ISSUE 11 July 19, 2007
IMPROVED WOODY PLANTS FOR NORTH DAKOTA
Over the years, NDSU horticulturists have released improved woody plants that perform well in North Dakota. I asked Dr. Dale Herman (NDSU horticulturist, woody species) for information on a few noteworthy woody plants, and he graciously provided me with descriptions of many varieties for North Dakota. Below is an extremely brief, partial list of some of these releases and a few notes on their characteristics.
BIRCH TREES WITH IMPROVED RESISTANCE TO BRONZE BIRCH BORER
Prairie Dreams® Paper Birch (Betula papyrifera ‘Varen’, PP15,768) - Originating from a seed source in Killdeer Mountain in western North Dakota, this selection can be grown singly or as a multitrunked specimen. It is resistant to bronze birch borer attack, based on at least 30 years of evaluation where insect pressure was high. It has a semi-pyramidal to upright-oval growth habit, becoming more broadly oval with age. It is reportedly very well adapted to our region, and its resistance to the bronze birch borer make it highly desirable here. USDA hardiness zone 2b-3.
Prairie Vision® Paper Birch (Betula papyrifera ‘VerDale’, PP15,944) - Like other paper birch, this selection from Asian white birch native to western China has white bark with blackish markings. This specimen has performed well in our region and has also resisted attack by the bronze birch borer for at least 30 years in evaluation. USDA hardiness zone 3.
Northern Tribute™River Birch (Betula nigra ‘Dickinson’) - River birch usually have darker bark than paper birch, and the river birch reportedly have high tolerance or resistance to attack by the bronze birch borer. This cultivar originated from a tree growing in Dickinson, ND, and it does not seem prone to iron chlorosis as other river birch may be. Ivory colored bark with contrasting coppery-bronze exfoliating bark certainly adds interest to a landscape. As the tree ages, the exfoliating bark becomes more uniformly tannish-brown. This cultivar is currently under propogation and testing by commercial nurseries.
ELM TREES WITH DUTCH ELM DISEASE RESISTANCE
Prairie Expedition® American Elm (Ulmus americana ‘Lewis & Clark’) - This selection is a lone survivor among American elm trees that died from Dutch elm disease along the Wild Rice River southwest of Fargo. In evaluations where this tree was inoculated with the fungus that causes Dutch elm disease, it showed high resistance. This selection produces the classic umbrella form so typical of American elm. USDA hardiness zone 2b-3. Available from nurseries in near future.
The following web links provide more information on woody species that perform well in our region:
NDSU Plant Diagnostic Lab