In the wild corner of our Littleton, Colorado, farm is a swath of bull thistles. Just common weeds to most suburbanites, worthy of immediate eradication with a sickle and/or herbicides, thistles are among our more successful immigrant plants, found from coast to coast. Admittedly, their purple-pink flowers are not terribly showy and, in most species, their foliage is festooned with spines.
We naturalists, on the other hand, tend to view weeds as non-native wildflowers. Thistles attract a wide variety of pollinators that feast on their nectar and goldfinches that favor their seeds and down, using the latter to line their nests; indeed, since both the seeds and the down are most abundant in mid-late summer, goldfinches nest much later than other songbirds. This afternoon, a squadron of metallic green bees moved among the flower heads and a variety of beetles cruised along their stems, potential prey for the garter snakes that patrol our wild corner. In recent years, lesser goldfinches, common residents of foothill canyons, have been nesting on our property; no doubt, our substantial thistle crop encourages their annual return.
While invasive, non-native plants can have a negative impact on natural ecosystems, most common thistle species do not warrant eradication. Besides, the herbicides used to control such "weeds" generally do more harm than the plants themselves. We intend to keep our thistle garden, which thrives in the semiarid climate of the Front Range urban corridor.
