Categories: Gardening

13 Species of Ash Trees

13 Species of Ash Trees

Ash trees are in the Fraxinus genus within the olive (Oleaceae) family of woody plants. They are often used as shade, lawn, and street trees and were once the most planted urban tree across the U.S. You can identify ashes by looking for trees with opposite branching (not many trees do this) and compound leaves formed by clusters of leaflets. Ashes also tend to have distinctive bark that varies by species.

Ashes are dioecious trees—which means that individual trees contain either male or female parts, but not both. Male trees can be chosen if you do not want the messiness of the fruit/seeds. The fruits on ash trees are samaras, similar to the winged seeds of maples, and they are usually grouped in clusters on the stem.

Species of Ash Trees

Here are 13 species of ash trees used as shade, lawn, and street trees.

01 Black Ash (Fraxinus nigra)

The wood structure of black ash makes it a great choice for weaving, as it is pliable. This tree can grow well in cold and wet locations. Wildlife will come to visit this tree since birds and animals eat the seeds. Deer and moose also like to chew on the branches and leaves. The thick gray bark becomes fissured and scaly as the tree ages. This ash species have seven to 11 leaflets per compound leaf group, and the foliage turns yellow in the fall.

This is one of the species of ash most devastated by emerald ash borer; experts no longer recommend planting it.

Native area: Eastern Canada and the northeastern U.S.
USDA growing zones: 2 to 6
Height: 40 to 60 feet
Sun exposure: Full sun

02 Green Ash (Fraxinus pennsylvanica)

The green ash is one of the most common ashes found in the landscape and is another species that the emerald ash borer has severely impacted. It can grow in various soil conditions and is especially forgiving of conditions like pollution and salt in urban areas. Other common names include red ash, swamp ash, and water ash. The gray-brown bark forms a diamond-like pattern. The medium-green leaves include five to nine leaflets, turning variable shades of yellow in the fall. Green ash is traditionally planted as a shade or shade tree, but it is not recommended in areas where the insect is expected to arrive.

Native area: Eastern and northern North America
USDA growing zones: 3 to 9
Height: 50 to 70 feet
Sun exposure: Full sun

03 White Ash (Fraxinus Americana)

White ash is another of the more common ash trees in the U.S.—a fact that assures that it, too, has been catastrophically affected by emerald ash borer. Also known as Biltmore ash, this is the largest native ash tree, a pyramidal tree that gradually develops a fully rounded crown as the tree ages. The bark is gray in colour and develops a distinctive pattern of diamond-shaped ridges in older trees. The leaves are clusters of five to nine leaflets that are dark green on top, whitish-green on the undersides. The fall colour is a purplish yellow. This species, too, is susceptible to death from emerald ash borer.

Native area: Eastern North America
USDA growing zones: 3 to 9
Height: 50 to 80 feet
Sun exposure: Full sun

04 Blue Ash (Fraxinus quadrangulata)

The name blue ash comes from the inner bark turning blue in the air and is used to make dye. A distinctive characteristic of this species is the square shape of young shoots. In mature trees, the gray bark forms irregular plates. The leaves form clusters of seven to 11 leaflets, turning gray and dull yellow in the fall. This is regarded as one of the best ashes for dry locations, though it also does well in medium-wet sites.

Traditionally used as a shade tree or street tree, blue ash is reported to have a considerably higher survival rate in areas infested by emerald ash borer, possibly due to some inherent genetic resistance. However, it is not as resistant as some Asian species.

Native Area: Midwestern U.S.
USDA Growing Zones: 4 to 7
Height: 50 to 70 feet
Sun Exposure: Full sun

05 California Ash (Fraxinus dipetala)

The California ash, also known as two-petal ash, is a shrub or small tree that is quite different from many other ashes. The leaves have serrated edges and rounded tips, form in clusters of 3 to 9 leaflets. The white flowers have two petals and hang in fragrant clusters. This is a very good plant for drought since it has very low water needs.

Emerald ash borer has not yet affected the California ash in its native range. However, the beetle has travelled as far west as Colorado and is likely to reach the West Coast eventually.

Native area: California, Arizona, Utah, Nevada, Baja California
USDA zones: 7 to 9
Height: Up to 20 feet
Sun exposure: Full sun

06 Carolina Ash (Fraxinus Carolina)

The Carolina ash prefers wet soils and is often found in swampy areas. It is indeed native to North Carolina and South Carolina, in addition to neighbouring states. Other common names include Florida ash, swamp ash, water ash, and pop ash. This rare ash tree does well in shady conditions, and it is a very good choice for stabilizing wetland areas. The tree has the typical leaf clusters of five to seven leaflets. Emerald ash borer thus far is not present in the native range of the Carolina ash, but experts warn that its migration there is possible.

Native area: Cuba, subtropical southern U.S.
USDA growing zones: 7 to 9
Height: 30 to 40 feet
Sun exposure: Full sun to part shade

07 European Ash (Fraxinus excelsior)

As the name suggests, European ash can be found throughout Europe. It is also known as the common ash. Unlike most ashes, this tree is generally wider than it is tall when mature. Look for black buds as a characteristic to distinguish them from other ashes, which usually have brown buds. The leaves of European ash comprise seven to 13 leaflets. While some cultivars have a yellow colour in the fall, the native species drop their leaves while still green.

