Researchers have shown through a study published in journal Ecological Restoration that public gardens could be contributing to the growing problem of invasive plants.
Researchers examined the impact nonnative, invasive plants are having on forests with findings suggesting that plants at arboretums and public gardens inadvertently can seed wild areas with nonnative plants. For the study researchers used arboretum at Cincinnati’s Spring Grove Cemetery, which has recorded more than 1,200 species of trees, shrubs, vines and other plants over its 178-year history. The arboretum is home to 26 noteworthy, mature trees known as “champions” for being the largest or best representation of their species, including a national champion September elm tree and an Ohio champion American yellowwood.
While the arboretum is home to many beautiful native plants, including an enormous white oak that was a sapling when the Mayflower dropped anchor in Plymouth Colony, it is also home to some exotic plants that are bearing fruit and seeds capable of being carried by birds or the wind to neighboring woods.
Some exotic plants introduced to people’s yards and gardens will never pose a problem. But others can become invasive.
Scientists involved with the study have documented thousands of native and nonnative plant specimens at Spring Grove in surveys by people such as Kate Nordyke, the cemetery’s former herbarium specialist. Conover now serves in that role as a volunteer, documenting plants to create a record that future scientists can use to study changes in the region’s biodiversity over time.
Nordyke said she was alarmed by how easily some cultivated plants have spread to natural areas.
Conservation technician Drew Goebel at Cincinnati City Parks said one example is the cemetery’s beautiful Amur cork tree, a state-record tree. Its seeds are sprouting in a park adjacent to the cemetery, Parker Woods Nature Preserve.
“There we found a population of 25 mature Amur cork trees. We took core samples and found that the oldest of them was 60 years old. The oldest six trees are male but then a female tree sprouted there and they began to take off,” Goebel said.
And nine years ago, volunteers cleared acres of nonnative, invasive Amur honeysuckle from Cincinnati park’s Buttercup Valley Nature Preserve, creating fertile ground for another invasive species, Higan cherry, to take hold, he said.
“We found a big stand of them — 50 or 60 that we pulled out all at once,” he said.
“The reason we don’t have more of these other invasives showing up is because another dominant invasive, Amur honeysuckle, was introduced in greater numbers and has already taken over that niche,” Goebel said.