The Roundup -

County Agent Update

 


The Elm tree is North Dakotas state tree, but lately we have noticed some of them disappearing. With the worry and finding of Dutch Elm Disease (DED) in North Dakota, there has been research done to create a resistant variety. There are no trees that are immune to DED but six varieties that are shown to be able to withstand a present of DED. The state of North Dakota, along with the surrounding states, have trained arborists on how to identify infected trees quickly and what to do to properly dispose of it. This disease actually came over from Asia, therefore the elm trees in Asia have developed some genetic resistance to it. When this disease came over to the United States, it wiped out large populations because our trees had never been exposed. The University of Wisconsin and the Morton Arboretum in Chicago have incorporated the resistant genes of the Asian elms to theAmerican elms, they have released one of the six varieties that will be listed below.

It is believed that less than 1 out of every 100,000 American elms are genetically resistant to DED, those are quite small odds. The elm trees in your yard, and also the six I will list below, keep them growing vigorously. Keeping them well watered, adding fertilizer when needed and training young trees, by cutting the weak narrow branches will help them grow the strongest and healthiest they could be. The varieties listed below all have dark green foliage, grow fast and have an arching vase-like habit.

- American elm (Ulmus americana)

• ‘Jefferson’ Very Tall (65’ H x 50’W) Zone 4, sterile seeds

• Prairie Expedition- North Dakota variety, well suited for prairies, Large (55’HW) Zone 2 hardiness

• St. Croix- Metro Minnesota, Mammoth size (60-75’ H x 70-90’W)

- Japanese Elm (Ulmus japonica)

• ‘Discovery’ Manitoba, sturdy, small. (35-40’ HW) Slower growth (compared to others) Drought tolerant. Resists leaf beetles

- Japanese elm hybrids (Ulmus japonica complex)

• ‘Cathedral’ Wisconsin origin, very fast growing, must prune, drought tolerate (50’ HW)

• Triumph- Chicago origin, zone 4, very fast growing, sturdy, urban tolerance, (60’ x 40’ W)

This information was from the North Dakota State University Yard and Garden Report.

 

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