Tree Talk: Return of the Elms

American elm is North Dakota's state tree. Elms were a natural choice for planting in communities and windbreaks because it is one of our tough native species. It is these tree canopies that, with their beautiful vase-shape, form leafy "tunnels" along elm-lined streets.

Then, the unthinkable happened: Dutch elm disease (DED) entered the U.S. in the 1920's and found its way to Mandan in 1969. It was first identified in the Netherlands, hence the name.

From there, it spread quickly to other countries, including the U.S. DED has spread to every county of the state, decimating American elms in North Dakota's communities, windbreaks and native forested stands. Dutch elm disease is caused by a fungus which infects the vascular system, stopping the flow of water from the roots. The disease is transmitted by small bark beetles from infected trees to healthy trees (the fungal spores attach to the beetles), or it can pass from a diseased tree to a neighboring elm tree through root grafts. It is also spread by movement of firewood from infected trees. Don't move firewood from "sick" trees! The first signs of DED are "flagging" branches, where leaves wilt, turn yellow and then brown, and finally fall to the ground due to lack of water. Prompt removal and disposal of infected trees (including infected firewood!) is key to managing DED in any community. The cities of Fargo, Grand Forks and Bismarck still offer the "elm tunnels" along streets in old neighborhoods, possible because of the aggressive management of DED in these communities. For high-value trees, repeated fungicide injections can protect large trees from becoming infected.

So – is this the end of American elms in small towns? No! There are DED-resistant elms widely available in the nursery trade. Diversity is key to a sustainable "community forest" and elms are being replanted in many communities, including New Rockford. 'Prairie Expedition' is an NDSU release, propagated from a 'lone survivor' native elm discovered along the Wild Rice River in the southeastern corner of the state. This selection shows great resistance to DED and is a wonderful option for increasing the elm populations in North Dakota communities. Other elms that work well in North Dakota include 'Princeton' and 'Valley Forge'. Hybrid elms include 'Cathedral', 'New Horizon', and 'Pioneer'. Japanese elms to try include 'Discovery' and 'Northern Empress,' one from NDSU that produces a beautiful fall burgundy red canopy.

Take a Look: See 'Prairie Expedition' American elm trees planted on the 1100 block of 3rd Avenue North. One of the most majestic mature elms in New Rockford is on the corner of 2nd Street South and 2nd Avenue South, where it graces the entire front yard of this home. Shade is a precious commodity on a hot day.

REMINDER: WATER your trees weekly, both young and old, with a slow trickle from a hose. Mulch any newly planted trees to retain soil moisture, suppress weed growth, and to keep mowers and trimmers away from tender bark on young trunks.