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How to Grow Lettuce Indoors (+Easy DIY Steps)

Updated December 13, 2021 by Mark Marino

Growing lettuce indoors is a great way to enjoy fresh salad year-round, provided you have space to grow enough lettuce plants and can fulfill their care needs. It’s easy to grow lettuce indoors because lettuce plants have shallow roots that make them well suited to container planting. An annual plant, lettuce is a member of the daisy family, known botanically as Asteraceae. Many lettuce varieties are rich in nutrients and not only make for a nutritious, but also a most attractive-looking salad. If you want to learn how to grow lettuce indoors, you can learn more about lettuce plants and their care with the following information.

Lettuce Plants Overview

The ancient Egyptians appear to have been the first people to cultivate lettuce plants. From there, growing lettuce as a crop spread to the Mediterranean region. By the 18th century, Europeans had developed many different lettuce types that we continue to enjoy today. With the price of a head of lettuce creeping up in North America and elsewhere, it’s no wonder many people are considering growing lettuce indoors. Moreover, commercially grown lettuce has been vulnerable to bacterial outbreaks involving E.coli. By growing lettuce indoors, you can more effectively control its environment and safety. 

Types of Lettuce to Grow Indoors

There are three main types of lettuce that include leaf lettuce, head lettuce, and romaine or cos lettuce. Within each category, you’ll find various cultivars. Some of the most popularly grown indoor lettuce varieties include:

Romaine Lettuce

Romaine lettuce is a salad bowl staple with its high nutritional content. You may also be able to fit more romaine lettuce plants in your space because of its compact, upright growth habit. Romaine is a favorite lettuce to use in salads, especially Caesar salads, or on sandwiches with its bright green leaves and crunchy ribs.

Iceberg Lettuce

Although lower in nutritional content than other lettuce types, iceberg lettuce is among the most popular cultivars with its mild flavor and rich moisture content. Iceberg makes a great salad base and is also enjoyed on sandwiches, tacos, and more. 

Leaf Lettuce

Leaf lettuce, also known as loose-leaf lettuce, is one of the easiest lettuce plants to grow and harvest. Its leaves are loosely bunched and used most frequently in salads. Many people find that leaf lettuces are the least challenging lettuce plants to grow indoors. 

Growing Lettuce Indoors: Supplies

To grow lettuce indoors successfully, you should gather the following supplies:

  • Lettuce seeds or lettuce seedlings
  • Potting soil
  • Liquid fertilizer 
  • Well draining containers 
  • Grow light (optional) 

How to Plant Lettuce

You can grow lettuce from lettuce seeds or use a seed starting mix. You can also grow lettuce plants with a hydroponic system or in a grow tent. When growing lettuce from seed, prepare your containers. Ensure that each has drainage holes and well-draining potting soil. Plant your lettuce seeds on the top of the soil with only a light dusting of soil cover. The seeds need sunlight in order to germinate. Spray the seeds with a water bottle and ensure they remain moist until germination occurs–usually about 7-10 days after planting. There is no need to rely on a growing plant when seedlings sprout; they prefer cooler temperatures.

How to Care for Indoor Lettuce Plants

Once your seeds have germinated and young plants emerge, rely on the following care tips to promote good indoor growing conditions:

Light

Lettuce plants need full sun to grow well or they’re apt to struggle and remain spindly. Full sun exposure for at least 6 hours a day is ideal. However, 12 hours in a sunny window with full to partial sunlight is ideal. You can also rely on a grow light to ensure your plants get the lighting they need to thrive. 

Water

When growing lettuce indoors, keep the soil evenly moist. Plan to water your lettuce every few days, especially if your home is dry. Water lettuce with tepid or warm water rather than cold. You should also water your lettuce seedlings using a water tray; watering from the ground up will help you prevent downy mildew or other fungal diseases that lettuce can be subject to. 

Soil

Ideally, you should use a soilless growing mix that includes peat moss or coconut coir for planting lettuce. You can then use your potting mix when the seedlings emerge. 

Temperature and Humidity

You can use a spray bottle to lightly mist your soil between waterings. Too much humidity, however, can leave lettuce leaves vulnerable to fungal diseases. Don’t grow lettuce near a heat source. It prefers slightly cooler temperatures that range between 65-70 degrees.

Fertilizer

You can feed lettuce seedlings with a liquid fertilizer diluted to half strength for about three weeks. Opt to feed them once per week. Avoid getting any fertilizer on your lettuce leaves.

Harvesting Lettuce

You can harvest loose leaf and romaine lettuce when they grow leaves that are big enough to use. Harvest the plant’s outer leaves first, allowing the inner leaves more time to grow. Baby lettuce is usually ready for harvesting in about a month from germination. A head of lettuce typically isn’t ready for harvest until 70 days after germination.

After harvesting your lettuce, wash and dry lettuce leaves. You can then store them in an airtight container in your refrigerator for a week or longer depending on their freshness. Or, you can use your freshly harvested lettuce right away.

Uses and Benefits of Lettuce

Lettuce is primarily used as a base for a salad or topping with tomatoes for sandwiches and wraps. As we discussed earlier, the nutritional content of lettuce varies by type. Romaine is regarded as among the lettuce types that are highest in nutrition. Generally speaking, however, you can expect to enjoy certain benefits when eating lettuce. Since it’s made up mostly of water, lettuce boosts our hydration levels. It is also known to support bone strength, support vision, and reduce combat free radicals with its antioxidant properties.

Chef’s tip: Boston Bibb lettuce makes a great low-carb wrap for tacos and sandwiches. Also, cut Romaine lettuce lengthwise and grill cut side down. This makes a nice smoky “wedge” salad.

Indoor Lettuce FAQs

Can you grow lettuce indoors year-round?

Yes, you can grow lettuce year-round. Many indoor gardeners stagger lettuce plantings so they have a steady stream to harvest throughout the year. 

Can you grow lettuce indoors without a grow light?

You can grow lettuce without a grow light if you have a window that receives at least 6 hours of full sun. If you don’t have a sunny window with direct sun, you should use a grow light.