Growing Lettuce Indoors in Winter

A great indoor project for gardening in winter is growing lettuce. Yes, you can grow and enjoy homegrown lettuce even when it is below freezing outside. In fact, some gardeners keep lettuce growing year round! Other gardeners enjoy just a bit of a break from the gardening season, but most gardeners I know are once again eager to be growing something by mid-winter.

If you’d like to grow your own lettuce inside, here is what you will need:
– potting soil
– a small container, such as the plastic containers much produce now comes in at the grocery store (anywhere from 5 inches by 8 inches or larger)
– lettuce seeds (see tips below)
– a warm spot to germinate the seeds
– a fluorescent light fixture with two 40-watt cool bulbs hung over a shelf
– a tray for placing underneath your container
– a timer for the light fixture

Seed Tips
For indoor-grown lettuce, do not choose an iceberg variety. Instead, choose a butterhead, bibb, small romaine, or looseleaf type. ‘Buttercrunch,’ ‘Winter Density,’ and ‘Matina’ are all excellent choices. Any of the varieties marketed for micro-greens or baby heads are also good ones to try. The seed catalogs for 2010 have already been hitting our mailboxes for about a month now, so if you don’t have any lettuce seeds that you want to use yet, you can easily order from your favorite catalog. Additionally, many local garden centers stock lettuce seeds at this time of year precisely for we gardeners who like to grow it over winter inside.

What To Do
1) Moisten your potting soil. If you (like me) still have some potting soil from earlier this year, it is still perfectly good to use. You’ll probably notice it is bone dry though. Pour some into a bowl or bucket and add some water. You’ll need to leave it for at least an hour or two to absorb the water. Add more water until the soil is damp throughout.

2) Cut holes in the bottom of your container. Using a pocket knife or another sharp knife (resist the urge to use your good kitchen knives if you can), cut drainage holes in the bottom of the container. For a 5-by-8 inch container, at least six holes are needed.

3) Put a good 2-to-2.5 inch layer of the potting soil into your container.

4) Carefully sprinkle up to 20 lettuce seeds over the surface of the potting soil.

5) Cover the seeds with 1/4 inch of potting soil.

6) Spritz with water. If you’ve gotten the potting soil pretty damp, you can skip this step.

7) Put the lid back on your container, and you have a nifty little micro-greenhouse.

8) Place the container somewhere warm (though not so warm that it will dry out the soil quickly) for the seeds to germinate. The top of your refrigerator is a perfect spot.

9) After a week, start checking the container daily to see if any seedlings have sprouted.

10) Once several seedlings have sprouted, thin as needed. (You want your plants about 2-to-3 inches apart.)

11) Move your container onto a tray under the fluorescent lights and set the timer to keep the lights on 12 hours a day.

12) Keep the soil evenly moist. You may need to water once a day. Give the plants some half-strength balanced fertilizer once a week.

13) After a few more weeks, your plants should be large enough to start harvesting the side leaves. At this point, if you’d like you can pot these little guys up into a larger container (like a plastic windowbox) and start another round in your original container.

That’s all there is to it! Enjoy your winter lettuce.

Photo and text contributed by Carey Harrington, Certified Colorado Gardener