Roots and Shoots: What’s Lurking in Your Garden?

Early detection, rapid response

By Pamela Doan

At a recent talk, Current and Emerging Threats in the Hudson Valley, at the New York Botanical Garden’s Invasive Species Summit, the news for recovering natural areas with native plants was not hopeful. On the invasion curve, a standard graph used commonly in the industry to determine the level of infestation through three phases, the Hudson Highlands fall in the “too late” category, meaning that eradication is not possible. Local controls and management are the only recourse to try to control the spread and protect high value areas.

The most prolific invasive plants are Japanese barberry, tree of heaven, mugwort, Oriental bittersweet, Japanese stiltgrass, and the aquatic dwellers water chestnut and phragmites. It’s hard to go far without finding large patches of any of them. I can look out my window right now and see all except water chestnut and phragmites.

Linda Rohleder, who leads the land stewardship program for the New York/New Jersey Trail Conference and is the program coordinator of the Lower Hudson Valley Partnership for Regional Invasive Species Management (PRISM), has trained and sent out more than 300 volunteers who have mapped over 1,000 miles of trails for invasive plants.

“There is virtually no untouched location in our region except for maybe a concrete parking lot,” Rohleder said. “There are widespread invasive species throughout the region, the state, and neighboring states. They threaten our forests, crops, water, water quality and human health.”

As far as Rohleder is concerned, the place to put energy into right now is the new and emerging threats. The refrain is always “early detection, rapid response” for anyone who manages land or works in conservation or ecology. Be on the lookout for the threat and act quickly before you hit phase 3 on the invasion scale and it’s too late. If an invasion is found when it is first escaping into the wild, there’s a much better chance of eradicating it.

On the invasion curve, public awareness comes right before the “too late” phase, when the plants are so prolific they are impossible to ignore. That part of the curve can change, though. Someone hiking or being curious about a new plant in the yard finds many invasive plants. Citizen science through the iMapInvasives app for smartphones ( is helping to identify and control invasive species.

Rohleder mentioned all of the following plants as high risk and all have been found in our area. They have been identified in small numbers for the moment, though, and are currently considered to be manageable. Emerging threats include:

Phellodendron amurense or Amur corktree — This large tree is planted as an ornamental species and its compound leaves look similar to the ash tree but it has distinctive ridged, corky bark. It is one of New York’s prohibited invasive species as of this year, but it has already escaped into forest areas and is establishing itself and taking over. There are three reports of Amur corktree populations in the Bronx and Westchester.

Actinidia polygama silver vine kiwi and Actinidia arguta hardy kiwi are both promoted as an edible fruit that you can plant in your yard. Both are woody vines. Rohleder called it worse than Oriental bittersweet. “We can still do something about this if we can stop people from planting it,” she said. “It is definitely moving by seed but we’re not sure how yet. It’s being studied.” Both hardy kiwi and silver vine kiwi have been found locally.

Viburnum dilatatum or linden viburnum — This invader is still being sold in New York but don’t plant it. It escapes cultivation and there are great native viburnum alternatives.

Ficaria verna or fig buttercup or lesser celandine — This spring flowering perennial looks similar to marsh marigold, a native plant, but it quickly takes over anywhere it can establish.

Arthraxon hispidus or small carpetgrass — This 18-inch, grassy plant prefers sunny, moist areas. So far one population has been found in New York in our neighboring county, Westchester. It was probably found in soil or fill and then seeds spread.

This isn’t just a moment for the native plants that are displaced and lost; it’s the death of an ecosystem. The flora and fauna evolved together for a reason and are all interconnected. Research demonstrates over and over that each little vector is impacted. Get to know the plants and trees you see every day. Find something unusual? Log it into iMapInvasives.

Photo by Leslie J. Mehrhoff, University of Connecticut /

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