Invasive species – Part 1
The history of our invasive species is a good read. Many were brought into the United States, on purpose, to solve problems or enhance certain aspects of our life. These early introductions happened before regulations were in place to monitor non-native organisms (those not native to North America) and to study their impact on native species.
Many non-natives never achieve the notoriety of being placed on an invasive list, as many of these organisms exist in equilibrium with our native species. Examples include apples and soybeans, both from Asia. We don’t see these running amok in wild, unmanaged areas of the U.S.
Non-native plants, then, can fall into the invasive category based on their ability to reproduce, spread, and become the dominate player in the surrounding ecosystem. Basically, they outcompete everything else around them for space and nutrients.
A close-to-home example is Japanese knotweed, a perennial plant that dominates the rivers, creek banks, and ditches of central Pennsylvania.
A little bit of history explains its entrance into our country. Many, many decades ago, the gardening community had a great thirst for different, attractive plants for landscapes. A plant explorer brought Japanese knotweed back to England and it eventually made its way to our shores where American gardeners loved it.
Look no further than a U.S. nursery catalog’s description: “A bold, handsome plant 4 to 6 feet tall, with stout clustered stems. Leaves broadly ovate or heart-shaped, bright green. Flowers white, small but very numerous, the great clouds of bloom giving a very soft and pleasing effect.” (pg 124, 1907 Biltmore Nursery Catalog).
Who wouldn’t want that in their backyard?
When I give presentations on an invasive, such as the spotted lanternfly, the question always come up: “Do any of our natives become invasive in other countries?” And the answer is yes. While we seem to be the worldwide leader on number of invasive species that we struggle with, there are a number of our own native animals, plants and insects that are wreaking havoc on other continents. Their stories are just as interesting, and we’ll look at a couple of those examples in my next column.
Tom Butzler is a horticulture educator with the Pennsylvania State University Cooperative Extension Service and may be reached at 570-726-0022.
Some common invasive plants in Central Pennsylvania are listed, along with the reasons they were introduced here:
r Purple loosestrife — Grown for its ornamental value and as a medicinal herb for the treatment of diarrhea, dysentery, bleeding, wounds, ulcers and sores.
r Tree of heaven — An exotic, fast-growing, ornamental shade tree for the gardens of larger home and farm landscapes.
r Multiflora rose — Rootstock for grafted ornamental rose cultivars. Later promoted by U.S. Soil Conservation Service for use in erosion control and as living fences, or natural hedges, to confine livestock
r Garlic mustard — For medicinal purposes and food.