Tuesday, August 09, 2016

Invasive Species Spotlight: Norway Maple

Guest post by Jacqueline Hyman 

There are many different types of maple trees, and they are often used as ornamental plants because of their attractive leaves. However, the Norway maple (Acer platanoides) is an invasive maple tree that overpowers other native plants and trees.

    The tree is not native and was first introduced to the U.S. in 1756, marketed for its shade, hardiness, and adaptability to adverse conditions, according to Plant Invaders of Mid-Atlantic Natural Areas.  The tree has been reported as invasive throughout northeastern U.S. and in the Pacific Northwest. 

    The plant can grow up to 90 ft. with dark green leaves. They flower bright yellow-green in the spring, and the fruits mature in the summer, according to Plant Invaders.

    The Norway maple is invasive because “while native red maple or silver maple have to deal with specific insects and diseases that are pests, the Norway maple doesn’t, which means that it grows faster and creates more seeds than the native trees do, which means that they can’t compete,” said Todd Bolton, Takoma Park’s city arborist. 

    Although other nonnative trees, such as Japanese maples, are planted in the area, the Norway maples are harder to remove and grow much larger. “Japanese maples are not as hardy, they don’t produce as many sprouts, and they don’t grow to full-size canopy,” Bolton said.

    Many trees are hybridized, Bolton said, in order to display the more desirable qualities. However, these trees reproduce with the original qualities of their parent plants.  “Crimson King is a Norway maple variety that was hybridized so the leaves are red, like the color of a red Japanese maple except that they get full size, about 50 feet tall,” Bolton said. “So somebody buys a Crimson King maple because it looks good and doesn’t realize that actually it’s a Norway maple.”

    Bolton said the trees are not being sold as actively as in previous years, but are now coming from trees that were seeded out as early as 30 years ago. “The main problem now is that they’re growing wild,” Bolton said. “Many of those wild trees in the forests in peoples’ backyards are now Norway maples.”

    Bolton said that in Takoma Park, MD, people wanting to remove trees must replace it as part of receiving a permit. “Now if there was a Norway maple growing in that same place and you were going to build a house,” Bolton said, “you would only have to one half of x replacements, because that tree is not as valuable in the ecosystem.”  The tree is on the city’s list of undesirables because it grows faster and taller than other plants, draining the native plants’ resources.

   “They have become endemic and displaced many of our native plants,” Bolton said.

The  "Invasive Species Spotlight" is a summer blog series focusing on a different plant each week that is a problem for Mid-Atlantic home gardeners.

About the author:
Jacqueline Hyman is a junior journalism and English major at the University of Maryland. She is the editor-in-chief of the Mitzpeh, an independent Jewish newspaper at UMD. In addition, Jacqueline enjoys musical theater, and teaches piano and voice at Guitar Center. She is excited to be interning this summer for the Washington Gardener

Image credit: Crimson King Norway Maple during autumn leaf coloration along Terrace Boulevard in Ewing, NJ. Photo by Famartin (Own work) [CC BY-SA 4.0 (http://creativecommons.org/licenses/by-sa/4.0)], via Wikimedia Commons.

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