Thistle

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February, Pittsburgh, with flashbacks to a june long ago in lexington

Since fall, I have watched the little prickly rosettes of thistle leaves sprouting in the lawn near our front flower bed. In February, through several snow thaws, I step past these little patches of spiny green, consider finding a spade to dig them out, but always put it off. A few leaves, not a stem in sight—the baby thistle seems so harmless that it hardly seems worth going to search through the garden tools for such a tiny weed. At this time of year, it isn't even growing. For at least four months now, I have consistently put off the decision: do I let the thistle live, or not?

Few weeds are more universally detested than thistle, even by people who don't know what name to curse it by. A friend from Minnesota described it as "one that has prickers on it, that's low growing. What's that one called? I hate that one—it's the one I always step on when I'm barefoot." And that's thistle in winter, just waiting for the first spring day when the unsuspecting will take the shoes off their tender spring feet to feel the soft grass. That's when it sticks them. Worse, thistle is not just one species, but many. The one that sticks your foot in winter may not be the same thistle that invades your garden in summer.

I have definitely had my battles with thistle. The summer I spent at the University of Kentucky research farm hoeing a third of an acre of soybean, I remember a particular Canada thistle that I could not pull. I believe the first time I tried without gloves, grabbing the base of the stalk, where many spiny weeds are a bit smoother. Cursing, I attempted next with gloves, but the cotton gloves I had at the time did nothing to protect me. Next time I brought rawhide gloves, which worked fine for protecting my hands, but by then the plant was tall enough that I still got poked in the arm, through my sleeves. I discovered the root was too deep to pull completely. Other times, when I had the hoe, I attempted to simply bludgeon the plant to death, even knowing logically that I couldn't kill the root. In some primitive part of my brain, I think I believed that if I was violent enough with the stalk the root wouldn't dare send any more shoots. Between the sore muscles and the spines, I have no question that that thistle plant won the war, and war it definitely was.

I don't always have it in for thistle. Our first summer with our garden, we let many plants grow, simply from not being certain what they were. One we recognized as a thistle, but as we didn't yet know the species, we let it grow. This thistle grew strong and vigorously from early summer, as only a perennial can, so we knew that the previous homeowners had at least tolerated, if not encouraged, its growth. Whatever my feelings about these folks' décor or their dog, I came to trust their gardening. The garden we inherited is diverse and flowers across the seasons. We let the thistle grow, warily.

The experience was actually quite rewarding. While the plant prevented us from casual gardening within a two-foot radius, it also bloomed prolifically, and it fed a number of butterflies that summer. I particularly admired that it not only offered food for butterflies but protected them from the grabby mitts of our daughters, who consistently try to catch butterflies dining on less prickly garden flora. The flowers were also beautiful. Thistle blossoms are a sign of hospitality. One is featured in the signature logo of MacKenzie-Childs, an exclusive Alice-in-Wonderland-style decorating store from upstate New York just a few miles from the Cornell weed plots. By that ironic standard, our garden that year was terrifically hospitable.

Thistle species are distinguishable by the size of the blooms and a few other fairly subtle features of the leaves and prickles. Canada thistle (Cirsium arvense) is perennial, rather than biennial, and this species is particularly undesirable for a couple of reasons. One is that the plant is capable of surviving many attacks with a hoe—trust me—because its underground stems help the plant both spread and store nutrients for regrowth after grazing or hoeing. Also, Canada thistle flowers are too small to compensate us with beauty for the pain of keeping it around. The biennial species, such as bull thistle (Cirsium vulgare), can easily be killed in its first season, when it is a nonflowering, prickly rosette of leaves. However, if we leave the bull thistle, it rewards us richly with large purple (or yellow, for Cirsium horridulum) blooms that attract both common and rare butterflies.

