Can you be green and have a green lawn?

June 20, 2011

In my neighborhood in the early 1980s, we spent the summer playing kickball and bocce and an epic hide-and-seek competition we called “manhunt.” Our front lawns were a constant. We took their soft, grassy goodness for granted, until the lawn service arrived. Now and then, a tanker truck pulled up, and two men in coveralls sprayed who knows what all over our grass. Before they left, they put up little flags reminding us to keep off the lawn for 24 hours. For emphasis — or the pre-literate — the signs featured a skull and crossbones.

In part because of those tanker trucks, grass has taken a major public relations hit. Its constant need for fertilizer and herbicides is supposed to make it an environmental disaster. Such luminaries as Michael Pollan tell us that lawns are unnatural and reflect an embarrasing, peculiarly American need to conquer the natural world.

Well, I’m not embarrassed. I think grass is awesome. Call me an unreconstructed suburbanite, but I think children should be able to frolic on front lawns. A bed of forsythia and lilacs is a dreadful playing surface for kickball.

Unfortunately, if you get it wrong in our area, the negative environmental effects of poor grass management can be significant.

Grass is now the biggest crop in the Chesaeake Bay area, and will soon surpass all crops combined. Excess chemicals placed on lawns at the wrong time or carelessly scattered on impermeable surfaces can end up in the fragile bay. Excess fertilizer, to take just one example, contributes to eutrophication, a process that occurs when too many phosphates and nitrates build up in a body of water, feeding an explosion of algae. When the algae decompose in the bay, they use up much of the available oxygen, choking off crabs and other marine life.

So is it possible to be environmentally sensitive and have a good lawn? Yes, according to Frank Rossi, an associate professor of horticulture at Cornell University, who offers a crib sheet: “When people at a cocktail party ask me how to have a great lawn, I tell them to prepare the soil, choose the right grass, mow it high and fertilize it no more than twice a year.”

It’s that simple, he says. No mysterious chemical brews required. Now here’s the longer version.

“The number one issue is choosing the right varietal,”
says Mark Carroll, an associate professor of turfgrass management at the University
of Maryland. “The right grass for a golf course isn’t the right grass for a home lawn.”

Carroll and his colleagues subject new varieties of grass to an extensive, five-year testing process to see how they fare in the variable climate of Maryland, Washington and Virginia. They publish a list of the certified grasses, which you might have better luck finding at a nursery than at a big-box store.

Now that you’ve got the right grass, you have to prep your soil. If you can’t easily insert a screwdriver into the ground, consider tilling. And, while you’re at it, work a modest amount of composted plant matter into the dirt. But don’t go crazy with this step.

“You can have a decent lawn on poor soil,” says Rossi. “The stuff grows through cracks in the sidewalk, so it can’t be that picky.”

Once your grass gets going, here comes the really hard part if you’re trying to maintain a healthy lawn without chemical intervention:

Leave it alone.

You read that right. According to both Carroll and Rossi, the biggest mistake people make is failing to control their impulse to intervene. They mow too short and too often. They water too much. They fertilize too frequently. And, when things go bad, they break out massive amounts of chemicals to try to control the advancing weeds.

You should mow your grass to a height of three inches. And don’t mow it again for 10 days. Two weeks if you can stand it. Why? Because plants naturally maintain a ratio between the length of their roots and the length of their shoots (the visible grass, in this case). When the grass gets too short, the plant doesn’t send roots deep into the ground in search of water and nutrients. That allows weeds to snap up the resources — which sends people running for herbicides and pesticides.

As for fertilizer, do it twice a year, at most. But don’t even think about doing it in the early spring.

“Grass has a natural growth spurt in the springtime,” says Rossi. “It doesn’t need fertilizer at that point.” So don’t fertilize until the spurt ends in late May or early June, then fertilize again around Labor Day. If your grass looks okay, skip the fertilizer altogether.

Be tidy about it when you use it. “Any fertilizer that lands on an impermeable surface” — such as a sidewalk or a driveway — “will find its way into the Chesapeake Bay,” says Carroll.

It’s also best to avoid fertilizers that contain phosphorous. It doesn’t dissolve in water as well as nitrogen, so it’s more likely to be carried into the bay by runoff. Phosphorous is also a bigger contributor to algal blooms, which is why the legislatures in both Maryland and Virginia this year passed laws restricting its use.

As for watering, do it only once or twice a week. If mushrooms develop, you’re watering way too much — and wasting water. It’s better to give your lawn a good weekly soaking than to water a little every day. If there’s always moisture available near the surface, the roots won’t go down in search of water.

If you can keep your meddling hands off the lawn, you probably won’t need chemical pesticides, herbicides or fungicides. The good news is that today’s chemicals are much less harmful to the environment than the ones used 30 or so years ago.

“The 1970s pesticides were broad-spectrum chemicals with toxic effects across different organism classes,” says Carroll, referring to both humans and our animal friends. “Today’s products affect only plants. The active ingredient has also been reduced by a factor of 10, a hundred, or even a thousand in some cases.” So it’s probably okay to spot-treat, but keep it to a minimum. We still don’t fully understand the impact that the sprays have on amphibians, birds and insects.

One last tip: Don’t be one of those suburbanites. “This is a lot easier if you don’t try to make your lawn look like the center field at Nationals Stadium,” cautions Rossi. “You don’t need perfectly uniform grass all the time.”

In other words, if you can roll a kickball on it, you can be content.

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