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 lettuce indoors to harvest.

Tips for growing indoor lettuce

Growing Lettuce Indoors Supplies

  • 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.
  • 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.

Growing Lettuce Indoors Under Lights

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 in our mini greenhouse and not use them too much.

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

Indoor growing set up for growing lettuce or seedlings indoors

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 indoor garden ideas these days!

Aero garden to grow lettuce indoors #indoorgardening #aerogarden
Aero garden to grow lettuce indoors

Growing Lettuce Indoors in Containers

One of the biggest mistakes people make growing greens indoors is overcrowding in their containers.

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!

Common Mistakes In Growing Lettuce Indoors - Overcrowding

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 containers. I usually use a 72 cell and sow seeds, harvest the microgreens, then transplant the seedlings into larger containers.

After about 4-5 weeks you can harvest baby greens! Sow frequently and you have spread out fresh harvests.

Fresh Greens: Harvest Baby Greens & Salad Leaves Year-RoundWould you like to learn more about growing greens year-round?

Check out my ebook on growing greens year-round!

Fresh Greens book- Grow Greens & Salad Leaves Year-Round



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