Species Highlight: Norway Maple
Updated: Mar 24
Simply put, invasive plant species place threats on their environments that can have disastrous ramifications to both the local wildlife and hardscapes. At David R. Lamb A.S.L.A. we believe in being a part of the movement that works to eradicate invasive species and use responsible horticultural practices to replace them with natives. We view this as an opportunity to educate you, the reader, and the town you may live in on what can be done. We would like to highlight another plant species that has invaded North America: The Norway Maple (Acer Platanoides). This tree can be found as far south as the Carolinas, deep into northern Canada, and on either coast of the continent, let’s talk about it.
What is the Norway Maple?
It may be simplest to describe this tree as a ‘triple threat of density’. The Norway Maple is efficient in its spread and method of overwhelming all species within its range. Its dense canopy will block light to anything trying to integrate below. It has an incredibly thick, superficial root mat which can have ramifications in all settings from rural to urban. Finally, by using the gyrating seed pods that many of you will fondly remember from your childhood, the Norway Maple can achieve broad distribution and spread its seeds far and wide, propagating itself and spreading over more area.
One of the Norway Maple’s many strengths also includes that it very closely resembles the Sugar Maple and due to its similarities will often be ignored or overlooked during surveillance. However, there are some characteristics that one can use to identify either species. The Norway Maple will produce rounded leaf buds that will sprout wide leaves as opposed to the Sugar Maple which sprouts pointed buds and longer leaves. A second distinction can be found by observing the bark of each specimen. Sugar maples will have a shaggy bark at full maturity whereas the Norway Maple will contain a distinct crisscross pattern. The final way to ascertain whether or not you are faced with the invasive or native species is to snap a branch off the outer extremities. If the twig produces a clear sap you are dealing with a Sugar Maple. Should the stem produce a white sap the specimen is most likely a Norway Maple.
(Example of Norway Maple's seed pods and leaves)
The Impact It Brings And What Can We Do?
An invader by any other name, the norway maple takes a multi-pronged approach to its spread. I can achieve dominance by choking out the local flora, hoarding forest floor real estate, and surviving in less than optimal environments. For example, in terms of hardiness and adaptability, the Norway Maple tends to outcompete other native maple species. Studies found that damage caused by insects and fungi was less significant for Norway maples than on their native counterparts. Durability aside, this tree has a number of weapons that it can use. One piece in its arsenal is a dense, surficial root system that inhibits undergrowth, kills off wildflowers, and monopolizes the good top soil. This prevents other species from taking roots at its base thus harming the local biodiversity. Not only will this root system wreak havoc on a natural environment but it will clash with hardscapes such as roads and pavements, cracking and altering urban landscapes with little regard. If destroying landscapes and killing wildflowers with its roots was not enough, the leaves of the norway maple are toxic both alive and in death. The living leaves are toxic to pollinators as well as other insects, once dropped and decaying the leaves of the norway maple will produce a deadly layer of detritus killing other insects and even affecting wildflower growth.. Another prong consists of the dense canopy that typically rises to 12-18 meters (40-60ft). While other trees tend to allow light through the branches and will have sparse placement of branches and leaves to facilitate this, the norway maple exerts its dominance by effectively preventing other, lower plants from gaining access to the sun. While a tall dense canopy is nothing to be alarmed over it is the “first in, last out” growth pattern that causes issues. The Norway Maple tends to get its leaves first before many other plants, and during autumn it will drop its leaves last. This means that the Norway Maple has a monopoly on canopy real estate year during the leaf bearing seasons. This denial of sustenance coupled with the Norway Maple’s other methods of dominance prevents healthy undergrowth and smaller plant life to thrive. One tree will spread thousands of seeds if not dealt with accordingly as it can quickly lead to an overgrown forest of homogenous plantlife.
Removing this pest is relatively simple for proactive towns and villages that are struggling with a local infestation, however once an infestation is established the difficulty will increase. Mature trees must be removed down to the stump and sprayed with herbicide. Seedlings are easily removed from the soil by merely reaching to the base and gently pulling it out. Controlling the spread is a little harder however there are resources for reporting sightings (Click the link here for EDD Maps to report sightings of invasive species).
After removing a cluster one can easily place suitable alternatives, and of course one must consider: Sugar Maples. While they do need deep and rich soil to thrive, it is a stand out option when trying to plant conscientiously. Once planted and settled sugar maples will be a rich addition to its environment by providing shade, housing, and food for wildlife. It comes with the added benefits of being a native species as well as part of the syrup producing family. However, if you are not sure what to add to a space to facilitate diversity, always consult your local nursery.
The norway maple is one of many invasive species that threaten local ecology. It is particularly insidious because of the ability to fully overwhelm woodlands and fields in a short space of time. To continue to ignore the problem is to invite inevitable peril to our local ecology. By highlighting species such as the Norway Maple we hope to inspire and offer solutions to townships and gardeners alike to saturate their local ecosystems with diverse species that will thrive and bring in major benefits.
Resources that you can contact for more information local to you: