Prostrate Spurge

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august, at home, Pittsburgh; and june 1995, THE western KENTUCKY wEEDs TOUR

Accompanying the hawkweed in my friends' suburban Greenville lawn grew an entirely different sort of weed, flat and green. Prostrate spurge is hawkweed's opposite: a plant that grows close to the ground, with a flower so dull and inconspicuous that even with a magnifying glass it could be of interest only to a botanist. It actually doesn't even really require mowing. Prostrate spurge is a summer annual, which means its primary drawback in the lawn is its disappearance during the cold season. If you don't look closely, it looks dark green and pretty all summer, and when seeds set and frost sets in you've got a brown patch.

Spurge grows in the strangest places, sometimes seemingly without soil. Anything that grows in the compacted, poor soil of a brand-new lawn deserves a bit of respect for its tenacity. But prostrate spurge (Euphorbia maculate) is the weed you'll find first between the cracks in your sidewalk, where you didn't realize there was enough soil to support a single root. I actually admire it in one place in my yard, which is the high-salt, rock-dense soil just to the right of our driveway, which I mentioned earlier in speaking of our poor driving aim. Prostrate spurge is the plant that grows in this demilitarized zone, between our not-so-proper lawn and bare soil.

I've seen it most commonly on farm roads; they aren't used so often that they become muddy, but they're compacted enough that little else will grow.

Spurge is one of the few weeds whose name makes it really sound like a weed. It rhymes with "scourge" and sounds like "discourage," and if you were to cast aspersions on spurges, you wouldn't be the first. I can hardly imagine either a crop or ornamental with such an unattractive name as spurge, though my children might argue that asparagus is comparable.

Prostrate spurge belongs in a family with a whole range of reputations. Poinsettia (Euphorbia pulcherrima) is the most strikingly beautiful member, the plant that is grown in Mexican greenhouses in summer, is left in dark places for a few weeks, and comes out with these amazing, colorful faux-flowers just in time for the holidays. I say faux-flowers not only because I've recently seen poinsettias in suspicious shades of dyed blue and green at our grocery store, but also because the colors are on leaves, not flowers. The real flowers are actually just little nondescript white-and-yellow nubs at the tips of the stems.

The bad-boy member of the family is leafy spurge (Euphorbia esula), an invasive weed of cattle rangeland that is so unpalatable that cattle won't even graze near it. Leafy spurge, then, shrinks the effective acreage available for feeding. The most useful member of the family is petty spurge (Euphorbia peplus), which is interesting for its oddly personified name, but useful because its milky sap can be used as an out-of-the-ground treatment for skin cancer lesions. The sap is applied to the lesion like liquid nitrogen, and like liquid nitrogen it causes skin blistering and cell death where it is applied. The cancer generally flakes off a week or so later. The milky sap is common to most members of the Euphorbia family. Break a leaf off your poinsettia and watch the sap run. Cactus-like members of the family can be distinguished from real cacti, whose family is conveniently called the Cactaceae. Euphorbia cacti are like cows: they have two horns and give milk. (Translation: The spines come in pairs, rather than clusters, and if you pull off the bud next to the spine, the plant oozes white milky sap.) But don't feed this milk to your kids or your pets because it is quite toxic. The technical term for it is "latex," and if you have latex allergies, your body is unusually well primed to protest contact with the natural plant version of the stuff. In that case, definitely don't eat your poinsettia.

Prostrate spurge was one of the first weeds I was asked to identify during my master's program, or at least I think it was, because I was able to figure it out only later. My initiation into the world of weed science was a roughly four-day-long weeds tour, an annual road trip from central Kentucky, with its rolling hills, pastures, and woodlands, to Western Kentucky, which has a lot of flat cropland like the Corn Belt. Western Kentucky, the region's moniker, is always capitalized by locals, as if it were a separate state, but that may be simply because it has Western Kentucky University, with a basketball team that occasionally competes on the national scene but is more of an affectionately viewed little brother than a rival to the main University of Kentucky campus.

