Salad garden on a deck rail … it's hydroponic

Sunset, April, 1988

Salad garden on a deck rail . . . it's hydroponic

The word "hydroponics" came into U.S. dictionaries 50 years ago. Mostly, this practice of "growing plants with their roots in nutrient mineral solutions rather than in soil" takes place under lights and uses other artificialities that put it outside Sunset's interest. Here, however, we report a hydroponic garden where plants grow in natural light and the planter is attractive to the eye.

A cornucopia of vegetables and berries grows in a planter that spans the railing of Anne Wright's back deck in Laguna Beach, California. Tomatoes, romaine and red lettuce, onions, strawberries, cucumbers, and bell peppers all rise from a 9-inch-deep, 18-inch-wide, 14-foot-long box. To gardeners accustomed to dirt gardening, it's hard to believe this densely packed assortment flourishes in so shallow a space and without soil.

The planter is filled with crushed pea gravel (1/4 to 1/2 inch). To feed the plants, a mixture of water and water-soluble nutrients circulates through the planter four times a day, for an hour at a time. It can easily seep through the loosely packed gravel around the plants' roots.

When the water isn't circulating, it drains into a plastic garbage can set below the planter. The idea is to feed the plants frequently, but also allow time for air to circulate in the gravel so roots won't rot.

The upper part: the planter

Designed and built by John H. Rudolph of Laguna Beach, the system uses off-the-shelf components from a lumberyard, a garden supply, and a hardware store.

The planter's sides and bottom are 2-by-10s. To speed drainage, the bottom slopes gently (1 inch in 10 feet) from one end to the other. The side facing the deck bolts to railing uprights; the outboard side rests on 4-by-4 posts set in concrete. (To give added support, you could run 2-by-4s from the railing to the posts.)

Folding a piece of 6-mil polyethylene into an open-topped "box" shape and stapling it inside the 2-by-10s gave the planter a watertight lining.

Gravel does not completely fill the planter: 10 inches from the low end, a barrier of hardware screening (nailed to the sides and to a 1-by-2 crosspiece) blocks the gravel but lets the water through to a drain.

The garbage can is filled with surprises

A 32-gallon plastic garbage can serves as reservoir for 20 gallons of water and nutrients. At the bottom of the can, a small submersible pump connects to a line of plastic tubing that leads to the far end of the planter. Nearby, an electric outlet with a timer runs the pump.

A water line to a toilet float valve fills the can to a predetermined level when needed. Most of the time, the line is shut off so water won't flow in when the pump is running. (But even when the pump runs, there's enough water in the can to keep the pump submerged.)

The garbage can sits below the planter's low end; water returns directly to the can through two drain lines built into the planter. As the sketch shows, the shorter one is flush with the planter's bottom; the other rises about 6 inches above the bottom. In the shorter line, made of 1/2-inch PVC, a watertight seal is accomplished by running a male-threaded slip connector through a predrilled hole in the planter bottom and into a female fitting. Silicone caulk seals the hole. The taller line uses 1 1/2-inch PVC fittings. Both enter the garbage can through holes cut in the lid.

The 1 1/2-inch drain line can carry overflow, should the smaller one get clogged; but its main purpose is to act as a sleeve for a stick that shows how much water is in the can. The stick, a piece of pine molding, is mounted to a toilet float. When the can contains the right amount of water, the top of the stick rises slightly above the drain line. When the stick doesn't show, it's time to add water.

A hose bibb on the can allows drainage.

Growing a hydroponic garden . . . she starts with seedlings in sixpacks

Although some hydroponic gardeners grow their plants from seed, Ms. Wright found that seeds tended to wash away, so she starts with seedlings in sixpacks, rinsing all the soil off the roots. She spaces plants just far enough apart to allow for the mature size of the vegetables. If a plant gets too big or starts to crowd a neighbor, she gently dislodges it from the gravel and moves it. Plants in a hydroponic system tend to get off to a faster start than those planted in soil and to mature a week or so earlier.

The strawberries Ms. Wright tried were eventually pulled out, since they did not produce very well. But the vegetables have consistently yielded bumper crops.

The fertilizer used here is specially formulated for hydroponic systems. It contains all the major and minor mineral elements for plant growth, at the proper level of acidity. It's rarely sold at nurseries, so you may have to order by mail or from a hydroponic supplier; check in the yellow pages under Hydroponics--Equipment & Supplies. A 1-pound package (about $10) will feed a 20-gallon hydroponic system for about four months.