How to Grow Crisp, Fresh Lettuce Indoors All Year Round

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Growing lettuce indoors is a great way to enjoy fresh, flavorful leaves year-round. Indoor lettuce is low maintenance and an ideal choice for indoor gardening.

Growing lettuce indoors is easy, makes fresh greens readily available, and encourages their inclusion in meals. Lettuce is low in calories and fat and is a good source of dietary fiber, vitamins A and C, folate, and iron. Successive plantings of leaf lettuce can ensure a continuous supply.

Table of Contents

Table of Contents 

Grow Lettuce Indoors – Choices

All lettuce cultivars are self-pollinated, non-hybrid, pure lines. There are no hybrid lettuces because lettuce self-pollinates using small flowers that produce a single seed per flower. Botanically, there are four types of lettuce (Lactuca sativa):

1. Celtuce lettuce (L. sativa var. augustana) is grown mainly for its juicy stem, but the whole plant is edible. Most popular in Asia.
2. Head lettuce (L. sativa var. capitata) with leaves folded into a compact, crispy head
3. Leaf Lettuce (L. sativa var. crispa), with a rosette of leaves that may be buttery, curled, smooth-edged, or oak-leaved in shape. Some even from mini heads.
4. Romaine lettuce (L. sativa var. longifolia). Also called Cos lettuce and offers conical-shaped leaves that form a tall, oblong, loose head.

Within each botanical group, there are several cultivars to choose from. Leaf lettuce is a favorite indoor choice as the group provides various colors, flavors, and textures for indoor growing.

This does not mean that Romaine lettuce or Iceberg lettuce can’t be grown indoors, but most indoor vegetable gardeners prefer a shorter turnaround time. Most cooks prefer plants they can readily harvest, adding fresh lettuce to their salad bowl. 

Later in the article, I cover my suggestions for the nine best lettuces for growing indoors. But first, let’s review some how-tos for growing lettuce indoors.

While growing lettuce is easy, there are some basic requirements to ensure they thrive indoors. Check out my Growing Lettuce in Containers article for general guidance.

A Quick Step-by-Step Guide to Growing Lettuce Indoors

Step 1 – Choose a Growing Location

Choose a location that provides enough light. Lettuce needs at least three to five hours of indirect sunlight daily, so choose a spot near a sunny window. I do this first because the choice of location informs my container choice to grow lettuce indoors.

A rectangular pot will work well if you use a sunny windowsill to grow lettuce. Ensure that most of the sun is in the morning and afternoon to avoid the plant getting too hot. A west- or east-facing window will ensure proper sunlight for growing lettuce indoors.

If you like technology, several apps and lighting options can help you keep indoor lettuce plants. These manage moisture levels, grow lights, and give watering reminders. In the right setting, they display well, allowing you to grow lettuce indoors and add vibrancy to the setting.

Grow lights allow you to position your growing container or tower where you like, irrespective of the sun’s position. Several commercial growers use disused underground parking areas to plant lettuce indoors in modular towers using grow lights as their sole lighting source.

Using a colored grow light and an indoor growing tower, you can grow indoor lettuce year-round, creating an attractive indoor garden. Growing indoors reduces pest risks and can reduce disease risks with proper management.

Step 2 – Choose a Suitable Container

Select a container that is big enough to support the root system of the lettuce. A pot that is at least 6-8 inches deep is ideal. Shallow containers need to be watered more frequently, adding a maintenance burden.

Lettuce has shallow roots (6 – 12 inches/15 – 30 cm), so your pot should be at least six inches (15 cm) deep. Shallow roots also impact water management, but more on that later. Lettuce grows best if the soil is consistently moist.

If you only intend growing fresh greens, harvest immature plants and recycle new seedlings regularly, then the pot can be shallower, and you can grow lettuce closer to each other as it will never host mature lettuce plants. 

Several tower options allow you to grow lettuce at volume – as many as 20 plants per square foot. Most towers are modular, with each level allowing you to plant four lettuce plants. According to Prof. Bruce Bugbee, adding a blue grow light can help prevent indoor plants from becoming leggy.

Step 3 –  Use Suitable Potting Soil

Use soil rich in organic matter and offers good drainage. You can purchase a soil mix designed explicitly for lettuce or use a high-quality potting mix. Alternatively, you can make your potting soil.