I had already learned, from a colleague at one of my college summer jobs back home, that Kentuckians do not have a uniform accent. My mom can often pick out people from Hazard, her eastern Kentucky hometown in the coalfields; she can, if she's thinking about it, tell a northern Kentucky resident by the not-quite-Yankee accent. As one born accent-deaf in the big city of Lexington, I normally can't hear these distinctions. Still, though the lesson of my weed field trip was weeds, not speech, I could definitely hear that the people we met as we drove west didn't speak like my mom anymore. If the definition of weeds applies to people, I felt like a weed there—a person out of place with the locals.

At the time, I wasn't entirely confident in my plant identification skills. In undergraduate plant taxonomy class, we'd focused on flowers — counting petals and sex organs — to determine family classification. In lab, we learned about floral families from glass models, with stern docents glaring and reminding us repeatedly not to lean on the desklike cases, and from picked, live models purchased by our teaching assistant under a wholesale pass to the Boston Flower Market.

The idea of identifying plants — in the ground and from their leaves only! — was terrifying to me because we'd learned repeatedly not to count on stems and leaves for a definitive plant identification.

And here I was, far closer to home than when at Harvard but much farther from my comfort zone, being told that by the time a weed flowered in a crop field, it was too late to bother identifying it. By then, it probably had neighboring siblings gone to seed, and the weed would already have stolen considerable light, water, and nutrients from the accompanying crop. Besides, one has to identify weeds early—even when the only visible leaves are the two newborn leaves that have unfolded directly from the seed—because that way the correct herbicide can be chosen to control the weed you've identified.

Identifying plants from their seed leaves is somewhat like trying to figure out which grandparent a newborn infant looks like in the first hour after birth, when the baby's face is still blotchy and misshapen. For example, clover, which has a perfectly recognizable water-drop-shaped three-parted leaflet even on an adolescent plant, bears tiny, kidney-shaped seed leaves and a so-called "flag leaf" next that is single and almost circular. Velvetleaf, which has large, fuzzy, spade-shaped adult leaves, bears seed leaves that are small, hairless, and heart shaped. For this initiation weeds tour and for weeks afterward, I was stunned at the idea that all these people around me could identify plants at the seed leaf stage; I felt that my whole education in plant identification had been a big, expensive joke. Within three months, I could match flowers and seed leaves reasonably well, but for that whole trip I was trying desperately to make sense of what I knew in the context of corn and soybean fields, a largely unfamiliar landscape.

I was sure my advisor-to-be, Bill Witt, was testing me when he asked about a low-growing weed next to the field. The only euphorbia I'd seen was poinsettia in flower, and the little paired lines of tiny oval leaves didn't look at all like poinsettia, so that was the furthest from my mind. The leaf arrangement looked more like what I remembered of the pea and bean family, so I mentioned this, and said why, hoping that I could get credit for my logic if not my accuracy. Finally, I picked a leaf, and a tiny bit of milky sap came out, puzzling me to no end. I finally said that I knew euphorbia produced milky sap, but I still thought this looked like a pea. He said, I remember, "Interesting . . ." and I knew then that he was not going to answer for me, and also that he was watching what a strange puzzle I was as much as he was trying to find out if I knew any weeds. At that time, I definitely didn't know any, and I am still embarrassed when I think of that moment: me acting as if I knew all about plant identification when I clearly knew, and still know, only a fraction of the weeds Dr. Witt does.

I quickly learned better than to grab a horse nettle—tomato's spiny, weedy cousin. The other weed science professor, J. D. Green, grabbed a johnsongrass plant, intending to pull it up for us, and let it go with a howl when it gave him a bloody, deep paper cut. You might recall from chapter one that johnsongrass is illegal in my current township, but it isn't because of its potential for paper cuts. While Dr. Green took himself to the hospital for stitches, Dr. Witt explained about johnsongrass's toxicity to cattle, despite being brought to the United States as potential cattle forage. This tidbit was the first of many examples I learned of potentially useful plants turning out, instead, to be weed problems. This whole situation was frightening, not only because of the bloodshed, but because I was beginning to realize that identifying a plant as belonging to the grass family was not going to be useful in weed science. I had yet to learn the first thing about distinguishing one grass from another.

