Humans have been introducing plants to new places for hundreds, if not thousands, of years. Sometimes it’s been on purpose, but often the introductions weren’t planned. Some introductions have served human needs well as food, fiber or for other uses, and not become a pest that we eventually learn to hate. Others, and there are many, have become difficult to control invasive pests that sometimes completely smother out native plant communities. Story County is now home to a fairly long list of alien invaders. What follows is a bit of background on some of our more common invasive plants.


Canada thistle, a perennial weed that nearly everyone but a butterfly loves to hate, came to our shores not from Canada, but from Europe around 1600. Crop seed that immigrants brought with them was often contaminated with weed seeds. People have been fighting it ever since, and, like most hardy weeds, it often defies control and is still thriving. A distant cousin, musk thistle, arrived in America from Eurasia by accident in 1852. A biennial, it spread far and wide via airborne seeds. It didn’t appear in our area until around 1980, and if not controlled, can ruin a pasture in only a few years.


Autumn olive came from Asia in 1830 as an ornamental. It began to be promoted as a good wildlife habitat plant in the late 1960s. Many of us in the conservation field were suckered into planting it, but it didn’t take long to show its less friendly side. Its pale yellow flowers in early summer are heavily fragrant and birds love to gobble up the red fruit later in the year. They have spread the seeds far and wide. It has virtually taken over the understory of wooded areas at Hickory Grove Park where I, sadly, helped plant lots of it. Its cousin, the Russian olive, came from Eurasia around 1900 as an ornamental. It’s not as aggressive here as the autumn olive, but in drier parts of the west it has taken over vast areas.


Common buckthorn came from Europe and western Asia in the early 1800s also as an ornamental tree. Although it’s nearly black fruit is extremely bitter to people (I’ve tasted it), birds like it just fine and continue to spread its seed into woodlands. It began to be an invasive tree in our area woodlands in the 1980s. Some understory areas now have little else growing in them. Another woodland invader that gives even buckthorn a run for its money is the Asian honeysuckle. It, too, can take over the understory of a woodland; choking out almost everything else as it does so. A couple of varieties arrived in America in the 1800s as popular ornamental plants, with their pink-and-white flowers and red fruits. It was promoted as a wildlife habitat plant in the middle 1900s and I, along with hundreds of my peers, planted it extensively. It’s still hard to forgive myself for that.


It wouldn’t be so bad if I didn’t have to forgive myself for planting multiflora rose, too. It was also promoted as a wildlife plant, and I first planted some as a Boy Scout around 1960. It came from eastern Asia in the late 1700s as an ornamental and as a living fence. It was, and maybe still is, used as a hardy root stock to graft under fancy roses. Like so many other invasive plants, birds relished the little rose hips that followed the flowers and spread their seeds everywhere.


Garlic mustard didn’t arrive in our area woodlands until late in the 1900s and didn’t develop heavy infestations until around 2000. Unlike most invasive plants, it came from Europe in 1868 for use as a food plant. I have eaten it as a cooked green and as pesto and it’s not bad. Unfortunately, this rather weak-appearing, shade-loving annual plant is a heavy seed producer. Left uncontrolled for only a few years, it can grow into patches so dense that no native wildflowers can survive. I have pulled it by the truck load, sprayed it, and even helped to conduct a late fall burn in a heavily infested Illinois woodland where my daughter used to work. The seed sprouts in the fall and can be killed by a well-timed burn. The seed moves around on hiker’s boots, bike tires and even stuck to deer hooves. It can grow to three feet or more in height, but even a few little hard-to-spot three-inch plants with only a few flowers will make enough seed to keep a patch going.


These invasive plants have a couple of things in common. They can all severely damage native plant communities. They are all tenacious survivors, as well. We may talk about eradicating them, but the best we can hope for (if we are persistent enough) is to keep them under control.


Steve Lekwa is a former director of Story County Conservation.