As summer transitions into fall, it's a good time to plant trees before winter hits. Whether planting a line of trees for a shelter belt or just a few for eye appeal in front of the house, there are some important considerations when it comes to selecting the type of trees to add to the landscape.
John Ball, a forest health specialist at South Dakota State University, recently addressed this topic at the 2018 South Dakota State Fair in Huron.
Balls says a lack of diversity in the landscape has left trees vulnerable to the threat of disease. Instead of choosing the popular ash, maple or Austrian and Scotch pine trees, he offered some safe alternatives to consider planting this fall.
"We need to discontinue planting ash due to the eventual loss (within the next 15-20 years) to emerald ash borer," Ball said.
Emerald ash borer originates from Asia and is thought to have entered the U.S. on wooden packing materials from China. The U.S. is home to 7 billion to 9 billion ash trees, according to the Arbor Day Foundation, and to date, the emerald ash borer has destroyed 40 million ash trees in Michigan alone and tens of thousands throughout the Midwest and Canada.
An infestation can result in the death of a tree in one to four years depending on its size and age. Symptoms include thinning or dying of ash tree crowns, suckers at the base of the tree, splitting bark, tunneling under the bar, D-shaped exit holes and woodpecker activity. Call the USDA emerald ash borer hotline at 1-866-322-4512 to report infestations.
With ash trees vulnerable to this damaging beetle, what is a suitable alternative? Ball has a few suggestions.
"We've over-planted maple trees here in the U.S., and because China has the largest number of maples in the world, I'm sure we'll see some pest enter the U.S. in the next 20-30 years that will wipe out our maple trees," he said. "So what's left? Consider the hybrid buckeye. It has great fall color, no nuts and is a hardy tree that is adaptable to most of South Dakota. Another great one is the hackberry. It does well in both dry and wet soils, and there aren't too many in China, so I'm not worried about disease."
Ball also listed honey locusts. "The best cultivator to plant is 'Northern Acclaim,' an introduction from North Dakota," he said.
Additionally, Kentucky coffee trees, which are native to South Dakota, would make a great choice for a windbreak or in the yard. The quaking aspen, which has striking golden yellow fall leaves and pale green bark, makes for an attractive addition in front of the house and is native to the Black Hills, so would adapt well to the area. Other options include the swamp white oak and accolade elm.
In addition to worrying about the emerald ash borer, Ball advises people to discontinue planting Austrian and Scotch pine due to increasing losses to pine wilt disease. Pine wilt is a lethal disease caused by a native nematode, and it can be prevented by sanitation and chemical injections, but it's costly, Ball says. Symptoms include rapid change in needle color or dry, brittle and discolored wood.
"You can always plant our native ponderosa pine, which can be hard to establish, or consider planting the Siberian larch, which is very cold tolerant," he said. "We also need to reduce our reliance on Colorado blue spruce due to susceptibility to diseases. Consider planting Black Hills spruce or Meyer's spruce, which has very soft needles. It's a great tree, but the deer love it, too, unfortunately, so be mindful where you plant."
Call your local Extension office before purchasing any variety of trees to ensure the preferred options are suitable for the zone area and soil type.