US: Japanese barberry added to list of harmful plants

If you see a hardy ornamental plant with red jewel berries for sale at a home and garden store, do not be charmed into buying it. The Pennsylvania Department of Agriculture recently added Japanese barberry, or Berberis thunbergii, to its list of harmful plants that cannot be legally sold or cultivated in the state.

It was introduced to the U.S. in the late 1800s and was prized in landscaping for its striking red foliage in fall, but in forests and fields, the prickly shrub forms thickets that crowd out beneficial native plants and can interfere with agriculture. Although the state’s ban on the sale and cultivation of the plant took effect October 8, enforcement will be phased in over two years to give nurseries time to remove it from their inventory.

Amy Jewitt, the invasive species coordinator for the Western Pennsylvania Conservancy, talked about efforts to document and control the spread of Japanese barberry and other pernicious invaders that can take over landscapes and wipe out valuable crops. A study this year estimated invasive species cost the North American economy at least $1.26 trillion between 1960 and 2017.

As its name implies, Japanese barberry is native to Japan, where it poses no environmental issues because it has adapted to live harmoniously with other native plants, insects, and wildlife. However, in Pennsylvania and other states, Japanese barberry is a known invasive species because of its ability to crowd out native vegetation. When native plant species are outcompeted, native insects and wildlife have a limited food supply and the specific types of habitat they require to survive decrease.

In natural areas where Japanese barberry is prevalent, there is more pressure put on native plants by white-tailed deer, because deer do not like to eat Japanese barberry. This reduces the total numbers of native plants living in an area [and also creates] more open space for Japanese barberry to occupy, thus exacerbating and compounding the issue of ecological harm as time goes on.

Japanese barberry spreads two ways: by seed and by rooting from branches that come into contact with the ground. The spread from residential settings into natural areas primarily occurs when birds consume the seeds of barberry and then disperse them.

The Western Pennsylvania Conservancy recently compiled information on native plant alternatives to Japanese barberry, highlighting three specific species based on their berry production and ability to survive in similar growing conditions. They include strawberry bush, common winterberry, and maple-leaf viburnum.

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