Lettuce potting soil should be slightly acidic, so I recommend using coconut coir rather than peat moss; in this case, Sphargum peat moss will serve you better as it’s more acidic (pH 4.5).

The risk of using containers for growing plants, particularly indoor lettuce, is soil compaction (or insufficient soil oxygen). Adding an inert material like pumice or perlite will improve drainage and saturation porosity (the amount of air a soil can hold when water-saturated).

Finally, organic matter host beneficial microbes that plants need for their health and resilience. Mature compost is the most effective way of introducing a healthy population of microorganisms into your soil – even potting soil.

I find that vermiculite is too light for potting soil, and I use it only to cover my lettuce seeds, but more on that in the next step. 

Step 4 – Plant Lettuce Seedlings

You can purchase lettuce seedlings from garden centers, but they are generally sold in six trays, more than I need to keep an indoor garden going. I plant a few seeds weekly, ensuring I have a constant supply of young lettuce plants.

Plant seeds in an inert, sterile medium like pumice. In my opinion, the commercial seed starting mix is a gimmick, as all you need is a big bag of pumice or perlite (you can use it for starting all your seeds) and a small bag of vermiculite.

For seed starting, I plant lettuce seeds on the pumice and cover them with an eighth of an inch (3 mm) of vermiculite. That way, my lettuce seeds still get light (which they need to germinate), have limited germination resistance, and are insulated from temperature extremes.

Lettuce seeds germinate at temperatures as low as 45°F/7°C but prefer if the soil is around 60 to 70°F/15 -21°C. Watch out for using heating mats, as these generally run at about 77°F/25°C and won’t germinate if the soil temperature is above 85°F/29°C.

The seeds must be consistently moist after their first introduction to water. Any seed dehydration will kill the lettuce plants once seeds have emerged from dormancy.  

To prevent seed infections, throw the used soil away and replace it with fresh soil once you use a tray for germinating seeds. Lettuce seeds are sensitive creatures and risk being cross infected if the previous batch had latent pathogens.

If you’ve ever been told to use a spray bottle to cool your plants, please stop. Wet leaves are the fastest way to spreading pathogens. You can use a spray bottle to keep your seeds damp and prevent them from flooding, but that’s it for spray bottle usage.

Always purchase certified seeds with available expiration dates (lettuce seeds can only be kept for a year). After reading the above, you may prefer buying your seedlings from garden centers. I hope you break through the learning curve and grow your lettuce.

Seedlings take about a week to emerge after planting. Transplant the lettuce plant into your container, ensuring mature plants have adequate airflow around each plant. Loose-leaf varieties allow earlier harvesting. 

Step 5 – Keep the Lettuce Roots Hydrated

Keep the soil moist but not soggy. When about an inch of the top of the soil is dry to the touch, water ensures your container has adequate drainage holes. If you’re opting for glazed pots that offer better aesthetics, place a pot with enough drainage holes inside the glazed pot. 

Dark plastic containers tend to absorb heat and can get too hot. Heat and excess moisture are your most significant risks in growing different types of lettuce indoors.

Step 6 – Nutritional Requirements

Fertilize your lettuce every two weeks with a diluted liquid fertilizer. The essential nutrients for indoor lettuce are magnesium, potassium, phosphorus, and nitrogen. 

A balanced liquid fertilizer will ensure a good supply of the latter three, and the occasional addition of dissolved Epsom salts (1 tsp. per gallon) will supply the needed magnesium.

They should thrive if your lettuces have a steady supply of these essential nutrients, proper lighting, and a stable pH.

Step 7 –  Harvest Your Lettuce

Your lettuce is ready to harvest when you say so. Loose leaf lettuces are tasty as lettuce sprouts, but early harvesting reduces plant productivity. If you wait until the leaves are more significant, the taste won’t be compromised, and you’ll get more for your efforts.

Loose leaf lettuce is ready to harvest 25 days after planting, with the prospect of continually harvesting baby leaves for an additional 30 days. Cut the outer leaves near the base of the plant, leaving a few leaves for the plant to continue producing.

Nine Lettuce to Grow Indoors

There are quite a few options available for growing indoor lettuce gardens. As we saw earlier, planting lettuce is easy, and lettuce grows well indoors. Once you’ve grown your lettuce, you’ll realize nothing tastes like homegrown lettuce, and plants grown indoors seem to taste even better.

