Home & Garden

IT'S WAR ON WEEDS

Weeds are amazing. More often than not, they're beautiful. A vacant lot with chest-high barley rippling in the wind is a glorious thing, especially when it's jumping with sparrows feasting on the seeds. Add to beauty weeds' benefit. They do so much cooling, aerating and stabilizing of vacant lots and roadsides that Harvard horticulturist Peter Del Tredici has taken to celebrating weeds as "spontaneous urban vegetation."

But when a mother lode of seed from these fast-breeding, water-hungry plants germinates in a garden, particularly a drought-tolerant garden in Southern California, it's war. It's a water war.

By weeding after winter rains, you can allocate water to the right plants and cut off the thirsty interlopers. You'll snare the seeds of weeds before they can spread. You'll also clear out a sweaty little under-zone of greedy greens that block air and light from the plants that you want to thrive.

The benefits are clear. The question is how best to achieve them. You are never more of a gardener than when you weed. You are physician, botanist, architect and explorer.

Though it sounds incongruous and wasteful, experienced gardeners often water a couple of times in advance of winter rains in order to force weeds up. Pull this crop, and you reduce the spring surge. The process is essential for wildflower gardens if the poppies are to survive early competition from crab grass.

As effective as this strategy may be at reducing the early winter weed load, seeds still blow around and are tracked by cats, birds, dogs and us. Weeds don't germinate on cue, either. Part of what makes them so formidably successful are complex triggers calling for successive rounds of sprouting. Dandelions are the first to react to lengthening days. Rye grass responds to water.

Weeds can be grasses, vines, shrubs or tree seedlings. The one thing weeds have in common is that they all love disrupted soil. Del Tredici says they especially love disrupted soil that is irrigated and fertilized.

In other words, weeds love our gardens.

The best way to control the explosion of weeds in a good rain year is to get them while the soil is moist and the temperature is mild. A battery of tools and techniques bespeak a gamut of philosophies about how to do this. Mow them down. Rake them out. Yank. Dig up each one with a fork. Poison them.

Which to use? The answer lies in situation, size and ethics.

For weeds in lawns, most homeowners just mow, though every spring certain companies spend a lot of money exhorting Americans to treat yards with "weed and feed" products targeting dandelions, clover or anything else that might attract a bee. The herbicide in this mix is usually 2,4-D, or dichlorophenoxyacetic acid, which works by overwhelming the weed's hormone system. In dandelions, it essentially causes the plant to grow itself to death.

Arizona State University environmental chemist Thomas M. Cahill once explained this process as "cancer for plants." Among critics of the approach, discussion continues as to whether it causes cancer in people.

For crab grass under fruit trees or in hedges, rakes and hoes are the answer. Rake back the mulch, then use a hard-tonged rake or hoe to take out the weeds. Once that's done, smooth over disturbed soil and restore the mulch. Even water it lightly to stop the soil from drying out.

UC Davis weed guru Joseph DiTomaso is a fan of the hula hoe, also known as the stirrup hoe. It can clear a weed-clogged fence border fast. Under fruit trees, I use a hard-tonged bow rake. It pulls plants with minimal soil disturbance.

In flower beds, particularly wildflower beds, pulling weeds by hand is best. Do this immediately after a rain and in the early morning or late afternoon, when the soil is moist and any disruption of the crust can be quickly and neatly patted down to protect roots of neighboring seedlings. When pulling, grasp as close to the root crown as you can get, then feel for the angle of least resistance and tug. The less soil you unearth while weeding, the more skillful you are becoming.

If the roots run deep, or if you're dealing with dandelions' tap roots, then a garden fork is helpful. Better yet, DiTomaso says, are long slender tools such as the asparagus fork (also called a weeding knife) now in fashionable garden tool supply catalogs. Slip the fork down the root line, wiggle slightly and tug.

Not sold? Anything long, strong, sharp and slender should do the job. If rye grass rises between pavers, try an old screwdriver, slowly moving it along the soil and flipping out the weeds.

Bermuda grass, particularly its deep-running rhizomatic roots, can seem indestructible. That's what the turf guys who bred it for sports fields intended. Gardeners who need to clear large expanses of it often resort to the herbicide glyphosate, sold under the brand name Roundup. But for the average lot, especially one with plants that you don't want to kill, removing Bermuda grass by hand is the safest route. A pick or lady shovel will be the best tools — both if you want to alternate which muscles you use.

If taking out existing lawn, then you'll need to turn over the entire space. At roughly six-inch intervals, chop the soil to roughly 4 inches deep, feel for roots and remove them, shaking off excess soil. Once you've separated the roots by hand, go over the soil with a hard-pronged garden rake to smooth it out and to catch broken strands.

Be thorough, but become forensic only in places where you are preparing for new shrubs, bushes or trees. If any new shoots appear in these places, get them out immediately before the sapling becomes established. You do not want Bermuda grass root insinuating itself around or below the trunk of the sapling; the Bermuda will choke its competition.

When dealing with recurrences or spot incursions of Bermuda grass, don't start chopping. Follow the tendrils with your fingertips, tugging as you go. New shoots should come up easily. When the tendrils snap, you've found an established root zone. At this point, stop and pierce the ground deeply and find the missed root. Disrupt as little soil as you can. Remember: For a weed, disruption is opportunity.

It may take years to beat Bermuda grass, but it can be done. DiTomaso advises regular pulling of surface growth so you cut off energy being fed to those hard-to-get roots, eventually starving them. Skip the compost bin, and give Bermuda grass roots to city recyclers, who can cook them to death in professionally tended heaps.

Some weeds, such as burclover, are noxious. Burclover's little yellow flowers are pretty but produce stinging burs that bedevil many a dog paw. The plant is so easy to pull, one must admire its ability to weaponize itself.

Weeds such as rye grass and clover can be highly beneficial. They sequester nitrogen, offer forage for honeybees and bring the Irish luck. Others are escapees from the nursery and turf trade: passion vines, morning glories, pittosporum trees, sunflowers, Mexican fan palms, Chinese flame trees and the dreamily fragrant coyote bush.

As you weed, you may not want to pull some. Contrary to the truism, weeds are not plants in the wrong places. Plants that grow in spite of us are generally in the right place — for the plant.

In his newly released book, "Wild Urban Plants of the Northeast," Del Tredici points to the benefits that modern cities derive from their default vegetation. He poses an intriguing proposition for gardeners and landscape designers: What can we learn from weeds? If they are so well equipped to live here, how can we incorporate them into the way we design and tend our cities?

The answer may be far off, but this much is clear: The people who come up with it will have done so on their hands and knees.

Green's column on sustainable gardening appears weekly on our L.A. at Home blog, latimes.com/home. Comments: home@latimes.com.

Copyright © 2014, Los Angeles Times
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