European ash is reportedly less attractive to emerald ash borer than are black, green, and white ashes, but it is far from immune.

Native area: Europe and southwestern Asia
USDA growing zones: 5 to 8
Height: 60 to 80 feet; sometimes taller
Sun exposure: Full sun

08 Gregg’s Ash (Fraxinus greggii)

Gregg’s ash is a large shrub that can be trained into a small tree. It can be drought-tolerant once established and can be used as a container specimen. This species has smaller leaves than other ash tree species, forming clusters of three to 11 leaflets. The bark is smooth and gray, and the branches are quite thin. Other common names include little leaf ash, Mexican ash, and dogleg ash. This is one of the few ashes that tolerate some shade. Emerald ash borer has not yet affected this tree in its native range but could do so in the future.

Native area: Arizona, New Mexico, and Texas
USDA growing zones: 7 to 10
Height: 15 to 20 feet
Sun exposure: Full sun to part shade

09 Manna Ash (Fraxinus ornus)

Manna ash is named after the flood described in the Bible because of its sweet sap extract. The sugar alcohol mannitol and the sugar mannose can be taken from this sap. This has one of the prettiest flower shows of the ashes, appearing in May; its other common name is flowering ash. The dark-gray bark on this tree remains smooth, even in old trees. The leaves form in bundles of five to nine leaflets, with finely serrated edges, turning yellow-purple in fall.

Like other ash trees that are not native to North America, this Asian species may have greater resistance to emerald ash borer, although the precise reason for this is not yet understood.

Native area: Southern Europe and southwestern Asia
USDA growing zones: 6 to 9
Height: 40 to 50 feet tall
Sun exposure: Full sun

10 Narrow Leaf Ash (Fraxinus Angustifolia)

The narrow-leaf ash is a medium- to large tree renowned for doing well in urban settings and acidic soil. Also known as desert ash and narrow-leaved ash, this tree has smooth, pale-gray bark on young trees that gradually become square-cracked and knobby as the tree grows older. The leaves are quite slender and grouped in three to 13 leaflets. The most common cultivar, ‘Raywood,’ is also known as claret ash, named for the lovely shade of purple that occurs in fall. This tree is quite similar to the related Fraxinus excelsior, but the buds are pale brown rather than black on the narrow leaf ash.

This is another non-North American ash that may have greater resistance to damage from emerald ash borers.

Native area: Southwest Asia, southern and central Europe, and northwest Africa
USDA growing zones: 5 to 8
Height: 50 to 80 feet
Sun Exposure: Full sun

11 Pumpkin Ash (Fraxinus profunda)

The name pumpkin ash comes from the fact that the base of the trunk becomes engorged and can look like a pumpkin, especially in wet soils. The other common names are swelled butt ash and red ash. This is a thick-bodied tree with a trunk covered in thick, gray, fissured bark. The leaves comprise clusters of seven to nine leaflets that turn bronze to purplish-red in fall. This tree likes moist soil, making it a traditional choice for large rain gardens. It is a very large tree that needs a lot of space. However, it is one of the ash species that has been most devastated by emerald ash borer, and experts now advise against planting it.

Native area: Eastern North America
USDA growing zones: 5 to 9
Height: 60 to 80 feet, sometimes over 100 feet
Sun exposure: Full sun

12 Velvet Ash (Fraxinus velutina)

The velvet ash is drought tolerant and does well in wet or alkaline soils, also. It is one possible choice if you need a tree that grows fast. This tree is also known as Arizona ash and Modesto ash. The gray-brown bark is rough and fissured, and the shoots emerge with a velvety coating. Emerald ash borer has recently become more of an issue for this ash, so planting is not advised in some areas.

Native area: Southwestern North America
USDA Growing zones: 7 to 10
Height: 30 to 50 feet
Sun exposure: Full sun
Continue to 13 of 13 below.

13 Manchurian Ash (Fraxinus mandschurica)

Manchurian ash is of growing interest as a landscape specimen due to its demonstrated resistance to emerald ash borer.6 Experiments are underway to cross this species with native North American ashes to develop species that can survive the beetle onslaught. It is a large tree with large compound leaves comprised of 11 leaflets that turn an attractive yellow in fall. The smooth gray bark becomes slightly fissured as the tree ages.

Native area: Eastern Asia
USDA growing zones: 3 to 6
Height: 40 to 50 feet
Sun exposure: Full sun

While many communities address the emerald ash borer issue by destroying both diseased and healthy trees to slow the spread of the beetle, some homeowners attempt to save or protect individual trees by treating them with an application of systemic insecticides containing imidacloprid, applied as soil drenches around the base of an ash tree. To be effective, the drench with insecticides needs to be repeated yearly in the spring. Treatment is most effective if it begins before the tree becomes infested. Trees that have experienced canopy loss of 50 percent or more usually cannot be saved.

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