PLANTS THAT PRODUCE

Plants That Produce

Thinking Hydroponically

By Richard Frost

Hydroponics is a method for growing plants in a liquid solution, with or without the use of inert media for physical support of the plant and roots¹. The phrase “inert media” refers to aggregates that are not biologically active, including quartz pebbles, perlite, rock wool, and so on. A vendor who is selling a “hydroponics in soil” system is really just selling drip irrigation. There is nothing wrong with drip irrigation – but be aware that the fertilizers used in real hydroponics must be “urea nitrogen free”, whereas in a soil system it is desirable to have a portion of the nitrogen in urea form.

The first known use of hydroponics was the growing of off-season cucumbers for the Roman Emperor Tiberius during the 1st century AD¹. It then became a lost art in the western world but was restarted in Europe about 1700. Today, many melons, squash, and tomatoes sold in supermarkets are grown hydroponically. Think about it: when was the last time you saw a speck of dirt on a supermarket melon?

A rule of thumb in commercial agriculture is that compared to a conventional method, hydroponics is not economically viable unless your system is larger than 1,000 linear feet of troughs. So if you see a small outdoor hydroponics system for sale, just leave it. You are better off gardening outdoors in pots or in the ground.

Some people however must garden indoors and for that situation hydroponics is the most productive method available. Motivations for growing indoors include a total lack of outdoor space, inclement weather, or the less respectable enterprise of growing cannabis. Growing herbs, fruits, and vegetables indoors is not cheap. On a small scale it can be a fun hobby, with tasty treats as a reward several times a year. Shop around for fertilizer – there is no need to pay exorbitant prices for products with a trendy label. A good source of “how to” information here in San Diego is available from the folks at Innovative Growing Solutions, http://www.igshydro.com/.

Locally, we have large-scale hydroponics being used outdoors in flower production, ornamental plant propagation, and in food production. Most of the structures that contain them have partially transparent roofs so that lighting is not an issue. Of course we have a lot of conventional agriculture in these structures as well. Outside of our area, some farmers with a hydro-electric or geothermal power source on their property have found it more profitable to use their hen houses to grow crops hydroponically instead of raising chickens. Those of you with lots of solar power to spare could well consider becoming a closet tomato addict!

¹Hydroponics. Merle H. Jensen, University of Arizona. http://ag.arizona.edu/PLS/faculty/MERLE.html

SDHS member Richard Frost is a certified edible gardening nut. For copies of past articles and more information, please see www.PlantsThatProduce.com.

Reprinted with permission from March 2010 "Let's Talk Plants," the newsletter of the San Diego Horticultural Society, www.sdhortsoc.org