Crabgrass

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october, at home, Pittsburgh

The school routine is well established now, and the temperatures outdoors no longer remind us of summer's end but of winter beginning. For months, we have watched tall, rangy masses of green rising at the back edge of our lawn, and now these awkward stalks are blooming butter-yellow feathery goldenrod, clean white fuzzy boneset, deep early morning pink tufts of joe-pye weed, and my favorite, bright purple ironweed. If I have managed to save any yarrow from the mower, it flowers now—though I enjoy its feathery leaves, flowers or none.

The suspense begins in watching the crabgrass (Digitaria san-guinalis) die back with the first frost. Have my efforts at seeding perennial grass succeeded? Is the clover still alive under there? If crabgrass looked green all year, we'd cultivate it, but when it dies, I get a chance to see the price I pay for my lack of lawn service. I regard it a small price—a couple of pounds of organic lawn seed every fall, sprinkled among the dying crabgrass, will soon sprout pretty and green for the winter. I used to imagine that if I kept seeding, the crabgrass would give up. This fall I nearly resigned myself that this annual seeding may be a regular ritual, but I can hope for the best and still continue the practice. Rachel Carson, it seems, believed that this should work:

There is a cheaper and better way to remove crabgrass than to attempt year after year to kill it with chemicals. This is to give it competition of a kind it cannot survive, the competition of other grass. . . . By providing a fertile soil and giving the desired grasses a good start, it is possible to create an environment in which crab-grass cannot grow, for it requires open space in which it can start from seed year after year. (from Silent Spring)

This is the effort I have been making, and perhaps with a bit of added soil and another round of seed, I'll finally get that competitive lawn she describes.

Almost every time I am asked what my graduate work was in — the topic still arises periodically—the homeowner is both amazed and interested, at least briefly, in the fact that I studied weeds. I can almost see them thinking, "Now that's a topic I can start a conversation about." Dandelions come up as a topic most often, and crabgrass runs a close second for most conversation-inspiring weed. With dandelions, I have a difficult time sympathizing—I've seen some ugly vacant lots infested with them, but the tamer lawn version doesn't inspire any real venom from me. Yet with crabgrass, I began to understand as soon as I first met our backyard. Crabgrass in summer means three other seasons of mud.

My first fall here, I learned that in the process of dying, the crabgrass has a few days of looking beautiful, at least in color—sometimes yellow, sometimes a bit purple. In summer annual flowers, these colors are typically signs of nutrient stress. Crop nutrient deficiencies can be diagnosed by leaf discoloration patterns. Similar to the way in which dandelion flowers are unattractive for some people because they are a sign of the impending appearance of their scruffy seedheads, crabgrass senescence in fall is unappealing primarily because it means a bare, muddy spot in progress.

I have two theories, at least, about why one patch of our backyard is particularly thick with crabgrass. The dog leash left in place by the previous homeowners would explain the region of crabgrass through foot traffic, compaction, and nitrogen burn. Crabgrass does fairly well in compacted soil and also tolerates, even thrives, on high levels of added nitrogen from ammonia. My less accusatory theory is simply that this section of lawn — the top of a slope — is drier and more compacted because it is close to the house and shed. Either way, if I simply aerated it and applied some compost, it would better support our desired lawn grasses. Both of these options are laborintensive, and when I have that kind of energy, I tend to find other chores to use it on.

In either case, new lawn grass seed has, so far, been my only weapon against it. When we bid on the house, it was early March, and after the negotiations were complete, just before leaving town to begin packing our apartment in Chicago, my in-laws and I bought a few pounds of grass seed and applied it liberally over what appeared at the time to be a solid swath of mud. By early summer, when we moved in, the yard was much greener, and I had a temporary sense of victory. That fall, as the crabgrass turned rosy and yellow, I seeded again and optimistically watched the seeds sprout as the weather cooled. Through the fall, my seeding again sprouted green grass, and I felt happy about my efforts, perhaps even smug.

Through that first winter, I realized I had a perfect weed science research plot. By the next summer it was clear to me that regular seeding was helpful but not a fast solution, so I set up the experiment. As the second year's crabgrass began to die, I marked off plots and seeded again. This time, though, some plots got grass seed alone, some got clover plus grass, and some got nothing. In spring, other plots got the same seed treatments. For a while, I optimistically watched the various plots, some with thick clover seeming to choke out the crabgrass. Mentally, I was writing up the scientific paper as I watched.

