A beautiful, upright, rounded form. Great fall color. Hardy and adaptable. A native tree in many parts of the U.S. The ash tree certainly has its desirable attributes, which is why many people love it.
But just like any healthy urban forest, your home landscape needs variety. To ensure your landscape trees survive specific pests and diseases, you never want too much of one type of tree.
Think you have an ash tree in your yard or looking to add one? Let’s look at how you can identify one of these trees and how you can take care of it and keep it protected from pests, particularly the Emerald Ash Borer.
As a relative of the olive tree, there are 65 species of ash trees across the world, with 17-18 species native to the U.S.
These medium to large deciduous trees grow in parks, forests, and residential neighborhoods. Most ash tree varieties grow to heights between 50 and 80 feet with spreads of 50 feet in USDA winter hardiness zones 2 to 9.
Some species of ash trees can grow along streams or in wetlands, while other species grow in uplands and are drought tolerant.
What does an ash tree look like? Ash trees have dark green leaves in spring and summer.
Almost all ash species have compound leaves which grow in groups of five, seven, or nine leaflets on an opposite branching structure, which is actually pretty unique. If you have a tree with opposite branching and compound leaves, it may very likely be ash. Ash trees produce small clusters of small white or purple flowers after the leaves emerge, and female trees bring forth light brown, winged seeds that resemble paddles and drop in late fall or early winter.
In fall, ash tree foliage can turn golden yellow or reddish-purple, depending on the species.
With dense hardwood, ash tree wood has made a great choice for furniture and wood flooring. Ashwood has even been used to make baseball bats, guitars, and tool handles.
The bark that covers this wood is also interesting. Older ash trees have grayish bark with pointy ridges in a woven diamond pattern.
Of the ash species native to the U.S., these 5 may be found in your neighborhood.
The ash tree’s biggest threat is the Emerald Ash Borer, an invasive beetle decimating ash trees in North America since 2002. As of 2019, the Emerald Ash Borer has killed untold millions of ash trees. Green, white, and black ash all have been killed in very high numbers. Emerald ash borer has not yet been detected in the southwest U.S, but it also killed Arizona ash when it was planted as a shade tree in China.
Adult Emerald Ash Borers are bright green in color. They lay their eggs in bark crevices. Once the eggs hatch, the larvae bore into the tree’s cambium layer and eat through its vascular system. This stops the tree’s ability to move water and nutrients.
Initially, when identifying a tree infested by Emerald Ash Borer, you may notice some canopy thinning and perhaps branch die-back. You may also notice that woodpeckers seek out Emerald Ash Borer-infested ash trees and feed on the larvae. Emerald Ash Borer infestations symptoms include D-shaped exit holes in the tree’s bark. This is a result of adult beetles leaving the tree, which typically happens in May, June, and July. Splitting bark and S-shaped galleries or tunnels under the bark can also be signs of Emerald Ash Borer infestation.
Managing Emerald Ash Borer requires repeated insecticide treatments with different options depending on the situation. Bark treatments are repeated two times per year, soil treatments are repeated every year, and stem injection treatments are repeated once every two years. . A tree that has experienced less than 30% decline can be saved, but those with canopy decline beyond that have less of a chance for recovery. Prevention and early detection are your best methods for control, as treatments are most effective if they begin before or very soon after a tree is infested. If you suspect your ash tree is threatened by an attack from Emerald Ash Borer, contact your local arborist for an ash tree inspection, as well as some prevention and treatment tips and strategies.