Between Urban and Wild: Reflections from Colorado

My Life as a Weed

175 My Life as a Weed The silver-gray plant stands out against the tan- and rustcolored needles of dried autumn grasses. More handsome than showy, it hunkers low to the ground, with stems that radiate from a central crown and sprout paired leaves along their arc. The leaves get their silvery sheen from a pelt of fine hairs, and they taper to points like spearheads, as uniform and neat as an art deco illustration. The flowers are gone now, but they would have risen from the center of the plant on straight leafless stems, each bearing a cluster of white blossoms tinged with green, lavender, or pink. Oxytropis sericea. I admire the plant for a moment as I nudge the point of my shovel against the base of the fountain of stems, tap it downward with my foot, then lever the tool back until I feel the telltale pop of a root being severed. I stuff the plant into the empty feed bag next to me and move on, eyes scanning the ground. I see another plant, similar in size and configuration, although its leaves are more green, less silver. This is Oxytropis lambertii, which flowers in hues of my life as a weed 176 striking purple-rose. I uproot this plant in the same manner as the other and likewise cram it into the bag. Oxytropis is a legume, fixing nitrogen in the soil, helping to make the nutrient available to other plants. The species is native to these parts, providing some of our most reliable summer flower displays: in all but the driest years, the grasslands will be flecked with purple and white. I am, nevertheless , spending this pretty fall afternoon digging the plants out, having been forced to recategorize Oxytropis, on this particular plot of land, from wildflower to weed. The common definition of a weed is a plant that’s not desired or valued where it’s growing, and Oxytropis lives unmolested on other parts of our property. Within this fenced enclosure, though, it’s undesirable because it’s toxic. The common name for Oxytropis, locoweed, sounds like something out of a cornball western movie, but the plants are indeed dangerous. They harbor a toxin called swainsonine, which, when consumed in high enough quantities, causes brain damage in animals. Symptoms of locoism range from stumbling movements to nervousness to seizures: craziness. Like most forms of neurological damage, locoism is permanent . Horses are more susceptible than cattle or sheep, and loco horses, if they don’t die outright, are usually destroyed, since the combination of clumsiness and erratic behavior makes them dangerous. Digging these plants out of our horse pasture hardly seems worthy of angst, then, and as if to demonstrate the legitimacy of my chore, my little bay horse wanders over to where I’m working. Moondo noses the bag, toppling it over. I shoo him away, reset the bag, and return to my digging. When I turn back with a handful of wilting locoweed crowns, he’s knocked the bag over again and has its bottom seam in his teeth. As I watch, he gives his prize a shake, spilling plants my life as a weed 177 out onto the ground, then drops the bag and stands looking at me, as if waiting for praise for a trick well done. • • • Back before the pasture was fenced and the horses arrived, I asked the old rancher south of us whether I needed to worry about locoweed. He barked a laugh and said I didn’t have enough locoweed around to worry about. I valued his judgment but still asked our veterinarian about the risks as well. While he conceded that locoweed is worthy of concern, he didn’t think we would have a problem as long as we managed our pastures. Locoism in horses typically develops only after they eat a lot of Oxytropis, and the plants aren’t very palatable . On overgrazed pastures, however, animals will browse locoweed for lack of anything else to eat, and the conventional wisdom is that the plants induce addiction: once animals consume them, they begin to seek the plants out, even when other food is available. I work at keeping our pastures from getting grazed down too far, fencing off sections if need be, and I’ve watched our horses eat. They don’t seem to have a taste for locoweed, but they could have seasonal preferences I’m not aware of. Swainsonine accumulates in tissues rather than...