As far as fresh lettuce goes, there’s nothing fresher than a lettuce plant in your kitchen. While fresh lettuce from the garden is good, being able to pick an assortment of lettuce leaves from your windowsill.

1. Green or Red Oakleaf

Oakleaf lettuce has a loose, open head with long, lobed and fringed leaves. It tastes like most lettuce but with a milder flavor. The leaves are generally deep green and have a glossy, waxy appearance. Oakleaf lettuce is best used raw in salads and other dishes, as it does not hold up well to cooking.

2. Green or Red Romaine Lettuce

Green Romaine lettuce, also known as cos lettuce, has long, crisp stalks and dark green leaves. It’s a popular choice for salads, sandwiches, and wraps. Romaine lettuce is a good source of vitamin A, vitamin K, folate, and dietary fiber. It also contains small amounts of calcium, iron, and vitamin C. 

Red romaine lettuce is characterized by its long, dark green leaves with red veins and white ribs. It has a slightly sweet flavor and crunchy texture, making it a popular choice for salads and other dishes. It can be eaten fresh, fried, or as an ingredient in various recipes.

3. Red Sails

Red Sails Lettuce is a gourmet variety known for its bright green leaves with burgundy red frilly edges. Due to its sweet flavor and delicate texture, red sails lettuce is popular in salad mixes. This favorite is also easy to grow due to its natural resistance to bolting in the summer heat.

4. Allstar Mix

Because you want your salad mix to stand out from the crowd, this lettuce is a custom-tailored blend developed based on years of trial testing. Even in environments with less light, several types can produce reds and greens with deeper tones. 

Ruffled edges and unique leaf forms provide excellent performance, unusual texture, a long shelf life, and a good appearance. Included in this mix are the lettuces Lollo Rossa, Redleaf, Green Romaine, and Red Romaine, as well as Green Oakleaf and Red Oakleaf.

5. Black-Seeded Simpson

Simpson, Black Seeded Lettuce is a light-green, upright, loose-leaf type of lettuce. It has frilled rosettes and crumpled leaves, as opposed to tight-head lettuce variants and is regarded as one of the best-tasting lettuces with a light, sweet, yet substantial flavor. 

It should be noted, however, that this lettuce does not keep well. Because of its high water content, it spoils faster than other lettuce varieties. Keep this lettuce in an airtight plastic wrap or plastic bag after harvesting and use it within five days.

6. Buttercrunch

Buttercrunch Lettuce is a gourmet lettuce type distinguished by its silky, highly colored green leaves. This butterhead lettuce has a buttery, mildly sweet flavor and delightfully crisp, crunchy green leaves. 

Buttercrunch plants have soft heads with a rosette of open bunched leaves. Open-pollinated plants are simple to grow, heat-tolerant, and do not become bitter as growing temperatures rise. 

7. Ithaca

Fresh and light meals should be on the menu when the weather gets too hot. Ithaca head lettuce is ideal for making crisp, cold, refreshing salads or adding crunch to sandwiches and wraps. 

Ithaca is an excellent iceberg variety, producing strong, neatly wrapped heads with slow seed stalk formation. Heads keep crisp and tasty in the fridge, but we suspect your family will consume them as soon as they are harvested. 

8. Jericho

Jerico lettuce, also known as Green Ice lettuce, is a type of Romaine lettuce. Jerico lettuce is medium-sized with pale green leaves and is generally round or oval. Its leaves are tender and sweet, with a mild flavor that works well in salads. 

9. New Red Fire

New red fire lettuce is an heirloom loosehead variety developed in the 1980s. New red fire has red and green, slightly curly or crumpled leaves and a sweet taste. 

It is an excellent source of vitamins A, C, and K and is low in calories and fat. Red fire lettuce is excellent for salads, sandwiches, wraps, and more. It can also be cooked in stir-fries, soups, and other dishes. It is particularly heat and bolt resistant.

FAQs on Fresh Lettuce Indoors All Year Round

Summing it All Up

Mixing several lettuce varieties allows you to grow lettuce year-round to give a constant supply of fresh leaves. Lettuce is a source of dietary fiber, vitamins A and C, folate, and iron. Folate is essential for pregnant moms as it helps prevent certain birth defects.

The lettuce plant is easy to grow and allows you to harvest the outer leaves without compromising the plant. Some leaves have a buttery flavor, while head lettuces are more crispy.

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