Master Gardener Sue Morris: Suggestions for replacing ash trees
Suggested ash tree replacements if looking for diversity in your landscape.
Here are some trees you might want to consider if you are looking for diversity in your landscape.
Last week in this column I gave some dire predictions for ash, maples and Colorado blue spruce, which were highlighted in a talk by SDSU Extension professor John Ball.
He predicted that within the next 15 to 20 years, we will have no ash trees so it is a good idea to start planting some alternate trees.
The hackberry is a good replacement for ash. The height gets to be 40 to 60 feet with a spread of 30 to 40 feet. It has a rounded shape with yellow fall color. It is hardy to zone 3 — we are zone 4 in west central Minnesota — and is well-adapted to the entire region and native to most of it. It tolerates alkaline and droughty soils and he calls it the “new” ash tree.
I have several on my farm and I much prefer them to ash. (In fact I’m an ash "hater" — as they are always dropping branches and are generally messy trees.) Here I find hackberry to grow slower than ash.
Back in 1981 we planted an additional windbreak on the northeast side of our building site. After the first two rows of Black Hills spruce, it was alternate rows of ash and hackberry as suggested by Soil and Water Conservation agency. The hackberry were much slower growing but are now 100% better trees than the scrappy looking ash.
Hybrid buckeyes are another suggestion by Dr. Ball. Height is 25 to 30 feet with a spread of 25 to 30 feet and an oval shape. Fall foliage color is brilliant oranges and reds. They are hardy and adaptable to our region. He suggested Autumn Splendor variety. It has lime-green flowers in late spring with limited fruit production.
I have had experience with horse chestnut trees. There was one in front of our house for probably 75 to 100 years. It was way higher than two stories, but a few years ago we had to have it removed as it was becoming hollow and a threat to the house in a windstorm.
I always called that my “best friend” as it was such a wonderful shade tree — even though I had tons of horse chestnuts to clean up every fall and a lot of compound leaves as well.
I still have offspring from that tree as squirrels planted them in other parts of the yard and the woods, not to mention the flower beds.
When the chestnut bloomed in the spring, it was alive with bees and orioles so it was fun bird watching out the kitchen window.
Another tree he mentions is the Kentucky coffeetree that gets to a height of 40 to 60 feet with a spread of 40 to 60 feet. Rounded shape. Flowers are small but interesting and has yellowing fall color. Best on moist, well-drained soils and will tolerate a pH of at least 7.5.
True North is a male cultivar. I have several of these and have no idea the cultivar as they were dug from a friend’s woods. They are about 30 years old and have never produced a flower or seed pods. They have compound leaves.
Black walnut is another suggestion. I have them in two areas — two rows on the north side of buildings and two rows on the south side of the buildings. They are slow growing and in a place where the nuts don’t have to be raked up.
The squirrels take care of a lot of them. If you have enough patience and strength, the nuts are great for baking.
The roots produce juglone, which has been said to inhibit the growth of garden produce. I had them north of my vegetable garden and didn’t have a problem and the raspberry bed was near them and I still have an apple tree growing under the partial shade of one.
In case readers would like to try growing some from seed, let me know and I’d be happy to share. I’m sure the squirrels wouldn’t mind.