Know How: Go Soil-Free or Create Your Own Soil in Gardens

No Soil? No Dirt? No Problem!

Gardening in San Diego can be a challenge: While the climate is ideal for a wide range of plants, high property values and poor soil conditions put traditional gardens out of reach for many residents. Containers and raised beds are both time-honored solutions, but technology and soil science also make it possible to go soil-free or even to create your own soil.

Going Soil-Free with Hydroponics

In hydroponic systems, plants are not rooted in soil but held in gravel, bark or other mediums and fed a liquid nutrient solution. Hydroponic gardening includes aquaponic, vermiponic and aeroponic variations. Supporters say these plants are nearly free of soil-borne diseases and that the closed systems use a fraction of the water required by conventional gardens or farms.

Aquaponics combines raising fish with growing vegetables. Fish waste provides the nutrients to grow vegetables while the plants purify the water for the fish. The lucky gardener gets salad and a main course from one efficient system!
Vermiponics uses worms to boost the nutritional content of the system and is still very experimental, although worms play a vital role in helping breakdown compostable products.

Aeroponic systems leave plant roots exposed to the air. One space-saving aeroponic system, the Tower Garden, positions plants vertically around a central tower and a small pump delivers nutrient solution directly to the roots. San Diego resident Lori Wooldridge uses the home version of the Tower Garden and also distributes them. She finds her Tower Garden to be so productive that good timing is necessary to avoid being overwhelmed by the harvest.

Soil-Creating Gardens

If electric pumps and nutrient solutions don't satisfy your gardening urge, why not put the principles of soil science to work for you?

The basic idea behind these soil-creating gardens is to build a compost pile, cover it with a layer of finished compost or good soil and plant your garden on top. Plants initially take root on the surface, and as the season progresses the compost materials break down and become rich soil to feed further growth.

In an age of disappearing topsoil, proponents of this method delight in growing their own garden soil and assert that this can even be done on top of contaminated soil or pavement. Here are three variations on this theme:

• A lasagna garden bed derives its name from the layers gardeners create as they pile compostable materials like straw, cardboard, leaves, coffee grounds, tea bags or grass clippings together to create a raised bed. After layering, the bed is covered with several inches of soil or finished compost, and planted.
  
• In straw bale garden beds gardeners saturate straw bales with a high-nitrogen nutrient solution. As the initial heat of decomposition subsides, gardeners add a few inches of soil or finished compost and then plant.
  
• Composting keyhole garden beds can be built the same way as lasagna garden beds, but are circular and constructed around a central composting core.

All three approaches are inherently do-it-yourself options, but local groups such as Sustainable Solutions can provide guidance and lead workshops on these gardening techniques in the San Diego area. After one such workshop, Jeff Bishop, with Sustainable Solutions, said, "It's so amazing that we can take this garbage—cardboard, food scraps, old leaves, coffee grounds—and, with a little knowledge and a little work, convert it into soil for growing vegetables. We have the ability to fix many, many problems with this approach to gardening."

Whether you choose to grow your own soil or to forgo the use of soil entirely, there are many ways to conquer the challenges of limited space and limited soil to create a city garden. What's your garden solution?