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Growing Hydroponic Lettuce

It all started back when I was in the fourth grade and I designed a rocket ship to take me to Mars. My teacher, Mr. Clark, had a strong science background and got me thinking about some of the nuts and bolts of space travel: what would I eat? How would I have enough oxygen? So, with his help, I designed a hydroponic system: my plants would grow in water, producing oxygen and food for me, and using the excess carbon dioxide we, the space travelers, produced. We'd be traveling in a self-sufficient space capsule - sort of like earth itself.

That was about 50 years ago, but I've had a hankering to grow some hydroponic food ever since. So, when I met Marcy Stanton at a New Hampshire Master Gardener conference and learned she grew hydroponic vegetables in her home all winter, I made arrangements to go see her system. It was late January and she had plenty of fresh basil growing under fluorescent lights, ready to add to salad or soup.

Stanton gave me the basics to start up: a styrofoam bin with a lid and some little plastic pots with slots that allow roots to grow through, called net pots. She explained that I also needed some potting mix and fluorescent lights that I could adjust to keep the lamps about six inches above plants. No problem, I had that stuff.

Stanton purchases a special hydroponics solution for her growing medium, but it contains chemical fertilizers, and I'm an organic guy, so I used Neptune's Harvest Fish and Seaweed Fertilizer instead, and it has worked just fine. I used two tablespoons per gallon of water as my solution. I wondered if the smell of the fertilizer might be noticeable in the house, but it's not - except when I pour some in.

If you search on-line you will find all kinds of products for hydroponic growing, many of which cost hundreds of dollars: special lights, pumps, containers. My favorite was Dr. Hornsby's Iguana Juice sold as hydroponic fertilizer (contains krill and yucca extract, earthworm castings, guano, alfalfa - but no iguana products). Great name, but at $29.95 per liter, I didn't buy any. It's available, along with net pots, at www.hydroempire.com or 888-434-9376. Another supplier that had net pots is found at www.hydroharrys.com or 800-461-8819.

The styrofoam bin Stanton gave me is the kind used to ship frozen steaks or fish, perhaps. It is 17 x 11 inches, and the base is about 5 inches deep. The cover sits up another inch and a half. This bin has room for six pots, and in each pot I am growing two plants. Because the reservoir base holds about two gallons of solution, watering, especially when the plants are young, can be done once every couple of weeks. I also bought a food-grade plastic food storage container that is 12" x 10" and 4" deep, and it works fine though contains less liquid and will only handle 5 net pots. I used a box cutter to cut out circles in the lid.

To get started I filled the net pots with commercial starting mix, which is mainly peat moss and perlite. This is coarse enough that it won't wash out through the holes in the net pots, which is important. I tried using vermiculite, but it all washed out when I put the net pot in the solution.

Stanton advised me to wait until the plants had established roots before placing them in the hydroponic system. I just kept the growing medium slightly moist, and waited for them to develop a set of true leaves, then eased the pots into the reservoir.

Apparently algae can be a problem if the water solution gets too much light, so Stanton advised me to line the Styrofoam container with a large plastic bag to help keep out light. The lid, of course, allows some light through, but still I have not had algae growing in the solution - or at least not yet.

Unfortunately, I don't think I can transfer the lettuce into the soil outdoors once the ground warms up. The roots are already 8 inches long, and pass through the slots of the net pots, so they would break off if I tried to remove the plants from the pots.

Truth be told, growing hydroponic lettuce is fun, but the quantity I can grow in two containers is not significant. I have used the lettuce in sandwiches, but a couple of dinner salads would pretty much eat up my supply. Next winter I think I will plant basil and other herbs, things that I can't easily get at the grocery store and that will really spice up a salad. And what about my trip to Mars? It'll soon be outdoor gardening season. I think I'll stay put.

Henry Homeyer is the VT/NH associate editor of People, Places and Plants magazine. His website is www.gardening-guy.com. He may be contacted at gardening.guy@valley.net, or P.O. Box 364, Cornish Flat, NH 03746.