By Joe Zeleznik, Forester

NDSU Extension

How tall will a tree grow in 23 years?

That’s a very specific question. A lot of factors go into figuring out the answer.

What tree species is it? Is it planted in a good site, with plenty of sunlight, water and nutrients? How big was the tree when it was planted? Have there been any problems, such as insects, diseases or wildlife damage? The list can go on.

As I look in my own yard, I see two 20-year-old trees, each over 30 feet tall. They’re fast-growing species and are planted in a good site. Not all trees are so impressive.

Regardless, these trees remind me of the long-term decisions we make. In September 2002, when I moved to North Dakota, a little green insect was discovered in southeast Michigan, killing all the ash trees there. The scientists studying the problem called it emerald ash borer, EAB for short.

It took quite a while, but EAB finally made its way to North Dakota back in 2024, near Edgeley. Last week, it was discovered in Fargo. 

This news isn’t surprising. We’ve been expecting it for quite a while.

Each of these finds reminds me of the challenges of managing long-lived plants such as trees. The decisions we make today can have ramifications for decades to come.

For most of the state, there’s still plenty of time to make those decisions. EAB travels very slowly on its own – about a half-mile each year. For folks in and around that find north of Edgeley, as well as those in the Fargo area, the time to make decisions is getting shorter. In the next five to 10 years, the infestation will be well established in those areas, and a lot of ash trees will be dead or dying.

What do you plan to do with your ash trees?

While doing nothing is always a management option, I don’t recommend it with ash trees around homes or in urban areas in the long run. Dead ash trees are brittle and dangerous. Removing a dead tree around a home or near power lines is awfully expensive.

Some people are already removing their ash trees and planting different species. This is a great option, as it reduces future risk and diversifies the urban forest – or even just your yard. 

Other people have decided to treat their ash trees. Several potential chemical treatments can be used to control EAB. Emamectin benzoate, in particular, is highly effective. However, it must be injected into the stem every two or three years, which can get a bit pricey.

To be clear, we don’t recommend chemical treatments unless EAB has been found within 15 miles of your location. Definitely, that covers all of the Fargo-Moorhead metro area. But most of the state is well outside that range. As mentioned above, EAB spreads slowly, so it could be a long time before it reaches your location.

Long-term injections when EAB isn’t in your area yet, could be a waste of money. If we had started injecting ash trees when I moved to North Dakota in 2002, it would have been a huge investment without a lot of return. However, if we had removed an ash tree and planted a new one, we could have a 30-foot tree by now. 

Okay, maybe a 20-foot tree is more realistic.

NDSU Agriculture Communication – Feb. 3, 2026

Source: Joe Zeleznik, 701-231-8143, joseph.zeleznik@ndsu.edu

Editor: Dominic Erickson, 701-231-5546, dominic.erickson@ndsu.edu