All weeds have seasons in which they can be controlled easily, and other times when they are noticeable. For thistles, farmers are often tempted to spray them when they see flowers, but in reality, the flowering thistle is already at the end of its two-year lifespan. Although the farmer may have a shot at keeping those thistles from going to seed, most of the "damage" has already been done. Also, weed seeds have a way of lasting long enough so that one good year of control is never enough. Some of these notable overwintering weeds include thistles (bull thistle, musk thistle), teasel (like thistle, but with supercharged prickles), and common mullein (broad, soft leaves, later graced by a four-foot spike of yellow flowers). These are the weeds that give us the luxury and temptation of deciding our values on weeds. I notice new thistle rosettes in fall with some happiness—butterflies love them, and my children won't pick them. What could be better? But over the months, temptation arises: wouldn't it be nice not to have to worry about the girls' bare feet, or about gardening with gloves in that bed? In winter, pulling the thistle once at this stage is probably enough to kill it, and with such minimal effort, especially since I already have the gloves on against the cold. If I just got out the spade for a minute of effort, I could be certain of easy victory. For some thistles, I do, and they are gone forever. The decision is so irrevocable that I always try to leave one spare, tucked somewhere a bit out of the way in the garden.

Goats, in children's literature, are famous for eating thistles readily. In fact, many plants that cows find distasteful are manna for sheep or goats. One of the great losses of our single-species animal pastures is that more plants are considered "weeds" which might otherwise be called "forage." Pasture researchers know well the benefits of mixed pasturing—sheep and cattle, for example—because less effort is needed by the farmer to maintain a healthy plant balance. Cattle manure, left behind in large patties, is a wonderful place for the germination of thistles and other tall-growing broadleaf plants, and in the absence of other grazers the cow pies become havens for weeds. Sheep and goat manure, falling in smaller, drier pellets, is more conducive for acting as grass fertilizer, for feeding cattle. Thistles are a greater problem now that fewer farmers keep small livestock. Both the thistles and the small livestock would, if they could, make a good lobby for one another, and for the kinds of smaller, diverse farms we intuitively prefer. Why else would children's toy farm sets include cows, pigs, sheep, horses, chickens, and a dog?

Consider this the next time you see a beautiful, smiling model in a magazine with a milk mustache: she's not advertising goat milk. And when we hear ads promoting "Pork, The Other White Meat," or "Beef, It's What's For Dinner" — all are encouraging us to forget that our meat sources were once more diverse. These ads support the near monopoly market on meat animals by companies such as Car-gill and Archer Daniels Midland. And though I'll leave the discussion on the topic of meat production to writers who've researched the subject more, such as Barbara Kingsolver, Michael Pollan, and Eric Schlosser, I'll add just one tidbit: if we raised a variety of meat animals, they could eat a wider variety of plants, including some that are, for cattlemen, rangeland and pasture weeds.

One weed-control method that has been proposed for use against rangeland thistles is biological control. For thistles, biological control means, as one example, introducing a weevil that consumes the blooming head, preventing seed production. Ecology researcher Dan Simberloff, however, has noted in a number of academic papers and talks that we have no idea if the weevils we would like to introduce might prefer, instead, to control some of our rare, native thistles, rather than the weedy rangeland thistles that are widespread and available. The history of biological control is a mix of divinity and despair, with brilliant success stories matched by any number of glorious and miserable failures. Many of these incredible failures took place on islands, such as Australia's cane toad, the subject of a nearly cult-status documentary, The Cane Toad Movie. The cane toad, one scientist notes in the film, was introduced to control the sugar cane grub, but, it turns out, their life cycles don't intersect at all — the toads will spread seemingly anywhere in Queensland except into a field of sugar cane. The failures of biological control have resulted primarily from a lack of research on potential side effects for native species.

Throughout grad school, I always wanted to believe that if we were inventive, we could figure out how to use biologically sensible methods to combat weeds. Biological control, I knew, was effective for a number of insect problems. I wanted it to work on weeds, to make my knee-jerk opposition to herbicides easy to manage. For example, I wish that the turquoise mold that grows on dead poison ivy in my yard could be applied to live poison ivy to kill it. For a number of reasons, though, biological control remains a fairly fringe movement in weed control circles, limited primarily to researchers working on rangeland—areas that were vast but relatively unproductive, acres not economically worthwhile to pass over individually even with a tractor-sprayer. After I heard Simberloff speak at Cornell for an ecology department seminar, I realized that biological control should remain a limited way to reduce weeds, in part because of the risks of the wrong species being controlled.

