Growing Lettuce Indoors

Growing lettuce indoors is easy but there are some tips you need to follow

We usually grow our greens and harvest in unheated season extenders outdoors until late December (yes, even here in the Canadian mountains zone 5!). In January we grow microgreens as it’s super easy, but as soon as we start our seeds to grow transplants we also grow indoor lettuce to harvest.

How do you grow lettuce indoors?

Do you need grow lights to grow lettuce indoors?

This is a common question, and this depends on your home, kitchen or window set up. As I mentioned we grow indoor lettuce when we start sowing our seeds and growing outdoor transplants. This is because we want to make the best use of our grow lights and not use them too much (you can see our indoor greenhouse and set up here).

All plants need light to grow. Lettuce is a cool season crop and can handle partial shade but they still need light.

This means you need to use grow lights or grow in front of a window for the best success.

You can also grow indoors with hydro or aeroponics. I haven’t had any experience yet with this growing method although I’d like to try in the future. There are many innovative ways to grow indoors these days!

Below you can see the Aerogarden in action.

Aero garden to grow lettuce indoors

What you need for growing lettuce indoors

Seed trays with drainage holes and without. If you’re using soil blocks or directly into the tray you’ll want that tray to have drainage holes and another without them so water doesn’t get all over your table. If you have pots you just need the trays with no holes.
Pots OR things like the potmaker (uses newspaper to make pots) OR a seed block maker (expensive to buy but again, this tool will last you years and has the benefit of not washing plastic pots covered with spiders every season/replacing the cracked ones).
Soil: Seed Starter Mix
Spray bottle and/or watering can. Make sure the soil is damp but don’t overwater. Read my in-depth seed starting 101
Optional: Grow lights (I use Sunblaster) and an indoor greenhouse or shelving unit to put a grow light on each layer.
Large table with a south facing window if no grow lights
Fan in the room or good airflow.

One of the biggest mistakes people make growing greens indoors is overcrowding

You have to thin out your seedlings to that other have the space to grow. The great thing is that you can harvest these seedlings, pinch off the root and you have some lettuce microgreens!

Another mistake is sowing too deeply, lettuce seedlings are small and barely need to be covered in soil

Once your lettuce is a couple of weeks old you’ll need to transplant them into larger pots. I usually use a 72 cell and sow seeds, harvest the microgreens, then transplant them into larger pots. You can learn how to re-pot your seedlings here.