Months later, I looked out the window from our study and saw the crabgrass turning yellow again, seemingly uniform and unhindered. I decided that however wonderful the experiment had looked earlier, it was now a bust. Seeding new grass over dying crabgrass does help, and it is a cheap, easy solution to winter mud, which I could repeat every year for the rest of our years in this home. If I'm looking for a solution that results in dramatic improvements, I'm going to have to do what I'd been avoiding: aerating and adding organic matter. This would mean using some good compost, and not simply fertilizing, but trying to improve the soil. I don't know if I should do it as an experiment or simply across the whole patch of crabgrass, on faith that these steps can't do any harm, and might help. I'm still trying to decide how much I really mind a bit of crabgrass in the backyard. Some part of me wants to beat it, to prove my expertise at weed management; another part of me is afraid to really try, lest the crabgrass show itself my superior in combat.

Around front, we have no crabgrass, but we have other problems. I get the sense the front lawn, as usual, was taken a bit more seriously by the previous homeowners. The problem there is not crabgrass but thatch. Thatch is a brown patch of dead lawn grass, so thick with dead leaves that even the crabgrass seems unable to penetrate. When we moved in, thatch was abundant in our front yard. I remembered my parents using a metal rake on the grass in autumn, and so our first autumn I raked viciously and seeded after. I found that some dead spots were simply a mat of grass roots and stems sitting on top of the soil. The sense I still get is that at some point in our lawn's past, the front yard was laid out with fresh sod, but that the sod never connected to the soil beneath. I can reach into the dead grass with my fingers, and pull, and whole sections come up, as if they were simply laid down on top of the bare earth. In the bare patches below—clean soil punctuated with a few white grubs—I seeded with new grass and clover, which grew nicely. However, the soil was uneven, since I'd pulled up a good inch of soil with the grass roots, and then when we mowed we ended up with a very amateur-looking haircut. In removing thatch again this year, I added topsoil to the fresh bare patches before seeding, and I think I'm finally learning. I now have to search a bit to figure out where I worked, which is a vast improvement over being able to see my lawn patchwork from the street.

One cause of thatch is poorly applied fertilizer. Surface-applied fertilizers encourage growth of shallow grass roots and denser leaf growth, but during times of drought (the normal condition of August in much of the United States), these thick, shallow-rooted grasses can't survive. Our lawn grasses in the Northeast are primarily cool-

season grasses. Though they can go dormant in August, if they grew beyond their root systems in June, they're more likely to die rather than just hang on and wait. When they die, the mat of dead vegetation prevents water from reaching the deeper roots. Grass plants in that area die, and new plants can't germinate through the thick, dead grass. If you dig, you'll find grubs, but that doesn't prove grubs to be the cause of the problem — they may simply be opportunists. As I discovered our first year, it isn't enough to rake off the dead leaves, because the dead root mat won't support healthy new grass seedlings.

I know that many lawn owners seem to do fine using commercial fertilizer, but I have to say, I suspect that pesticides, fertilizer, and lawn watering are all on the same team. Once a lawn is fertilized, it needs water to help the fertilizer reach the roots. Weed seeds, lying on the ground surface where they blew in on the wind, are happy to try to scavenge the fertilizer and water before it soaks into the grass roots. Corn farmers address this problem by putting nitrogen fertilizer into the soil with a tractor-drawn tool called a knife, so that the fertilizer goes to the corn roots, not the surface weeds. Also, if pesticides are used, the lawn becomes a single-species expanse, all plants needing the same nutrients at the same time. So, if you start with pesticides, fertilizer is going to be needed next, to address all those hungry, uniform grass plants. Once you fertilize, you'll need to water again, and the cycle continues. Lawns typically need all, or none, of these artificial inputs, and a middle-of-the-road approach creates neither health nor beauty. Fertilizer, without adequate water, will lead to thatch, and then the only good news is that crabgrass doesn't germinate on thatch either.

One radically different solution to crabgrass and bare patches, which I found more or less accidentally, is to create a garden over the crabgrass patch. This idea began opportunistically, when I was looking for a sunny spot for our tomatoes and snap peas. So, where to put the garden? It seemed a shame to tear up good grass when we had so many marginal areas. Also, the healthy lawn grass—not coincidentally, as crabgrass thrives in full sun—was mostly in areas of partial shade. The dog's leftover crabgrass patch seemed perfect, with full sun exposure on a gentle slope. By putting the garden patch on the slope, I could cut down on some of the more difficult mowing as well. I knew I couldn't simply dig up the crabgrass and plant vegetables, so after digging a three-by-three-foot square and edging it with thin concrete blocks, I filled the garden with a few bags of purchased topsoil plus a few shovelfuls of our own compost. My ideal would have been to use only our own compost, but we didn't have enough yet, even for such a tiny garden. I suspect we can never have enough compost.

