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Bittersweet wreaths can spread an invasive species

Alexander Sinn • Oct 12, 2018 at 1:00 PM

Bright-red bittersweet wreaths are a sign of the holiday season. They also have the power to strangle and bring down a fully grown tree.

Ottawa County Parks & Recreation advises against displaying the wreaths, most of which are made from the non-native invasive oriental bittersweet plant that is taking a toll on the natural habitat.

When used for outdoor decorations or disposed of in compost heaps, birds eat the bittersweet berries but cannot fully digest them. When they dispose of the partially digested berries, the plant is spread.

The oriental bittersweet has flourished at several county parks, including Bur Oak Landing, Eastmanville Bayou and Riverside Park, displacing native plants and wrapping itself around trees. The problem led the county in 2014 to launch the Prescribed Browsing Project, recruiting goats to chomp through the bittersweet so volunteers could remove it.

“There was so much of it that traditional treatment would have been extremely costly and difficult,” county parks spokeswoman Jessica VanGinhoven said.

The goats, including several recently born kids, were sent to Riverside Park in Robinson Township this past spring. Multiple years of goat-chomping are necessary to fight back the existing growth, VanGinhoven said.

A partnership with Allendale Public Schools at Eastmanville Bayou has finally led to some progress, she said.

“What is amazing is that, after five years of work, trout lily and bloodroot began growing and blooming last spring in areas that had previously been completely overrun with invasive plants like oriental bittersweet and garlic mustard,” VanGinhoven said of the progress at Eastmanville Bayou.

While the American bittersweet is considered a threatened species, there has only been one plant recorded in Ottawa County, and it has flowered once every five years as the oriental variety has thrived.

Yard waste

While raking and bagging leaves this fall, keep in mind that yard waste is the leading source of invasive species in natural areas, according to Ottawa County Parks.

Garlic mustard, Japanese knotweed and dead nettle are among many invasive plants that arrive in natural areas from yard waste.

Dumping yard waste piles into natural land can damage the environment, and is prohibited on county land. Piles take years to decompose, smother and kill plants they cover and introduce invasive plants, pests, chemicals and excess heat into the natural community.

In the city of Grand Haven, yard waste drop-off is available each Saturday for city residents starting this month through Dec. 8. Drop-off sites are Griffin Elementary School and Lakeshore Middle School.

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