Is Crabgrass in your lawn?


I admire tenacity. It is a trait that I strive for myself and have tried to instill in my child. I am moved when I hear stories about people who overcome adversity or achieve great things by trying repeatedly until they reach their goals. And yet, when a great example of tenacity occurs right in my own backyard, I find myself strangely unmoved.

The model of tenacity is crabgrass (Digitaria), and now is its high season. For those who have just moved in from some barren planet, crabgrass is an annual weed that appears in mid to late summer. It emerges from the ground to form spreading mats of growth. It takes over if given even half a chance, and is very difficult to irradicate. The Latin name for the genus, Digitaria, is very appropriate. “Digitus” is the Latin word for finger, and crabgrass is distinguished by the long finger-like projections that it sends out in all directions. Long ago someone looked at a crabgrass plant with its “fingers” fully spread and decided that it looked like a green crab, hence the common name.

As with many irksome things, the government was responsible for crabgrass. In 1849 it was introduced into the United States for use as a forage plant. Crabgrass settled in faster than you can say “herbicide” and has lived here in not-so-peaceful coexistence with homeowners ever since.

I have crabgrass around the edges of my lawn and here and there in my flower beds. There would be more of it in the lawn if it were not for the clover that seems to out-compete it. On balance I don’t mind the clover, so I concentrate my efforts on removing the crabgrass from amidst the flowers. Beds, where the spaces between plants have been covered with layers of newspaper topped with mulch, are well defended against crabgrass and other weeds. In sufficient quantities mulch by itself also deters the weed’s spread. When crabgrass does rear its ugly head, I usually hand weed, being careful not to wait so long that the crabgrass sets seed.

Crabgrass is so tenacious that it has spread itself all over the Internet as well. My eye is drawn to the website of a well-known herbicide producer. After going over the undesirable traits of crabgrass, the text reads, “crabgrass can overtake large sections of your yard throughout a season or two, especially if you have an older, tired lawn that hasn’t been renovated for many years.” Since this describes my lawn to a “T”, I take note.

Generally I try to steer clear of herbicides because of what they might do to the more desirable plants, not to mention the local birds, beneficial insects, my cats and any other sentient entity in the area. Fortunately, the University of Minnesota Extension Service has help for people like me. They claim that a healthy dense lawn, properly tended and fertilized, is the best protection against crabgrass and other problem weeds. They also suggest keeping the grass at about 3-inches long. This is a little taller than some people are used to, but it shades the ground enough so that sun-loving weeds stand less of chance of sprouting. As a final alternative, the Extension Service recommends waiting until spring and applying one of the pre-emergent weed killers in areas where crabgrass plants tend to congregated

So I continue my hand weeding. It is a tranquilizing pastime, and it is a legitimate excuse to avoid cleaning my house, straightening up my desk or taking on other stultifying domestic chores. As the crabgrass piles up in the weed basket, I consider the fact that it is not without redeeming qualities.

For one thing, crabgrass does indeed make great cattle forage. Research has shown that cattle fatten up quickly on a crabgrass diet. As if that weren’t enough, cattle prefer the taste of crabgrass to almost everything else except Johnsongrass (another common weed). The researchers also discovered what home gardeners have known all along—that crabgrass grows in thin soil and cares little about adequate drainage. It is also a nitrogen lover, and responds to nitrogen supplied by legumes. This would explain why crabgrass and clover, a legume, stand proudly, shoulder to shoulder at the edge of my lawn.

You may welcome crabgrass to your north forty if you are troubled by toxic petroleum waste. In Arkansas, scientists are studying ways of rehabilitating soil around oil wellheads that has been contaminated for years by heavy oil. Sometimes the contaminated soil is a foot thick with a black crusty layer covering a deeper layer of tar-like goo. Crabgrass seed germinated in this mess at a rate of 78%. Of the seeds that germinated, 64.5% survived. Those survivors not only lived but thrived spectacularly, making it ideal for “phytormediation”–slow and steady rehabilitation of extremely contaminated soil.

So while you and I and every other gardener continues the good fight against the crabgrass that outcompetes both the lawn and the ornamentals, we can celebrate the fact that someday crabgrass could help save the world. But keep pulling. Rest assured that the inroads we make on our lots will do little to hinder its ultimate triumph.

Yellow Rose

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