At the community center near our house, the bulb garden we planted at my daughter's sixth birthday party made the space look habitable enough that they put down a load of mulch there. Mulch can be a way to suppress weeds, but of course, if the mulch is made from weedy plant material, weed seeds may actually be dispersed wherever the mulch is spread. After mulching, the garden space looked much better, and I was inspired to add a couple of chrysanthemums when I planted some in our own gardens. The next year, though, the entire space erupted in Canada thistle. I suspect thistle seed was mixed in with the mulch, but perhaps the thistle seed was already present, and the mulch helped it thrive. I'll never know for certain how it happened, but by the time I saw it, the thistle was as thick and regular as any good field crop.

This is a garden that I usually tend opportunistically when my daughters are playing on a nearby playground. I never have been much interested in simply playing with them—I much prefer to be a busy nearby presence while they entertain themselves. The thistle infestation annoyed me because I knew that pulling them would require strong gloves, and that even with the gloves, the thistle would grow back. I remembered all too well the thistle in my research plot, and I dreaded that battle.

I ended up asking permission to use an herbicide, and even then removal wasn't painless. A week after spraying, I went in with gloves and long sleeves and started pulling. I was uneasy with the whole process, even with the management's blessing, and I wanted the thistle gone before death was complete and obvious. So when a dad dropping his son off for soccer practice stopped to talk to me, I was certain I was going to have to defend the herbicide use. Instead, he warned me that thistle would come back if I just pulled it. He was right, as I know, because in the places where I had sprayed less, trying to avoid killing flowers, the thistle has come back. At the time, though, I was so relieved that I ended up chatting with him for twenty minutes about thistle and herbicides and lawn care. I wasn't in trouble after all.

In the end, that conversation was the only one I had on the subject. I had the distinct impression that people feared if they spoke to me I would ask them to help out. No one, except the center director, said thank you. Since then, I have made a real effort to praise gardeners at work in public spaces. We think of them as laborers, but my bet is that quite often they are volunteers. Or maybe we just don't appreciate any plant-related labor enough, volunteer or not.

You might think, what with the growth in the organic food market and the higher price of its produce, that we as a culture appreciate the labor of organic cultivation, or that we might heap praise and dollars on organic landscapers. I don't know how that market is doing in general. When I was trying to find a mower who would come as needed, or even biweekly, without threatening me with town citations, I found one who was recommended by the local Audubon nature center. I asked him about organic landscaping, and his response was that he couldn't advertise the service that way because people expected perfection just like a golf course, just without pesticides. It appears that impossible expectations make the organic landscaping business challenging if not impossible.

Organic removal of Canada thistle at the community center might have been possible. It would have required, probably, a thick, impermeable cover. Black plastic might have done the trick, though it is a treatment of last resort in organic circles. Alternatively, I could have gone over and repeatedly pulled it until it died. I didn't have that much patience or virtue in me, and if I had I would have been able to prevent the thistle stand from becoming as thick as it did. I couldn't till the area easily, without destroying the perennial flowers or bulbs in the soil. In the community center's garden, the Canada thistle wasn't worth the price of any more physical effort than it got, because that effort would have gone just as unnoticed.

Biennial thistles, in comparison, are a welcome sight. We can keep them or dig them up, but we have plenty of time to consider our options. With a biennial thistle, we have months to get out the hoe or spade and dig it out, with certainty of victory. The great irony of the biennial thistles is that in our gardens and fields, they build strength in their first year, when they are harmless but to a stray bare foot. At this time, we let them grow and generally fail to notice them. If we see a tall, dead thistle in winter, it has already had its moment of glory. That thistle is brown, prickly, and audaciously standing above the snow, and it seems offensive, but its life is already over, and we cannot harm it by attack with hoes, clippers, herbicides, or axes. And we can be sure that its offspring—all those low-growing, prickly circles in our gardens and lawns—will offer us the chance to make the same choice again, next year. I hope that I manage to keep just enough thistles around, so that each February I, too, can make the same choice again.

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