Central Pennsylvania roadsides, meadows and stream bottoms are alive with the color and scent of Dames rocket a very common late spring, pink and white wildflower. The pastel colors and pleasing perfume that Dames rocket adds to the countryside are some of the things that I enjoy about May.
However, that enjoyment is coming to an end there is just too much of what I once thought to be a good thing.
When I was a youngster growing up in Bedford County in the 1950s, Dames rocket (Hesperis matronalis) was rare. I remember that my father transplanted some into the roadside ditch near our home so that we could enjoy its color and fragrance. After the timber was cut from my Grandmothers farm, I was amazed to see how Dames rocket took over the disturbed forest.
When I moved to Centre County in 1979, there was little Dames rocket in the Bald Eagle Valley. Now, it seems to be everywhere not just a plant here and there, but thick stands of it.
Dames rocket grows one to three feet tall, and has white, purple or various shades of pink flowers. Some plants even sport variegated white and pink petals. It has pointy alternate leaves that have saw-toothed edges. A more specific botanical description is hardly necessary because you cannot miss the flower at this time of year.
Dames rocket was likely brought to America from Europe by the colonists during the 1600s. Many people mistakenly call Dames rocket phlox. Dames rocket is an invasive alien plant that looks like several plants native to Pennsylvania garden phlox, smooth phlox and wild sweet-William. However, closer inspection shows that Dames rocket flowers have only four petals, while the others all have five. Wild sweet-William and phlox species also bloom later in the summer, rather than during May.
Well-known ecologist Steven Apfelbaum has recently sounded the alarm about Dames rocket after witnessing its explosive growth in his home state of Wisconsin. Apfelbaum, the founder of Applied Ecological Services, Inc., and the co-author of the Restoring Ecological Health to Your Land series, is concerned about the long-term impact of Dames rocket.
Left unchecked, this beautiful, yet lethal plant will wreak havoc on the natural environment, threatening the survival of native plants and degrading habitat and water quality, Apfelbaum wrote in his alert.
Dames rocket produces an abundant number of seeds that become attached to the fur of passing animals and thus are easily spread. The plants seeds are included in some commercial wildflower mixes and it is often transplanted by humans who appreciate its beauty, but do not realize the danger.
As a result, the plant is rapidly infiltrating stream courses, wetland margins, farm fence rows and tree lines. It is even colonizing natural areas of prairie and savanna, Apfelbaum said. Dames rocket seems to be following explosive growth patterns similar to its close relatives in the mustard family garlic mustard, yellow rocket, hedge mustard and wild radish all highly invasive species that have infested agricultural lands and native woodlands, savannas and grasslands across the country, he noted.
Other invasive plant species that have been identified as problems here in Pennsylvania include Japanese knotweed and purple loosestrife.
Apfelbaum cited a report from the General Accounting Office, claiming that invasive species cause about $200 billion per year in damage in the United States. According to Apfelbaum, that report did not include Dames rocket, garlic mustard and others, so the real figure is likely much higher.
Apfelbaum suggests that this plant might have the ability to produce chemicals that reduce the growth of competing plants. However, research has not yet been carried out to confirm whether such chemical warfare characteristics exist.
Dames rocket appears to have allelopathic tendencies similar to garlic mustard, a close relative, he said. Observations in floodplain forests have shown nearly continuous development of Dames rocket along with an equally dense growth of garlic mustard both plants are able to quickly form dense monocultures within a few years of colonization.
On our Centre County property, my wife and I had several nice, self-seeding populations of sweet Williams at various locations, but this year Dames Rocket has invaded those areas and the sweet Williams are almost nonexistent. Apfelbaum suggested that some plants, possibly sweet Williams, are more susceptible to the chemicals than others.
During the past five to 10 years in my home area of southern Wisconsin, Dames rocket has hit an accelerated level of colonization. It is absolutely doubling itself every year, Apfelbaum noted in a phone interview. What we are seeing in the moist, fertile soils is that it can completely dominate the understory of a floodplain forest.
It appears that we are now seeing the same thing in Pennsylvania. Ecological Services biologist Scott Quitel, who works out of their Philadelphia office, agrees.
I was working in western and central Pennsylvania last week, and I was really impressed as to how invasive Dames rocket is becoming in the state, Quitel said.
Dames rocket is an alien plant, but has it found a place in our ecology? Apfelbaum thinks not.
Butterflies will alight on the flowers, but I never see them exhibiting the same feeding behavior that they they do on favored native flowers, he said. I never see indications that anything is feeding on Dames rockets leaves, either.
Apfelbaum recommends immediate control of the plant where possible.
Controlling Dames rocket is not easy. In moist soils, simply pulling the plant removes it from the ground, roots and all, he said. In slightly drier conditions, pulling the plant will cause the flowering stems to break off above ground level, leaving roots to regrow. Mowing curtails seed development, but some plants have been observed to re-flower and produce seed after mowing.
Of course, herbicides such as Roundup will work, but overspray can kill desirable plants, as well. Sometimes manual control by pulling is the best and least expensive option.
Remember, as beautiful as Dames rocket may appear, it is an invasive species with the potential to damage entire natural ecosystems, Apfelbaum advised. Take action now to defend your environment.
I have been taking Apfelbaums advice to heart. During the past week, I have been busy pulling up as much of the Dames Rocket on our property as I can get to there are hundreds of plants. And to think, just a few years ago, there were none that is the definition of invasive.
Mark Nale, who lives in the Bald Eagle Valley, is a member of the PA Outdoor Writers Association. He can be reached at MarkAngler@aol.com.