© Marlene A. Condon
June, 2015
As April transitioned into May, I was surprised to see a fair number of daffodils still blooming along the roadway where I walk. It was a sign of how chilly the spring had been.
Another sign I picked up on that morning was the “invasiveness” of daffodils. There were many, many daffodil clumps spanning the miles of my exercise route. They exemplified the ability of some plants brought to this country to reproduce successfully enough to move well beyond the garden gate and out into the larger world.
Such so-called invasive plants have constituted an issue for some time now, although I don’t recall ever hearing anyone complain about the invasive nature of daffodils. Perhaps if a plant is lovely, people can forgive its tendency to reproduce and spread.
But when you are talking about the health of our environment, you can’t entertain such biases. If a plant meets the criteria for being considered “bad,” then it shouldn’t be granted a special exemption.
This situation begs the question, “Should nonnative plants be considered pestiferous when they spread?” I say absolutely not in most cases, especially in back yards, along hiking trails, in meadows and fields, and by roadsides. These plants are providing an invaluable service to a degraded environment.
Usually nonnative plants fill an area only after it had been left barren because of an altered soil profile brought about by man, severe storms, or both. Very few native plant species can grow in poor-quality soil.
By moving into these damaged areas, alien plants do what humans can’t easily do: they rehabilitate the soil. In other words, they are creating a rich soil so that—once they’ve done their job—native plants may again be able to grow there.
Nonnative species are able to obtain nutrients from nutrient-poor soil and transform them into plant tissue. When that plant tissue is returned to the soil (such as when leaves detach to be replaced by new ones or when the plant itself dies), it becomes humus—organic material that enriches the clay soil because its nutrients are in a form that’s usable by many more kinds of plants.
But enriching the soil is not the only thing invasive plants are doing for the environment. They are also supporting our wildlife, all of which require plants for food, shelter, and nesting sites. Every plant on invasive-species lists provides one or more of these basic necessities to our critters.
Although “invasive” plants are often referred to as noxious (deadly, harmful, dangerous), they are simply doing what they are meant to do—reproduce and multiply if there is room for them and the growing conditions are right. It’s what “happy” plants do.
Consider Japanese Knotweed (Fallopia japonica), a large herbaceous perennial plant that was brought from Asia to this country in the late 1800s. Its flowers feed abundant numbers of insects, especially bees of many kinds.
Yet according to the National Invasive Species Information Center, this plant is problematic because “it crowds out native species.” Well, yes, Japanese Knotweed eventually gets large enough and spreads enough to take up space so nothing else can share the space, but in all likelihood, this plant is not crowding out native species, but rather, other nonnative plants like itself!
One of the reasons this plant was originally brought to this country was erosion control after the ground had been denuded by man’s activities, such as road building. The only reason to bring in a foreign plant to prevent soil from washing away in these areas during rain storms is because no native plant could possibly handle the job.
During construction, heavy equipment clears away topsoil that native plants have evolved to grow in. The subsoil that remains is hard, and made harder still by the heavy equipment driven over it. It takes a tough plant to grow in heavy, hard-as-rock dirt!
In Charlottesville, the City Council recently voted to continue to use pesticides for controlling unwanted plant growth, such as Japanese Knotweed growing along the Rivanna River. People believe the plant “will take over next to streams so nothing else can grow there,” creating “a monoculture.”
However, it could well be that nothing else can grow there. The Rivanna runs red every time there’s a heavy rain. That color signifies sub-soil erosion, the result of development upstream and properties on which land has been cleared right to the edges of streams (it’s allowed on “pasture” in Albemarle County).
Although that soil is traveling towards the Chesapeake Bay and is a major contributor to its impaired state, some of it gets deposited along the edges of the waterways. This red clay is not typically conducive to native-plant growth, which is why nonnative plants were able to start growing in the first place and to subsequently “take over.”
Although one might think the land along the river is in a pristine state, it’s easy to discern the truth of the matter by simply examining what plants are growing with the Japanese Knotweed. If you see many so-called invasive species, such as Japanese Honeysuckle (Lonicera japonica), Garlic Mustard (Alliaria petiolata), Japanese Stiltgrass (Microstegium vimineum), and Autumn Olive (Eleagnus umbellata), that’s an undeniable sign of disturbance.
Killing and then replacing the Japanese Knotweed plants along the Rivanna River will simply re-disturb the soil, setting back the clock for its rehabilitation. If people truly want to help the environment, they need to take the long view.
Over time, the Japanese Knotweed will ultimately be shaded out by trees because Mother Nature’s goal is to create forest. No environment is static; it’s constantly in a state of flux.
People can spend time, effort, and money to remove nonnative species that are able to grow vigorously in disturbed areas of our making, but it’s virtually impossible to do so without re-creating the conditions that brought about the problem originally.
In the majority of situations, it’s difficult to make right what man has done wrong. Better to take the passive approach and let Mother Nature perform the renovations.
In fact, the whole invasive-plant issue has been a huge disaster for our environment. As a result of the rush to judgment that says all of these plants are “bad,” no matter what, herbicide usage has increased tremendously. Even most environmentalists now consider the employment of pesticides acceptable.
It’s as if poisoning the Earth is far better than allowing plants to exist in areas where they are not native. Rachel Carson’s ashes must be whirling in her grave.
This scientist, by recognizing the dangers of pesticides, brought about the environmental movement in which people began to recognize the effects of their actions upon the planet.
Yet now these poisons (substances that are capable of causing illness or the death of a living organism when introduced or absorbed into its system) are seen as either totally innocuous or a choice that is preferable to the alternative.
What is the alternative? The alternative is that a nonnative plant should occupy a spot of ground that in most cases is degraded and incapable of supporting a native plant anyway.
Herbicides sicken and kill many kinds of organisms, either directly or indirectly. Alien plants, on the other hand, often do far more good than harm to the environment. Can there really be any doubt about which choice is the better one to make?