Another post in our series on native alternatives to invasive plants.
In 2005, after moving into our current house, we purchased a variety of bareroot native shrubs from the DNR to naturalize in the yard. These shrubs included Nannyberry Viburnum, High Bush Cranberry Viburnum, American Hazelnut and Red Osier Dogwood. With two years of drought they were very slow to establish until the following years when we had adequate rainfall. I noticed that some of the High Bush Cranberry were growing substantially more than others in the same area and were already flowering.
In the winter of 2008, as my High Bush Cranberry Viburnums (HBCV) had really taken off that previous summer, I was reading the book Invasive Plants of the Upper Midwest by the late Elizabeth Czarapata. In her book she describes how the European HBCV is invasive and is so similar in appearance to the native American HBCV that it’s often mistaken for the native.
The main difference between the American and European High Bush Cranberry Viburnum is the gland shape on the leaf petiole.
I anxiously waited for spring and for my HBCV to leaf out so I could investigate these glands. On the European HBCV, the glands are larger, more numerous and concave or ear shaped. On the American HBCV, the glands are smaller, narrower and rounded on the top. It turns out that 70% of my HBCV were in fact European.
Other differences include:
- Growth Rate (European has a higher growth rate),
- and Leaf Shape.
The European HBCV “leaf lobes are shorter and less pointed, and its fruit are bitter, causing birds to avoid them.” (Invasive Plants of the Upper Midwest, Czarapata, Elizabeth). The fruit on the European HBCV persist longer into the winter as the birds avoid them until there isn’t anything else available.
The birds do feed on the fruit however, as this is believed to be the primary way it has naturalized in wetland edges, riparian areas, and other lowland moist sites in southern Minnesota. It is also prevalent in states eastwards to Maine including Ohio and Pennsylvania. “It [European HBCV] seems to compete more aggressively than the native high bush cranberry and is better able to withstand habitat disturbances. In the area around the Twin Cities and southward, the European species is now more common than the native species.” (Trees and Shrubs of Minnesota, Smith, Welby R.)
After speaking with natural resources professionals, I learned that local native nurseries as well as the DNR were unknowingly propagating the European HBCV from softwood cuttings of wild stock and their own stock which they believed was the American HBCV. They have since checked all of their stock and now only sell the native HBCV.
European HBCV is widely sold at local nurseries. Check the native ones too as they could be unknowingly propagated from the European HBCV.
Here’s some common cultivars sold at nurseries:
European High Bush Cranberry Viburnum
Compact European Cranberry – Viburnum opulus ‘Compactum’
Dwarf European Cranberry Bush – Viburnum opulus ‘Nanum’
American High Bush Cranberry Viburnum
Bailey Compact – Viburnum trilobum ‘Bailey Compact’
Hahs American Cranberry – Viburnum trilobum ‘Hahs’
Redwing Highbush Cranberry – Viburnum trilobum ‘JN Select’
Wentworth Highbush Cranberry – Viburnum trilobum ‘Wentworth’
For more photos of the European High Bush Cranberry, visit the Invasive.org website.
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