James Bruggers

Louisville Courier Journal

It was so warm in December it seemed as if those buttercup bullies might soon be spreading a blanket of invasive yellow across Cherokee Park bottomlands.

Ranunculus ficaria, or the fig buttercup, forms dense mats and is one of many plants remaking Kentucky and Indiana's landscapes, threatening to replace a variety of native wildflowers including populations of wild geranium, crinkleroot, certain native onions and trillium.

A new mapping tool unveiled last year shows just how invaded Kentucky and Southern Indiana are, according to the U.S. Forest Service, whose researchers developed the database that allows for the map.

The map it has created reveals the portion of the more than 741 million acres of forested land in the United States that has been under assault by aggressive foreign plants. Ours are generally shaded orange, signaling they are between 50 to 80 percent invaded. It appears Kentucky also has some red zones, meaning between 81 and 100 percent are invaded.

“For this study, our intention was to let people see how large data sets can be used to understand macro-scale issues and monitoring forest invasion," said Qinfeng Guo, a study co-author and research ecologist with the Eastern Forest Environmental Threat Assessment Center.

"This broad-scale study gives us a wider perspective that one can’t get from local studies,” he said in an agency write-up of the research, which was published last year in the journal NeoBiota.

The problem in Cherokee Park – which native plant lovers have been battling – is made worse because of all the pavement and buildings in the Beargrass Creek watershed. A lot of the rain that falls in the area gets quickly funneled into the creek, instead of being absorbed into the ground, scraping away topsoil, making it ideal for the buttercup to take over.

In 2010, I took a deep dive into the world of invasive species and reported how foreign plants, animals and bugs often arrived as a result of misguided efforts. Like kudzu. It was endorsed for decades by the federal government to prevent soil erosion – before it became known as "the vine that ate the South" and the subject of eradication programs in Kentucky, Indiana and elsewhere.

Even the Asian bush honeysuckle, perhaps the most pernicious invasive plant in the area, was part of the original plan for Louisville's Olmsted parks. It has been at the center of an expensive and labor intensive removal effort.

"Olmsted wanted dense plantings to allow for a buffer from the outside world," Liz DeHart, spokeswoman for the Olmsted Parks Conservancy in Louisville, told me at the time. "Now we have discovered what some of the negative effects are. It takes over and prevents additional growth of native trees."

Other plants are brought in for commercial sales at nurseries but escape from backyards into forests, such as the smothering vine called porcelain berry. Its turquoise, blue and lavender berries stand out against the green foliage of a lush forest in summer.

We've got it bad in the east, the forest researchers found.

Eastern forests have a higher invasion-intensity – a higher percentage of sample sites containing invasive plants of concern – than far western forests, the researchers found. The difference: 46 percent compared to 11 percent. Hawaii’s forests have the highest invasion-intensity, at 70 percent, and forests in Alaska were tied with the intermountain region (think Utah, Nevada, western Wyoming and southern Idaho) at 6 percent, the lowest invasion-intensity.

Officials in Indiana and Kentucky both track invasive plants but largely rely on volunteer efforts to prevent them from spreading, such as recommending best management practices, organizing invasive species removal crews, and keeping lists of the most evil culprits.

In Kentucky, the Kentucky Exotic Pest Plant Council, Kentucky affiliate of the Southeast Exotic Pest Plant Council, has the responsibility of keeping a list of the most severely invasive plant threats to Kentucky. Its current list can be found online. The Kentucky Division of Forestry also maintains a list on its website of the 10 worst plant threats.

And each year, the Bernheim Arboretum and Research Forest, the Southeast council, and the Environmental Resource Management Center at Northern Kentucky University publish a poster identifying a least wanted plant, along with alternatives.

With spring weather not far away, this is a good time to study up on invasive plants and follow the Kentucky forestry division's advice: Be on the lookout for these plants and avoid planting them in your yard. Instead, look for alternatives that are more forest friendly.

Reporter James Bruggers writes this Watchdog Earth blog. Reach him at (502) 582-4645 and at jbruggers@courier-journal.com.