It is a slender tree—one of the slenderest trees found in North American forests—with a narrow trunk that rarely reaches more than two feet in diameter. Black ash is often leaning or bent. The grey, fissured bark becomes scaly as the tree ages. It’s a long-lived tree that can get 150 and in some cases up to 250 years old. Black ash has male and female trees, and it produces small winged seeds in hanging clusters called samara that ripen in September and can remain on the tree until the late fall. Game birds and songbirds such as wood ducks, wild turkeys, and cardinals, as well as mammals, including black bears, foxes, and squirrels, feed on the seeds. Beavers like to eat the bark and wood. Bats use it as maternity roosts where they have their babies. Black ash trees also serve as shelters for tree frogs, wood frogs, and spring peepers. And, not a wildlife value appreciated by home gardeners: Deer like to munch on the young branches. When most elm trees were wiped out in North America in the last century, ash trees were widely planted in forests to replace them. Since 2002, however, ash trees have their own deadly threat, the emerald ash borer, a pest originating from Asia that has killed hundreds of millions of ash trees in North America. Black ash is a moderate to fast grower and the wood is not as dense and strong as white ash. This makes it more vulnerable to be blown over or damaged in a strong storm, which is a factor to take into consideration when selecting a location.
Light
Black ash needs full sun. While a young tree might be all right in partial shade, the older the tree gets, the less it will tolerate shade.
Soil
The tree naturally grows in moist to wet locations, so it does well in any deep soil that contains loam, sandy loam, a clay loam combination, or moisture-retaining peat. It is tolerant of acidic soil.
Water
Black ash does not tolerate drought. It needs a location with ample moisture but not standing water. A location near a stream or creek where the water is moving and aerated is ideal. The tree can even be planted in a location that is flooded for the duration of up to two months during the growing season.
Temperature and Humidity
Black ash is a very hardy tree but due to the nature of its wood it is highly susceptible to ice damage. Humidity does not have any known adverse affects.
Fertilizer
If the soil isn’t naturally rich and fertile, amend it with a generous amount of organic matter.
Varieties of Black Ash
Fraxinus nigra ‘Fallgold’ is a narrow, upright cultivar that grows only to about 30 feet tall. Its small size, neat appearance—it is a male seedless tree—and attractive deep yellow fall foliage makes it a good choice for home gardeners. This cultivar is even hardier than the species and can be planted in zone 2b.
Common Pests/Diseases
Common diseases of ash trees are ash yellows, verticillium wilt, and ash anthracnose. The most serious threat however is the emerald ash borer (Agrilus planipennis), common acronym: EAB. This beetle from Asia was discovered in Michigan in 2002. It’s the larvae that cause irreparable damage; they feed on the inner bark, so the transport of water and nutrients is disrupted and the tree dies. Emerald ash borer has already killed hundreds of millions of ash trees in North America. It is currently found in 35 US states of the US, and in the Canadian provinces of Ontario, Quebec, New Brunswick, Nova Scotia, and Manitoba. The Black Ash is extremely prone to EAB, so unless you are ready to care for this tree with regularly preventative injections by a certified arborist to keep this pest at bay, you might want to pick a different tree for your landscape.
