SAINT PAUL, Minn. – Ghost hunters and scare seekers will be invading cemeteries all across the state come Halloween, but even in their search for ghosts and ghouls, it seems they still won’t be the most invasive presence around the gravesites that night.
“People have long brought plants to cemeteries, and we’ve learned that some of these plants are invasive,” said Monika Chandler with the Minnesota Department of Agriculture (MDA) noxious and invasive weed program.
While most active cemeteries are well kept and the grass cut short, invasive plant species are not growing and spreading on the grounds themselves, but rather in the wooded areas or fields on the edges of the cemetery that are not always maintained.
“In the case of a plant like Oriental bittersweet, it has fruit containing seed. That fruit is attractive to birds. If somebody leaves an arrangement that has Oriental bittersweet at a cemetery, birds may come in, eat the fruit and then move the seeds to a wooded area nearby,” said Chandler.
The same is true for plants like teasels. One way seeds are spread is by birds.
One historic use of common tansy was to line coffins with it to ward off insects. Tansy seeds could germinate in place or spread with wind or moving water.
“Once we learned that these species were big trouble, they became prohibited noxious weeds” she said. “They would no longer be used in arrangements.”
But the plant species are around, along with many other invasive plants. When people visit places like cemeteries, where invasive plants might reside, it is important that they do not inadvertently carry seeds out of that area.
Both the MDA and the Minnesota Department of Natural Resources (DNR) keep list of invasive plant species. The MDA’s list focuses on those species that are regulated while the DNR’s list is broader and covers any plant that is invasive. The plants on the MDA’s list have gone through an assessment to determine if they need to be regulated.
“We do a risk assessment for each of those species. Then a committee evaluates whether they should be regulated and if so, how,” said Chandler. “Then, the Commissioner of Agriculture makes the decision about whether those species should be regulated.”
All invasive species that the DNR has identified and put on their list have either been or will be assessed by the MDA.
Plants like creeping Charlie, while an invasive species and a challenge for lawn maintenance in some places, is not considered a state-wide threat, therefore is not a regulated noxious weed.
“Plants that are regulated are a species that does economic or ecological harm, or is harmful to people or livestock, like poison hemlock, which can be fatal if ingested, or a species that can harm property,” she said.
It’s not all bad for cemeteries though and it’s not just noxious weeds coming out of them. Old cemeteries, pioneer cemeteries, abandoned cemeteries, and those little cemeteries that are all too common on the sides of Minnesota roads are often a good source for native plant species and varieties that have not been influenced by plant breeding.
“Researchers have looked at these old prairie and pioneer cemeteries and they can find examples of native plants, native grasses and flowering plants that have remained there undisturbed for all these years,” she said.
These old cemeteries are a hunting ground for scientists and researchers studying remnant prairies. The land has remained intact and untouched since the cemetery was last used, which may have been hundreds of years ago, depending on the cemetery.