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The Dry Garden: Best ways to kill your lawn

December 3, 2010 |  9:00 am

Lawn
Most of us know that the environmental toll of ornamental lawn in Southern California makes cigarettes look politically correct. Still, removing a long-tended home lawn takes a meeting of conviction and know-how. The steely inspiration will have to be yours. This column is intended only as a lawn killer's tip sheet.

There are three dominant schools of turf removal. One advocates removing the grass, another suggests poisoning it and a third calls for smothering or cooking it. Which one you choose will depend on your convictions about pesticide use, the amount of time you have and what's in the target lawn.

For many of the older homes, lawn is not one type of turf but a mix of plants, often dominated by warm season grasses such as Bermuda and St. Augustine, then studded with persistent weeds such as nutsedge and bindweed.

Warm season grasses get their name because they are dormant in the winter. What makes them such foes when it comes to removal is a formidable underground network of roots. Fragments of stems called stolons or rhizomes can quickly produce new lawn come spring and summer.

This regenerative power is why Nan Sterman, a lecturer on lawn substitutes at the Water Conservation Garden at Cuyamaca College and an L.A. at Home contributor, warned: Whatever you do, don't rototill the soil, because that will chop up and spread those roots. "It will multiply your problems exponentially, Sterman said.

This is one reason why Gene Ratcliffe, instructor of a popular lawn-removal course at Tree of Life Nursery in San Juan Capistrano, opens her classes by holding up a shovel and a blade sharpener and admonishing, "You'll be needing these." Those with dense lawn thatch and clay soil might prefer a pick with blunt end for chopping and a needle nose for cracking tight knots of roots.

Whether you chop out the lawn yourself or hire a crew to do it, there is much to be said for digging out warm season grass in the winter, not least the cool working conditions along with the moist and therefore pliable nature of the soil. Although winter is planting season in Southern California, be careful about a hasty succession from lawn to new garden. Where Bermuda grass has been freshly cleared out, do not plant right away unless the soil has been thoroughly filtered by conscientious hands, or even passed through a sieve.

When the weather warms, even the most conscientious gardener will soon see evidence of remnant stolons. The key then, warned Ratcliffe, is to get right in and remove the stragglers before Bermuda grass tendrils insinuate themselves into the roots of newly planted shrubs and trees. From this point onward, weeding work will be restricted to shallow, careful digging around the new plants. The object will be to deny any photosynthesis of new grass shoots feeding nutrients to those lingering stolons.

Because some lawn types can be so persistent, Rancho Santa Ana Botanic Garden horticulturist Bart O'Brien is not shy about recommending the herbicide glyphosate. "Bermuda grass, bindweed and nutsedge are where I draw the line," he said. "If you have these bad weeds, then I do say use Roundup."

If this sounds like a fast approach, it isn't. Using a spray bottle so he could work around established plants in his home garden, O'Brien applied the glyphosate during warm months, watered the plants to see what survived the pesticide, then applied it again. It took him two years of treating and watering the yard of his nearly 100-year-old Upland home to completely clear it of persistent lawn grasses and weeds. Only then did he begin planting a successor garden of native plants.

For O'Brien, the reward has been relatively easy weeding of grasses that sprang from migrating seed rather than deeply rooted remnant stolons.

If you're lucky enough to have a lawn dominated by cool season grasses such as annual rye or red fescue, then O'Brien and others see no reason to use pesticides. Removal is relatively easy. To get both the seed and the plant, Missy Borel, program manager at the California Center for Urban Horticulture at UC Davis, recommends sheet mulching.

The process involves mowing the lawn down to the ground, then covering most of it with cardboard or newspaper, topped off by three inches of compost. (The area right next to the curb will need to be dug out by hand.) Do not irrigate it, Borel said.

This carpet will smother the grass and prevent seeds from germinating, while breaking down over time to provide a rich new layer of soil. Those wishing to start a vegetable garden can punch through the sheet to start right away, she said. However, the method should not be used within the drip line of established shrubs or trees, where you don't want lawn anyway.

Sterman calls this method "cover and smother," a variant of which is solarization, which involves covering the grass with plastic sheeting in the summer. The plastic traps heat that cooks the grass and seed. If you need this method, you're probably battling Bermuda grass -- in which case Sterman is skeptical that the process will affect the deepest set roots. Tree of Life co-founder Mike Evans is further skeptical about solarization, citing effects on beneficial soil micro-organisms.

To the mind of Los Angeles garden designer Ben Oswald, eradication of any lawn grass, particularly in a single pass, amounts to wishful thinking. After removing St. Augustine to make way for his native garden, he concluded: "Nothing’s absolute. You have to see what works and be patient." After a pause, he added, "Weeding is really fun."

-- Emily Green

Green's column on low-water gardening appears here on Fridays.

Photo credit: Kirk McKoy / Los Angeles Times

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