As I said in my last column I have been thinking a lot about trees lately. Since losing our 85-year-old elm tree to Dutch Elm disease last summer we have been given an opportunity to plant a new one! But it does take a lot of consideration to choose the right tree for the right spot. Not all trees have the same needs and not all sites have the same characteristics. We should assess the site as to whether it has wet or dry soil, sunny or shady and wind exposure, and choose a tree that can thrive in those conditions. We must consider the mature height of the tree and we want to avoid trees that are susceptible to disease or pests, such as Dutch Elm or Emerald Ash Borer. Other characteristics to consider are shape and fall color. Knowing these traits will help you choose a tree that can perform reliably and thrive for many years.
The University of Minnesota has divided our state’s diverse ecological landscape into several regions with distinctive soils, precipitation patterns, topography and natural vegetation, and uses these to recommend trees that likely to thrive in those regions.
We live near the intersection of the Big Woods and the Anoka Sand Plain. The Big Woods has a gentle to moderately rolling typography and the soils are formed by deposits of gray, limey glacial till. Red Oak, Sugar Maple, Basswood and the American Elm were trees most often found in this biome. The Anoka Sand Plain is a flat, sandy lake plain along the Mississippi. The soils are mostly sandy and droughty, meaning it drains well and quickly.
These regional attributes are a broad, historical description of the area so it is a good idea to assess the soil in the site where you want to plant a tree. Based on the University’s recommended trees for our area there are several we are considering.
There are a few other factors we are using to determine what we will plant. We would like a fast growing species so that we may be able it see it mature close to the size of the tree we lost. We would like more fall color than our elm provided and we would want something disease and pest resistant.
There are two disease resistant elm species, Cathedral and Valley Forge. Cathedral is disease resistant to the Dutch Elm beetle and grows to about 40’x40’ with an oval shape. Valley Forge has excellent Dutch Elm disease resistance, grows to 60’x40’ with a vase like shape, and most resembles the American Elm. On the down side for us, both elm species are slow growing and their fall color is the same dull yellow of our previous tree. In addition disease resistant means just that – resistant not immune. Since we know that the disease can be spread through the root systems as well as by the beetle and we have no idea how long the disease can survive in the previous tree’s roots that are still in our yard. These trees are at the bottom of our list.
We are considering two species of oak tree, Red Oak and Bur Oak. Both are native to southeastern Minnesota. The Red Oak grows to 50+’x40+’, is pyramidal with glossy green foliage which changes to orange/red in the fall. Bur Oak is a large majestic tree, round in shape growing to 50+’x50+’. It is recommended as one of the best trees for urban sites, but unfortunately its fall color is a non-descript brown. Both species are susceptible to oak wilt disease, with the Bur Oak more resistant than the Red Oak.
Since we are looking for fall color we have been considering a variety of maples. There are many stunning maple trees in our neighbors’ yards and we were able to talk to the ‘stewards’ of these trees. This helped us to narrow the list of maple trees to consider. The first is the Sugar Maple. They are native to all of southeastern Minnesota and grow to 40’x30’ with a nice oval shape. The leaves are yellow to red in the fall and they are famously tapped for making syrup in the spring. On the down side they are very sensitive to salt and produce an abundance of seeds (helicopters) in the spring, which is something we want to avoid since the Silver Maple in our back yard already produces more than we can keep up with. The Red Maple is native to the Big Woods and Anoka Sand Plain, and also grows to 40’x30’ with an oval shape and yellow/red fall foliage. The Red Maple grows very quickly and produces a dense canopy for shade. They have the same problem with seeds except for one cultivar that has been developed to be seedless, Brandywine. A bonus is that Brandywine has deep red to red/purple foliage year-round. But it is intolerant of alkaline soils.
The Sienna Glen Maple is a naturally occurring hybrid found on an abandoned farmstead in Lake Elmo. It grows to 50’x30’ with an oval shape and bright to burnt orange fall foliage. It is an excellent performer in urban soils. The down side? Those pesky seeds. Autumn Blaze is another hybrid of a silver maple and a red maple. It is fast growing with similar attributes of the Sienna Glen, has stunning fall color, is tolerant of urban conditions and can live up to 80 years. Again the seeds can be a problem, although a seedless variety has been developed, but it can be hard to come by.
It seems we have plenty to think about before planting a tree, which may or may not happen this year.