by Nick Perry
When you see or hear the word autumn, what is the first image you have? Many people immediately think of the spectacular color changes in the foliage. The magnificent reds, yellows and oranges can really be prominent during sunny autumn days.
This week’s “Tree of the Week” does not disappoint when it comes to displaying brilliant fall coloring.
The Highland Park Maple, Acer grandidentatum x saccharum ‘Hipzam’, is part of the Sugar Maple family and is native to North America. It is classified as a Zone 4 tree on the USDA hardiness map and can be grown in the majority of Minnesota.
The Highland Park Maple is not a very large tree in size. It can grow between 30 and 50 feet in height and its spread can vary from 20 to 25 feet. With a pyramidal growth habit, it can be used in both group plantings or as a stand-alone accent tree in a residential yard. It requires full sunlight and grows at a medium rate. Because it can handle adverse growing conditions, this maple may be able to grow where other similar maples do not fare as well. The capability to tolerate dry soils and urban pollution allows it to grow in commercial and residential environments. The ability to resist pests and diseases also add to its allure. It shouldn’t be considered for boulevard plantings, as it does not fare well in saline soils and its lateral branches typically arise roughly 78 feet off the ground.
The tree does not produce any showy flowers or fruit. It does, however, have very nice foliage. The leaves are sturdy and tatterproof. In the spring and summer, they are a rich dark green. In the fall, they begin to change color producing gorgeous reds, yellows and oranges.
Young, red branches also add an attractive element to the landscape throughout the year. The red branches can really look picturesque against the freshly fallen snow.
The University of Minnesota has successfully grown the Highland Park Maple species at their St. Paul field location. They will provide several of these specimens to local areas including the City of St. Paul and the Minneapolis Park and Recreation Board.
Photo Courtesy of Willoway Nurseries, Inc.
Willoway Nurseries Inc. Acer grandidentatum ‘Hipazam’ – Highland Park Maple. 2015. Willoway Nurseries inc. Avon, OH. Willoway Marketing. Web. 23 October, 2015.
Plant Finder: Highland Park Bigtooth Maple. (n.d.). Chalet Nursery website. Retrieved from
The Tree Farm: Highland Park Bigtooth Maple. (2010). The Tree Farm website. Retrieved from
Acer grandidentata. ‘Highland Park’ Bigtooth Maple. (n.d.). Robinson Nursery website. Retrieved from http://www.robinsonnursery.com/wpcontent/uploads/2012/02/Acergrand.HighlandPark.pdf
As Tough As Nails. (2010). Lake County Nursery website. Retrieved from
by Daniell Ringle
The story of planting American elm trees has become much more complicated since Dutch elm disease (DED) arrived in Minnesota. Prior to the arrival of the disease, elm saplings were often dug up from the wild and transplanted into cities and communities. Now we have to go through a rigorous process to find disease resistant elm cultivars, because anything we plant from the wild has a high likelihood of becoming infected with DED. There are some disease-tolerant elm cultivars being planted in Minnesota, but they are not from the state (Ed. As of this writing, the St. Croix™ Ameican elm did not have wide commercial availability. St. Croix™ is the first disease-resistant American elm selected from a Minnesota-native parent tree. It is currently being produced and marketed by Bailey Nurseries and is now available in retail and wholesale nursery and garden center outlets.) Team Tree is trying to find resistant elm trees in each quadrant of the state so that we can have Minnesota grown cultivars adapted to our unique climate. We are specifically looking for mature elms that have lived since DED was found in Minneapolis in the 1960’s and likely have natural resistance to the disease. After identifying a specific mature elm that we would like to replicate, we collect fast growing branch tissue during the winter dormancy period.
Collecting elm cuttings in Mankato, MN
Branch material for experimentation
When we are ready to use the dormant branch material, last year’s new growth is grafted or processed as stem cuttings to make a clone genetically identical to the tree it came from. To make a rooted cutting, we cut a section of branch material several inches in length and plant it in a rooting medium. To encourage root establishment, we dip the cutting in a concentrated hormone solution that originates from a growth regulator that plants produce to initiate the growth of new roots.
Rooting cuttings (of cottonwood, not elm)
Modified cleft grafting, however, is best cloning technique if we want quick growth, because the tree can allocate all its energy into one small grafted branch, instead of having to focus on developing new roots. When grafting, a wild elm seedling (rootstock) is used for the base of the new tree and a few inches of potentially resistant branch material (scion) is grafted to it. We do not allow the rootstock material to form leaves and branches, so the resulting tree will be completely from the scion wood. The purpose of the rootstock, as you could likely guess from its name, is solely to be the root system of the tree.
Grafted elm clone
Successfully leafed out elm in its first season post-graft
Mature, disease resistant elm
Because we usually graft in the wintertime, we keep the newly grafted trees in a greenhouse so they have a head start on the growing season. We then move them out to our nursery for the summer. From this time until the tree reaches 3 to 5 years of age, the main focus is on growing a large healthy clone. Once the tree is large enough, it is inoculated with Dutch elm disease to test for resistance. Any trees that have shown that they can survive exposure to DED after several rounds of testing will be used for restoring American, red and rock elm to Minnesota’s landscape. We hope that someday the fruits of our labor will pay off and result in a specimen such as the one posted above.
Team Tree in SW Minnesota
Team Tree in Lake City, MN
by Chad Giblin
One hundred years ago, well before Dutch elm disease (DED) made its way to our shores, we had the time to ponder the many wonderful qualities of America’s favorite shade tree, the American elm (Ulmus americana). In April 1908, C.C. Laney published this wonderful article in The Garden Magazine:
One might dismiss this article as just a bit of horticultural antiquity, but there is much to be learned from it. These elm forms can still be found on the streets and in the parks throughout America. Look around and you’ll likely see a “willow-type” or “pitcher-type” elm. In the Twin Cities area we’re apparently quite lucky to have many of the reportedly “rare oak-type” American elms.
Take a few moments out of your busy day and travel back in time when we could encourage our children to:“know [these elms] by name … to make pilgrimages to them, to hold picnics and little parties under them. And so a love for the trees would be cultivated by association and the next generation, being friends to the trees, there would be no need of enacting laws to compel their preservation.” – C.C. Laney, 1908
We all had a great time at Shade Tree Short Course this year. Here are a couple of presentations done by University of Minnesota Forest Resources staff and students at the STSC.