Gardening Articles: Edibles :: Herbs

No-Soil Gardening

by Howard M. Resh

What started years ago in laboratories is today a system of crop production used around the world. It is also a way for home gardeners to produce high-quality fresh vegetables, herbs, and ornamental plants efficiently year-round.

Even though commercial and homemade systems are simple and reliable, hydroponic gardening retains its laboratory aura. Hydroponics began when scientists isolated and studied the six requirements for plant growth: temperature, light, water, oxygen, carbon dioxide, and mineral nutrients. Their goal was to determine the optimum amounts of each of these factors for a specific plant--an impossibility in soil outdoors.

The surprise came when the scientists got all the growth requirements just right. Gardeners who witnessed the astounding growth under these conditions were early converts to hydroponic gardening. Other advantages include no heavy soil to dig, no weeds to pull, and no soil pests and diseases to overcome.

Now in winter, with fresh vegetable prices rising and quality falling, is a good time to start growing your own crops indoors.

Types of Hydroponic Gardens

While the basic principles of all hydroponic gardens are the same, three basic systems have proven practical for home gardeners. In each case, plants grow in a sterile medium, instead of soil, and a small pump cycles a nutrient solution over roots.

Nutrient film technique (NFT) gardens are easy to build at home and are well suited to a variety of vegetables and herbs. They work by constantly passing a thin stream of nutrient solution past roots. Plants grow in specially designed channels such as gutters or PVC pipes.

Ebb-and-flow gardens are best for growing anything potted, such as house plants. A watertight tank or tub periodically fills, then drains back into the nutrient reservoir.

Drip gardens deliver a nutrient solution to plant roots using the same types of emitters as in outdoor drip-irrigation systems. Draining nutrient solution can be trapped and recycled, or allowed to drain away.

Growing Media

Instead of soil for root growth, hydroponically grown plants need a porous but stable and inert material. Different materials can work, depending on the situation. Washed, 20-grit sand, various gravels, redwood bark, polyurethane foam, coconut fiber, perlite, and vermiculite will serve. But the two you're most likely to encounter and use are rock wool and some type of expanded clay.

Rock wool is manufactured by melting rock and extruding it into fine threads that are then pressed into loosely woven sheets. These sheets are cut into cubes, blocks, and slabs. Chief advantages are its ability to hold water and still provide excellent air circulation around roots. It is also very easy to work with. Compared to other materials, it costs somewhat more.

Expanded clay is manufactured by heating various kinds of clays in kilns. The clays expand rather like popcorn. All provide excellent air circulation and don't break down quickly. They are most often used for potted plants in an ebb-and-flow system and are available under various brand names.

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