Restoring Soil

Several people commented on last week’s column on the carbon cycle. All endorsed the concept of restoring garden soil, to support its natural ability to sequester carbon.

One reader had questions about how to go about restoring garden soil. This is a Big Topic and you, good reader, might have your own questions, but you also might share his interests. My brief responses are below. Visit gardening.com for more details, including plant suggestions.

Q. Plow the grass under?

A. Losing the thirsty lawn is a good first step, because such monocultures are not appealing to wildlife. Plowing, however, could both promote re-growth of the grass and bring dormant weed seeds to the surface. A better approach is to kill the grass over several sunny weeks by covering it with clear plastic (solarization), or with newspaper or cardboard (smothering).

For information on Soil Solarization for Gardens & Landscapes, visit the University of California’s Integrated Pest Management webpage on the topic. The presentation emphasizes pest control; in this context, unwanted turf grass amounts to a pest.

The California Native Plant Society has Detailed lawn removal advice.

Q. Plant different grass?

A. Yes! California native grasses can provide the basis of an attractive meadow, which is more casual than a manicured carpet of turf grass. A meadow has unique aesthetic appeal; supports a variety of wildflowers and wildlife; requires little water, infrequent mowing, and no chemicals; and helps to restore the soil.

Kids on Native Grass Lawn
JACQUELINE RAMSEYER —
BAY AREA NEWS GROUP

Lily Baker’s front yard in San Jose
features a native grass lawn.
California native grasses help restore the soil.

For information on several California native grasses, visit the Tree of Life Nursery’s web page, “Masses of Grasses.”

A very good book by Carol Bornstein, David Fross, and Bart O’Brien is Reimagining the California Lawn: Water-conserving Plants, Practices, and Designs (2011).

Q. Grow more trees?

A. Absolutely! Trees and large shrubs are attractive additions to the landscape, valuable participants in the carbon cycle, and welcomed by all forms of wildlife. Invest a little research to select trees will thrive in your climate, and grow to an appropriate size for your landscape. Again, California natives are good choices.

A good introduction to California native trees and larger shrubs is available from the non-profit Nipomo Native Garden, which has produced a web page, “Native Trees for Landscaping and Wildlife.”

Q. Eliminate ground cover in favor of something with deeper roots?

A. Ground covers are any plants that hug surface or rise to any height up to four feet. Most importantly, they protect soil and soil microbiota from baking in the sun, or eroding. During the fall and winter, plant seasonal cover crops that draw nitrogen from the air and store it in their roots. Examples of such “nitrogen-fixing” plants include peas, beans, and clover. In the spring, before your cover crop sets seed, till the plants under to decompose and release their nitrogen into the soil to support the growth of other plants.

Deeper roots mean better drought-tolerance: deep-rooted plant can find moisture far below the surface. Such plants are generally preferable in the landscape, all other factors being equal.

The depth of roots varies among plants, reflecting adaptation to the plant’s environment. Among weedy grasses, for example, Annual Bluegrass (Poa annua) has roots only about right inches deep, while Bermudagrass (Cynodon dactylon) can grow to 60 inches deep in search of water.

Infrequent, deep irrigation encourages all plants to develop deep roots and drought tolerance. A common error with automatic irrigation systems is to schedule frequent, brief periods of watering. This practice encourages shallow roots, ultimately increases overall water usage and leaves plants vulnerable to dry periods.

Q. Shallower roots?

A. The advantage of shallower roots is that plants growing in arid climates have immediate access to occasional rains. Succulent plants have adapted to such conditions by developing shallow roots and the ability to store scarce moisture in their leaves, stems or roots. For this reason, gardeners often appreciate succulent plants for both drought tolerance and landscape appeal.

The New California Garden, which we envision here, features meadow grasses and succulent plants: a good time to start is now.

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