When we were city dwellers, we grew a jungle of flowers and herbs on our back porch, but our failures with potted tomatoes were so monotonously predictable that my greatest craving for our suburban yard was real tomatoes. As any number of writer-gardener-activists — lately Alice Waters and Barbara Kingsolver, especially— have pointed out, kids are more likely to eat vegetables if they participate in cultivating or harvesting. Our oldest daughter introduced her summer babysitter and friends to mulberry trees in Chicago, because they could pick them outside and climb trees, and mulberry is a fruit that I'm sure I couldn't convince anyone to eat based on its looks. But she has consistently been willing to try foods if my husband picks something outdoors and says, "You can eat this, see?" He takes a bite, and she says, "I want some!" All of our many failures in the arena of introducing new foods seem to apply only indoors. Perhaps prehistoric children who lived in caves learned what's edible by foraging with a beloved, trustworthy grandmother. But now that we have space for a garden, I'd be a fool not to take advantage of this loophole in our daughter's narrow palate.

For this new garden, I wasn't sure what to expect in the weeds department. Tolerant as I am of weeds in lawns, I do recognize that their benefits in gardens are limited. I'll let an occasional lamb's-quarters live for salad, but I certainly didn't want crabgrass all over my vegetable garden—I've said how much I really dislike handpulling grasses. I needn't have worried, as even with just three or four inches of added topsoil, the crabgrass didn't trouble the garden at all. That year, I discovered that two tomato plants are not nearly enough for us, and even with snap peas thriving around the entire perimeter, our daughters could eat the entire harvest daily and still want more.

Our nine square feet of garden was really only a test run, I knew, and I envisioned a room-sized backyard vegetable garden eventually. I'd read about the benefits of small squares of garden, and the idea was particularly appealing for me after spending that summer with my own third-acre and a hoe. Starting small would guarantee I could keep up with weeding. With a small garden, I can reach the center without standing in it, which means cleaner shoes and looser soil. This summer, I added two more squares, also located in the sunny section of crabgrass. I didn't expand into the area I'd marked for my crabgrass overseeding experiment, but I plan to keep on expanding to new squares for a few years yet. I figure the worst that can happen is that I'll get overwhelmed with produce, and the next year I can seed the garden with grass and revert to mowing, or seed the garden with native grasses and have a mini-prairie. Either way, the garden will derail the crabgrass cycle.

Even in a front yard, where vegetables are a sign of rebellion against societal norms, gardens can help us break up the crabgrass. Any crabgrass-infested patch is sunny enough for flowers, and few yards would look the worse for an additional flower bed. Let the garden designers skewer me for heresy (though they'll probably have to stand in line behind my weed science teachers), but I'm declaring that crabgrass is telling me something I need to know. Just as the violets in spring say, "Shade here!" the crabgrass in fall says, "Lousy soil here!" If I'm not willing to watch it grow, I can at least listen to it, on my way to get myself a load of garden topsoil for a new plot of next summer's vegetables. That way, even if I'm looking at mud all winter, it will be the tidy rich garden soil I installed with my own hands.

Winter

Winter may, according to the calendar, begin on December 22, but I think of it as beginning just before Thanksgiving and ending around March 1. During this time, we spend more time indoors than in any other season. We travel for the holidays to see my parents and my husband's parents in Kentucky and my husband's grandparents in Missouri, giving us at least one car trip across the farm belt, with its fields covered in snow or chickweed for the winter. Our observations of many weeds in this season are through windows, and I discuss two here: Japanese knotweed through car windows and on hillsides throughout Pittsburgh, and poison ivy vines through our upstairs bedroom windows, still clinging where they died.

None of us can stand to be indoors the whole season, though. When it snows, we go out and sled, ski, and build snowmen. On milder days, we go for short hikes, playing with ice of all sorts. I take walks out in the yard for a moment and imagine what the yard will be like the next year. Some weeds are flat and leafy in the garden now, the broad, soft grayish leaves of mullein, or the deep green, spiny leaves of thistle. These weeds look harmless, but they're also at their most vulnerable. It is in winter that I have at least three months to consider at leisure the question of whether or not to let them go to flower next summer.

Sometime between late January and early February, we begin getting the occasional warm spell, with a sudden melting of any insulating snow and a liquefying of any muddy patches from last year's crabgrass. In these thaws, I always gratefully notice clover, green and sturdy, holding its own beauty through the winter.

And so, in winter, I see both the standing dead remnants of last year and the dormant, green plants that might bear next year's flowers. I see which plants are protecting the soil with leaves, and which ones have left only stalks. Our daughters, now five and eight, celebrate the occasional snow day with joy, and I try to get in the spirit of it with them, between meetings, January's new semester of classes, and other obligations. Despite the cold, many of the best moments of winter are still the ones when I find myself outside.

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Responses

  • patrick
    Is crabgrass a medicinal weed?
    2 years ago

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