How To Grow Lettuce Indoors - Easy!

I have begun a successful indoor garden. Three cheers for me! Hip, hip, HOORAY!

Indoor gardening can get messy and complicated, depending on what you’re trying to grow. What I am growing is the one crop that I can’t get to taste yummy if I grow it outside: lettuce. I am also growing it without any soil.

Why can’t I grow lettuce outside? Two words: sandy soil.

First of all, lettuce likes to drink water all day long. So if the soil isn’t constantly moist, the plant begins to taste bitter way before it’s ready to bolt.

Water seeps through sandy soil like a sieve. As a matter of fact, even when I watered every day, the lettuce tasted bitter before it was even halfway to maturity!

Second of all, the roots of lettuce grow shallow. Unlike other crops, they can’t reach deep down and try to find water that has seeped down. Not that there’d be any water deep down on our property, where in many places you hit bedrock after digging only two to three feet down.

I should mention, as well, that I live in the Southern U.S., where – unless we get a mild winter, which we can’t be guaranteed – we only have a short time in the spring, and an even shorter time in the fall during which the temperature is perfect for growing lettuce.

Fortunately for me, lettuce happens to one of the few kinds of plants that is easy-peasy to grow hydroponically, especially for indoor gardening. Lettuce doesn’t mind if some algae grows on its roots, and it doesn’t care if the pH of the water or the amount of nutrients isn’t perfect.

Let me tell you, was I excited the first time I harvested lettuce from my indoor garden – and it tasted sweet!

My indoor garden-the top two shelves are covered to protect our eyes from the bright LED grow lights.

Materials for growing lettuce indoors

• Metal shelf (ours came from Wal-Mart).
• Growing lights (more on that in a moment).
• Three to four boxes that are about three inches short the length of the shelf. I’m using shallow Sterilite® storage boxes. You could also build boxes out of wood and line the inside with builder’s plastic or 6-mil black plastic (6-mil white is too delicate).
• Dry hydroponic fertilizer (look around on Amazon; I currently use General Hydroponics® MaxiGro, but it’s not vegan so next time I’m going to purchase a vegan fertilizer).
• A package of large (at least eight-ounce) plastic cups, at least one cup per head of lettuce you plan to grow (possibly two – see my “optional” comment in a moment)(I squeeze a dozen cups into each box – trust me; it is a squeeze once they start to get big!).
• A bag of pea gravel.
• A growing medium – I prefer “coco peet”, or “coir”. You can use a soilless planting mix if you want, or even sand. The best indoor gardening set up is a low-mess set up. ;)
• Lettuce seeds (duh – but I have to put this on the list or one day somebody might try to sue me because they tried to grow lettuce indoors without any seeds, and it’s my fault nothing grew because I didn’t put “lettuce seeds” in my materials list. Welcome to America).
• Optional – two-inch net cups. I had already purchased a package of them, so that’s what I use for growing the lettuce. If you don’t have them and don’t want to buy them, use half of the plastic cups you bought for containing the water, or buy smaller plastic cups for this purpose.

A word on grow lights

You have a few options in the world of grow lights for your indoor garden. I recommend one of two, for affordability and efficiency.

The first is the old-fashioned fluorescent light fixtures, with two bulbs that each produce light on one of the spectrum ends. Go to your local hardware or big box home improvement store and ask an associate for a “shop light fixture.” It will probably be longer than your shelf. If you don’t like that, you can try to find something online that fits the length of your shelf exactly.

My 2 fluorescent light fixtures on one shelf. Yes, you need two per shelf if you go this route.

The shop light fixtures - side view.

Then you want to get two bulbs. One should be on the “cool” end of the spectrum, the other on the “warm” end (it will tell you on the label). The bulbs don’t use a whole lot of electricity as long as you’re not turning them off and on (which you won’t be), and you’ll get nice growth. This set-up is also more likely to locally available to you, while the next may not be.

However, I recommend this next one over the basic shop light option for two reasons. First, the lights will allow the lettuce to produce all the phytonutrients in an indoor garden that they would if they were growing in the sun. Fluorescent light bulbs do not. Second, they use even less energy than the fluorescent. They are also a lot easier to handle than shop fixtures with those long bulbs.

I’m talking about red and blue LED growing lights, easily available from Amazon. They’re inexpensive and lightweight. The one big disadvantage of these lights is that they are so bright, looking at them is like looking at the sun. I have the two shelves utilizing LED grow lights covered on three sides (the fourth is against the wall). I can do that because it’s in the bathroom, so it’s not like we have to look at it all day.

Unplugged LED grow light fixture. Looks weird b/c I'm pointing camera up at it from bottom of the shelf.

As far as I’ve been able to tell, you get equal growth from either light set-up. So if you don’t want that bright of a light emanating from your indoor garden, just use fluorescent lights – but understand that you won’t be getting all the nutrition from them you would get with the red and blue lights.

Growing the lettuce

1. Moisten the growing medium. Or, moisten a paper towel if you want to start the seeds in a plastic bag that way. Sometimes I get better germination doing that.
2. If you’re not using paper towels, fill your smaller cups or net cups with the moistened medium.
3. Sprinkle three or four seeds into the medium, and press into it gently. If you’re using a paper towel, sprinkle seeds on one half, and fold the other half over and seal it inside a plastic bag.
4. Place the cups on a saucer or in some shallow container that will hold an inch of water or so.
5. Pour water onto the saucer whenever most of the water has been sucked up into the cups.
6. If using a plastic bag, tear the piece of towel off with a germinated seed and sow it into the growing medium in a cup as soon as you notice a teeny green sprout. Seeds will germinate within a week or two, depending on the variety (I've found that red varieties take longer, for some reason).
7. KEEP THE SEEDLINGS NO MORE THAN TWO INCHES AWAY FROM THE LIGHT until you move them into the larger cups. Use small cardboard boxes, stacks of magazines, pieces of scrap wood, etc. to hold the saucer with the seedlings close to the light. Keeping tabs on where the seedling is in relation to the light is probably the most complicated part of indoor gardening.
8. In the meantime, fill up the larger cup (without holes) with pea gravel to the level where, when you place the smaller cup inside, the edge of the smaller cup is right about the same height as the larger cup. (Using net cups will require more gravel.)
9. Fill up a gallon jug or other container with water, and add the recommended amount of hydroponic fertilizer (this is called nutrient solution).
10. When the lettuce has at least four leaves, move the smaller cup from the saucer to inside the cup with the pea gravel. 

    

    Sorry about photo quality. This shows a net cup, lifted up from the pea gravel inside the plastic cup. Notice the lettuce roots growing out the sides of the net cup.

11. Fill the larger cup with the nutrient solution, until maybe 1/4 to 1/2 inch from the rim.
12. Place the cup in one of the boxes.
13. Keep the lights turned on at least eight hours per day.
14. Refill the cups when the nutrient solution gets below the pea gravel, to where you can’t see it from the view from above the cup.
15. You can “cut and come again” when the plant is at 1/3-1/2 maturity, or you can wait until it’s completely mature and harvest it all at once.
16. Rinse the pea gravel and cups out whenever you discard and old plant, to get the algae out.

By the way, I have a cilantro that is growing well using this method, and I know others who have grown basil in this simple, non-circulating hydroponic way, as well.

Indoor gardening is fun! Yes, the initial set-up is expensive, and it will take you awhile to recoup your investment compared to the cost of purchasing lettuce (or herbs) from the store. But this method, once set up, is easy and low-maintenance. And the produce you harvest will be much fresher and more nutritious than what you can even get from a high-end health food store or good farmer’s market.

Now that you know how to grow lettuce indoors, have fun starting your indoor garden!