Aeroponics: Gardening without soil

Posted: Sunday, August 30, 2009

Some Juneau residents are enjoying the harvest of their outdoor gardens, but Andrew Hohenthaner is an indoor gardener who enjoys the science of aeroponics.

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Courtesy Of Hohenthaner Family
Courtesy Of Hohenthaner Family

Aeroponics is the process of growing plants in an air or mist environment without the use of soil. Hohenthaner gardens in a small 12-by-15-foot greenhouse in his back yard.

Hohenthaner's interest in aeroponics started during his high school biology and chemistry classes. He decided to get back into it last year and spent $1,000 to purchase his "top-of-the-line" aeroponic system, which is expandable and has room to grow 36 plants.

Hohenthaner's system looks like a science project, with tubes and pumps coming out of plastic trays. There are pumpkin flowers growing from succulent vines. The pumpkins didn't grow this year, but he did grow cilantro, oregano, basil, habanera peppers, lettuce, tomatoes, sugar peas and cucumbers.

Next year, he plans to grow strawberries and try the pumpkins again. This winter, he will move the entire system into his garage and keep growing.

There is no weeding to be done, no pesticides needed and no working in the rain.

Hohenthaner, 48, finds it peaceful to be in his greenhouse tending his plants with his growing lights providing the light. This one of the disadvantages to aeroponics in Juneau; he has to use grow lights.

His first plants grew in 38 days and he is now growing a second crop of plants. Hohenthaner said that his basil plants are producing three pounds of basil per week. He grabs some basil leaves rubs them together and breathes in the aromatic smell of the fresh basil.

Plants can grow faster in an aeroponic system, because they are continuously being fed nutrients. The roots grow in a closed plastic container and water mist is sprayed on the roots to create 100 percent humidity. Air is circulating in the system which prevents the roots from rotting.

Aeroponics is different from hydroponics. The roots are growing in air instead of water. The seedlings are started in a spongy material called rockwool, which looks like a loofah sponge. The roots of the plants grow through the rockwool and hang down in the air.

Hohenthaner adds a mixture of inorganic salts to the water and monitors the water quality. Adjustments to the chemical balance of the water can result in different tastes and the plants growing different.

"I would like to point out to people these are the same (nutrients) that are in soil. We are just taking that nutrient and mixing it in water," Hohenthaner said. "The water in Juneau is incredible. It's under 38 parts per million of suspended solutes. I don't have to tweak the water at all."

Hohenthaner's water supply, which continuously recycled in the aeroponic system, comes from a garden hose. He believes aeroponics could be done commercially in Juneau.

"We could supplant some of the fruits and vegetable coming from down south to minimize the food miles."

"This is a sustainable three season capable gardening program. If you had a building you could do it all year," Hohenthaner said. "Consider the food miles involved with the distance our food travels before we eat it. Consider the economic effect and the environmental effect. Even if it's organic, we've burned so much fossil fuel to get it here, it's a moot point."

However, not everyone is a fan of aeroponics. Local gardener Joe Orsi said the system is expensive to install and has to be monitored closely. Orsi gardens very successfully in the soil and admits he doesn't have much knowledge or interest in growing things with aeroponics.

These things may be true, but Hohenthaner is undeterred by the expense of his system or the technical knowledge that is needed to grow plants successfully. He is content with his hobby size green house for now but dreams of a bigger commercial operation that could provide a year round supply of fresh, locally grown produce to Juneau grocery stores.

• Erik Stimpfle is a writer living in Juneau. He can be contacted at stimpfle@gci.net.



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