Black Ash

Black Ash Fraxinus nigraBlack ash (Fraxinus nigra) is much less common in the natural landscape than either white or green ash and is seldom used in landscape plantings. It is a medium sized tree (1 to 2 feet in diameter and 40 to 70 feet tall) with opposite, compound leaves with 7 to 13 leaflets. The leaflets are 3 to 5 inches long, with a toothed margin, without a stalk, dark green above and paler green below.

Habitat: Grows on moist wooded slopes and bottomlands.  Mainly found in central and northeast Iowa.

black ash leaves
Black Ash Leaves - Photo by Paul Wray, Iowa State University

Hardiness: Zones 3 though 9

Growth Rate: Moderate to Fast

Mature Shape: Slightly pyramidal, upright with a rounded crown

Height: 50 to 80 feet

Width: 50 to 70 feet

Site Requirements: Native to Iowa, ash trees grow best in full sun and moist, well-drained soils. Ash trees are tolerant of a wide range of soil conditions.

Leaves: Toothed, opposite, compound with 7 to 13 leaflets

Flowering Dates: May - June

Seed Dispersal Dates: July - October

Seed Bearing Age: 10 years

Seed Bearing Frequency: Yearly, with good seed crops occurring at one to eight year intervals with most intervening years having poor seed crops. 

Seed Stratification: Prechill seeds for 3 months at 40°F

The branches are large in diameter, stubby, and ash gray in color with prominent rusty gray to black winter buds. The winged samara fruit has a very distinct notch at the end of the wing and is broader than the other ashes. When the tree is young the bark is gray and scaly, and then becomes furrowed with age.

Black ash is native to the north east one third of Iowa; it only ranges as far west as the Des Moines River valley. Its normal habitat is on flood plains, terraces, ravines, and on wet upland pockets. Black ash prefers moist to wet soils and will, on some wetter upland sites, form almost pure stands. Black ash is a minor associate of more common species such as silver maple, cottonwood, black walnut, hackberry, elms, sugar maple, red oak, and basswood.

It is a shade intolerant species, and normally becomes established in even-aged pockets or stands following some kind of disturbance, such as logging or flooding. Black ash is considered a slow growing species; however, on better drained sites, its growth rate is much faster.

The wood of black ash is somewhat lighter, softer and weaker than green and white ashes. The wood is darker in color, and usually has more grain or figure; it is used in both interior woodworking and cabinets. It splits easily and, because of its toughness, has been used for making baskets. 

The seeds of black ash are used by game birds, songbirds and small animals.

side by side comparisons of black ash twigs, one green with bud, one gray
Black Ash Twigs - Photos by Paul Wray, Iowa State University

Diseases that Can Affect Black Ash

Insects that can Affect Black Ash

black ash fruit
Black Ash Fruit - Photo by Paul Wray, Iowa State University

black ash flowers
Black Ash Flowers - Photo by Paul Wray, Iowa State University