties bred to be slow to bolt. Lettuce thrives in temperatures between 60 and 70˚F during the day, and about 10 degrees cooler at night. You can grow lettuce in cooler temperatures than these, but it will grow more slowly.

Picking the Right Medium

A seed-starting mix is ideal to use when you are growing lettuce indoors. It is lightweight, which makes it easy for seedlings to pop through the surface of the soil. A soilless potting mix is also a good choice. You can make your own with equal parts peat moss or coir, vermiculite or perlite, and sand.

Growing containers can be shallow, as lettuce does not have a deep root system. You can use growing trays from your local garden center or even recycle containers from home, like empty yogurt cups or egg cartons.

If you have an assortment of flowerpots or planter boxes, those will work just fine, too. It isn’t necessary for each plant to grow in its own container.

Fill your containers with moist potting mix and you are ready to plant.

Planting Lettuce

Plant your seeds about an inch apart, or about four seeds per pot if you are growing in seed-starting trays. Lettuce seeds are small, but if you sow seeds a little thicker than desired, you can simply pull any excess seedlings.

Once your seeds are in place, cover lightly with potting mix and mist with a spray bottle. It’s important to water gently so you don’t wash away the tiny seeds.

If you have a seed-starting tray, put the cover on it and keep it moist until the seedlings sprout. You can achieve the same effect by covering containers with plastic to create a greenhouse effect.

Moisture from the soil accumulates on the plastic and then drips onto the seeds. Once seeds have germinated, remove the plastic covering.

Fertilize when the first real leaves appear on your plants. I like to use an organic fertilizer that’s diluted by half. Avoid getting fertilizer on the leaves so you don’t burn your plants.

Harvesting Your Indoor Lettuce

You can expect to start enjoying the fruits of your labor within several weeks—in 20-30 days, your lettuce will have grown to about 4-in. tall. To harvest, cut the larger outer leaves. If you cut what you need just above the soil and allow the smaller parts to grow, you can extend your harvest to 2-3 cuttings.

For a continuous harvest all year, sow seeds every two weeks. You might have plans to grow lettuce outside when the weather warms up, but if you continue growing indoors, you won’t have to worry about slugs and rabbits eating your salads. And no one says you can’t do both! Experiment and decide what fits your needs the best.

Growing lettuce indoors is a rewarding project for beginners because it offers quick results with little effort. It’s also an excellent learning opportunity for children.

Once you’ve enjoyed a fresh, homegrown salad in the middle of winter, you may be inspired to try other indoor gardening projects like culinary herbs. Start small and add more as your experience allows.

Read More: Winter Lettuce Production Tips

Written by Kathleen Marshall

Kathleen Marshall has been gardening since she was old enough to hold a shovel. She is a master gardener through the University of Florida and likes to experiment with various types of growing, indoors and out. Her passion is self-reliance. Currently, she resides on a 100-acre homestead with her family, where she works on growing as much of her family's food as possible. Full Bio