If I had a lot to learn about weed identification, I also had a lot to learn about the culture of academic weed science and even about the culture of my home state. This trip was my introduction to the seeming luxury that awaited me if I chose to work in the agriculture industry. First, I was the only woman on the trip; even today, women constitute just 13 percent of the membership of the Agronomy Society. Second, the trip itself was like a trip through a foreign land. Though I'd just finished four years living in dorms at Harvard, I'd rarely stayed at a hotel as fancy as the one we stayed in, as my parents almost never stayed in hotels. I'd never eaten burgoo, a well-known Kentucky meat stew (native versions contain squirrel meat and supposedly even brain with buckshot seasoning, but the restaurant version we ate in Henderson, Kentucky, contained only commercially raised meats), because we never went to fancy restaurants when I was growing up. I know now that nice meals and high-class hotels are normal amenities for any travel on the corporate dime, but they looked luxurious to me at the time. I enjoyed the situation, but I also felt out of place.

Later, in August, my other advisor, Larry Grabau, a sustainable agriculture researcher, invited me to collect data and identify weeds in soybean fields scattered across central and western Kentucky. We visited fields belonging to twenty different farmers, all of whom had consented to help us test how well soybeans from more northern climates might do in Kentucky. (This was the trip where I met may-pop passionflower, which I discuss more in the morning glory chapter.) Armed with two thick three-ring binders of weed identification sheets from the Weed Science Society, I learned weed identification by immersion, the way an exchange student learns a foreign language. At the same time, I stumbled through many fields with those heavy phrasebooks before, by the twentieth farm, I could keep them in the van and return for them only to double-check when we were done with the whole field.

Both trips were excellent primers for weed identification class, because by the end of the summer, I knew that by taking plant taxonomy I'd only just begun to become a weed scientist. In plant taxonomy, we learned about families of plants—many in a single lecture—and about general characteristics, mostly of flowers, that were common primarily to members of these families. On exams, we never even had to identify the genus of the plant—thank goodness, because getting the family right was hard enough. I loved that class and studied regularly for it, and I still squeaked out only a B. Weed identification class required a lot of memorization as well, but the scale was smaller. Rather than knowing one hundred families of plants, we learned about a hundred individual plants, their common and Latin names. Prostrate spurge was, mercifully, the only euphorbia and seemed easy as a result, even without horns or milk, now that I knew what to look for: all those traits that had confused me when I embarrassed myself trying to show off to my professor.

Unfortunately, in teaching environmental studies, I don't get to take students on summer weed tours or to look at farm fields. My university was just recently granted a farm, augmenting our thirty-acre campus with a place for field trips and weed science research plots. Still, because I don't teach summer school, plants in my courses are confined to the academic year, and I couldn't fill a course I offered this fall on agricultural plants, despite student reviews from other classes that I'd hoped meant I could attract a willing audience, even of urban women. Weed identification class will clearly have to wait for someone with more legendary status among students. In persuading students to care about plants, flowers remain my primary selling point. The fact that I know my weeds is simply a bonus, a trick that enables me to walk out on a lawn and consistently find a handful of identifiable species.

I do have an opportunity to take students outside for three weeks in May, when we have a short and intense spring term. I get students for hours at a time, enough to take them out to look at woodlands and lawns and nature preserves, with the Northeast Weed Handbook and Newcomb's Flower Guide in hand. Most students stick happily to Newcomb's, with its organization by petal number and leaf arrangement making identification possible. With that book, I can even give partial credit for getting to the right page, because getting that close demonstrates that the student has at least learned the rudimentary searching skills.

But what makes me happiest, in this class, is seeing some students take the extra step of trying to identify a weed that isn't in flower. For this task, Newcomb's cannot help them. While the students are flipping, one by one, through the pages of the Northeast Weed Handbook—arranged by plant family—I remember being the newly resident weed identification expert. For a moment I am transported back to somewhere in Western Kentucky, with a new and striking weed in front of me. I remember the thrill of finding the weed, leafy and flowerless, appear suddenly on its matching page in my guidebooks, and feeling for just a moment that I knew my place. I belonged here — in weed science, in this Kentucky soybean field—among the spurges.

I hope by now that my transplanted friends in Greenville feel equally at home in their soil, with or without the spurge.

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