Everything you need to know about growing lettuce indoors

As the growing season winds down and you near the end of being able to grow your favorite salad mixings outdoors, you may find yourself wondering, “Is there any way I can take this garden inside?”

The answer? Yes — at least for lettuce! Growing lettuce indoors is a fairly simple task, even for beginners, and it can be quite rewarding, too. Here’s how you can give it a try and ensure you’ll never have to run to the store for a salad base again.

Harvested lettuce in a bowl
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Why you’ll love growing lettuce indoors

Growing your own lettuce indoors has a lot of added benefits aside from bringing a bit of greenery into your space. Unlike store-bought lettuce, you’ll only have to harvest what you need for your meal that day and be able to leave the rest to live a bit longer. Homegrown lettuce is great for fresh salads, especially in the off season when you can’t grow a huge crop outside.

Believe it or not, it thrives inside

Because lettuce prefers a more stable environment, it has the potential to thrive indoors even more than it would outdoors, as long as you have the proper environment. You’ll be able to use up your lettuce at your own pace, replanting new seeds whenever you’re ready for a new batch. It’s important to note, though, that lettuce won’t grow forever. You will eventually have to harvest all of it, but it will last for longer than store-bought lettuce in a plastic bag.

Is it easy?

Lettuce is a fairly simple indoor crop to grow and care for, so growing lettuce indoors is as well. There are a couple ways you can do it — either hydroponically or from seeds in a pot. If you don’t have other indoor crops that you’re looking to grow hydroponically — or don’t want to spend the money until you’re sure about growing lettuce indoors — the easiest way to get started would be seeds in soil.

Start by finding containers that have good drainage and are big enough to hold a fully grown head of lettuce. This will vary depending on the variety you choose to grow, so be sure to take that into account. Good drainage is important for indoor growth (and any kind of container growth, really) because you don’t want the plant roots sitting in soggy soil. Since they aren’t planted directly into the ground, the space is limited. The excess water needs somewhere to go.

Slicing lettuce and a tomato
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Planting and caring for your lettuce seeds

Different seed packets may have varying recommendations for how many seeds to plant per pot, but a general rule of thumb is at least three seeds per pot. It’s always a good idea to do more than one because there’s no guarantee that every seed will be viable. Planting more than one per pot increases your chances of having sprouts.

The best growing conditions

Once you plant the seeds, ensuring the best growing conditions is essential to a great crop of lettuce. There are a couple things we recommend you keep in mind as you wait patiently for that first sprout to arrive.

  • Make sure the location you choose for your homegrown lettuce stays at least 60° F.
  • Keep your pots in a spot where they can receive between six and eight hours of light a day. This can be difficult to achieve, especially in the winter. But don’t worry! There are things you can get to help aid in the growth.

If all goes well, seeds should begin to sprout within a couple of weeks.

What to do with less-than-ideal conditions

If your indoor environment doesn’t meet some of the growth requirements of lettuce, you still have the ability to grow lettuce indoors! You just may need a little extra help.

If it’s lighting you’re lacking, there are a variety of grow lights — ranging in size and type of light — that you can purchase. You should look for ones that not only fit your space but are specific for lettuce/vegetable growth. Keep in mind that you may need different kinds of grow lights for different stages of the plant’s life.

If you’re looking to grow in a hydroponic system, you’ll likely need all of the above along with a proper hydroponic setup. There are ones that are pre-built, which can be ideal for those who are wanting to dabble in hydroponics but not commit to a full system (or those who don’t have the space for something elaborate).

Don’t forget the photoperiod

When we look at how much light lettuce needs, we have to consider its photoperiod. The photoperiod of any plant is also known as its day length, or the amount of time it’s exposed to daylight during a 24-hour period. The Department of Horticulture at Ohio State University (OSU) completed a study that estimated lettuce’s photoperiod was somewhere between 12 and 20 hours (which, for them, meant that the crop didn’t have a specific day length).

OSU concluded that a “shortened light cycle gave leaves a more compact and round shape, reducing self shading, allowing for a higher planting density but longer light cycle, one closer to the circadian rhythm of a plant, allowing for more slender and open leaves for better light interception.”

There are, however, variations between different types of lettuce. It’s always best to follow the directions for the specific variety you’re growing as most will indicate the photoperiod on the seed packets. A general rule of thumb is that, for best growth, lettuce will require at least eight hours of sunlight a day to ensure strong growth.

A freshly made salad
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Harvesting your indoor lettuce

Something to keep in mind is that even though homegrown lettuce will last longer than lettuce purchased at a store, it is still perishable. Lettuce plants will not live and produce new leaves forever; however, it is possible to keep a continuous harvest going throughout the year if that’s something you’re interested in.

When growing outdoors, gardeners will plant lettuce in batches about two weeks apart throughout the beginning of the season. This can be adapted to indoor growing using different pots/containers. You can start one set from seed in a container, then sow another set of seeds a couple weeks later. This will keep your harvest continuous throughout the year, and you can do this as much as you want so long as you have the containers and the growing space.

Once the leaves are about four inches long, they’ll be ready for harvest. You’ll want to start from the outer leaves and work your way in when harvesting, mimicking how you would break apart a head of lettuce purchased at the grocery store. This lets you use the biggest leaves first and gives the smaller leaves a chance to continue growing.

Growing lettuce indoors is one of the easiest places to start if you’re new to indoor vegetables. If you find you’re interested in branching out, there’s a whole world of indoor, basement, and small deck/patio gardening that awaits!

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