November 2024: White Ash

By Greg Doyle and Tyson Gregory

White Ash tree in Lexington, Greg Doyle​​

This large 45.5 inch DBH male White Ash (Fraxinus americana) is located on the

University of Kentucky campus near the parking lot behind the William T. Young Library. This deciduous tree is native to Eastern and Central North America and can grow 60 to 90 feet tall with a canopy of 40 to 80 feet. White Ash trees are best grown in full sun in rich well-drained loamy soils and are relatively drought tolerant. The pinnately compound leaves are oppositely arranged and have an average length of 8 to 10 inches. During the growing season the leaves have a prominent bicolored appearance due to the dark green upper leaf surface and the  silvery white lower leaf surface.

 Fall foliage of White Ash, Greg Doyle 

This trait is unique among other species of Ash trees in our area and is the reason why White Ash got its common name. The bark is a gray or light brown that develops deep furrowing as the tree matures. Like most other ashes (Fraxinus spp.) This tree is dioecious with separate trees producing male and female flowers that are both greenish purple in color. Flowers appear in late spring with the female flowers held in panicles of loose clusters, and the male flowers in small tight clusters. After flowering, only the female trees produce winged seeds called samaras. Masses of these pendulous samaras persist on the tree from August throughout the winter being distributed during windy or stormy conditions. In fall the leaves turn magnificent shades of orange-yellow, burgundy-red or purplish-red.

White Ash seed pod clusters, Greg Doyle

Any true ash tree (Fraxinus spp.) that is native to the Eastern United States, including White Ash, is under severe threat from an invasive insect pest called the Emerald Ash Borer (EAB). Despite their beauty these beetles are quite destructive and since its introduction to the US in 2002, the species is responsible for the death of millions of ash trees across the eastern US. Starting in June, female beetles insert eggs into the crevices and cracks of the bark on trees, then after about two weeks the eggs will hatch and the larvae begin to burrow into the bark on the tree where they will begin to feed on the cambium layer. This damage to the tree's cambium deprives the tree of nutrients and water resulting in the decline and eventual death of the tree. Adult EAB are metallic green a half inch long and an eighth of an inch wide. Interestingly the Blue Ash tend to have a better survival rate compared to White Ash and Green Ash. Currently EAB have been found in 103 of Kentucky's 120 counties, with only the far western counties unaffected so far. We do not recommend planting white or green ash trees unless you are willing to treat the tree with a systemic insecticide on a regular basis.

Dorsal view of emerald ash borer adult with elytra and wings spread. Public Domain at http://www.hungrypests.com/img/the-threat/emerald-ash-borer/small/EmeraldAshBorer6.jpg

The Kentucky Champion White Ash is located in Clark County with a height of 88 feet, circumference of 234 inches and a canopy spread of 88.5 feet. The National Champion is located in Morris, New Jersey with a height of 115 feet, a circumference of 255  and a canopy spread of 111 feet.