by Jewel Pickert

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We love our trees! They provide shade, habitat for wildlife, and they take out carbon dioxide, for starters. They can also increase a home’s property value. Therefore, it makes sense to give them a little more attention.

Diversity is good for trees. In other words, if everyone planted the same tree as their neighbor’s, we wouldn’t have much diversity.

Then, if any pests specific to that variety arrived in our area, a lot of trees would be affected, like with the emerald ash borer’s devastating effect on ash trees.

More about pests later… Chris Jenkins, Parks & Recreation Director, said there are still some places in Hastings where most of the boulevard trees are ash trees.

Some pockets with older developments have less tree diversity, too.

But, for the most part, the urban forestry in Hastings is fairly diverse.

Right now, “good tree diversity management is now mandated for new developments.”

Chris said at one point, they broke up Hastings into four parts to do a tree inventory. Staff counted the boulevard trees in each of these sectors.

They counted a total of 4,500 trees. About 1,000, or 20%, were ash trees. The remainder were mixed among several varieties.

He said Hastings has a city forester now, who doubles as a Parks keeper. He has a very busy schedule.

When people ask Gary Johnson, Assistant Extension Specialist of Urban & Community Forestry, what tree they should plant, he always asks them, “What percentage of your trees are you willing to lose?”

For instance, in the Minneapolis and St. Paul areas, 90% of the street trees were American elm. When the Dutch elm disease arrived, it created an epidemic, a huge economic loss.

Gary said 17-18% of the street, park, and yard trees in Minnesota are ash trees. 20% of Minnesota’s residential trees are spruce. Maples account for more than 25% of boulevard, park, and residential trees.

Of course, ash and maple trees offer the largest spread or canopy. Plus, ash trees grow fast. Thus, they were desirable for a lot of people.

Gary said it’s not difficult to have 20 types of trees in Minnesota. He recommends not having more than 5% of trees be the same variety.

He believes Japanese lilac is being overplanted, probably because it’s resistant to the de-icing salt spray from roads.

He said the Peking tree lilac might be a better option, since “there’s no record of it becoming invasive.”

Then, there are 3-4 varieties of American elm or 3-4 varieties of Asiatic elm that are also good choices. These types would not be prone to Dutch elm disease.

You may notice that some maple leaves have black spots on them, called tar spots. This is caused by fungus, but it won’t kill the tree. Gary said, “It’s no more dangerous than us getting the sniffles.”

However, the Asian long-horned beetle is a different matter. It feasts on the leaves of many types of trees, but prefers maples.

They have already been spotted in New England and have caused havoc there.

Fortunately, they have not been seen in Minnesota…yet. Gary said it’s only a matter of time. Asian long-horned beetles have no known predator.

Oaks have a different issue. Oak wilt has been around for quite a few years. If anyone thinks they may have an oak wilt problem, they are encouraged to send a sample to the University of Minnesota Plant Disease Clinic, as the symptoms may be caused by other issues and not oak wilt.

Both the red oak group, consisting of red, black, and Northern pin oaks, and the white oak group, made up of white, burr, and bi-color oaks, can be affected by oak wilt.

If you know there is red oak wilt in your area, Gary recommends injecting the tree with a prophylactic treatment to act as a preventative before it becomes affected.

Since a red oak’s water-conducting vessels are larger, the fungus moves faster and can destroy this type of oak more quickly.

White oaks take the same kind of chemical treatment to save the tree. However, white oaks have the ability to plug up tissues when fungus is detected; therefore, they don’t normally decay.

Another oak problem is burr oak blight. It’s fairly common and specific to burr oaks. The prevalence of the blight varies yearly.

The symptoms of leaves turning brown and curling up a bit start in July.

Burr oaks can be chemically treated with the same chemical as for the other oaks. The product trade name is Alamo.

Burr oak blight is not as disastrous. A burr oak can survive many years, even with blight.

This is a sampling of a few issues with some of our favorite trees.

The next time you plant a new tree, consider investing in a variety you don’t already have. And one that isn’t overrepresented within the community.