Black Ash is a long-lived medium size native deciduous tree growing 30 to 50 feet in height with a narrow rounded crown of upright branches which are usually restricted to the upper part of the trunk on mature trees.
The bark is gray, smooth and often warty on young trees, then becoming corky and fissured into soft scaly plates that rub off.
Twigs are gray and stout, hairless. Leaf scars are nearly circular and the lateral buds appear at the top of the scar. These buds are almost black in color as are the terminal buds which are short and conical.
Leaves are opposite and pinnately compound, 12 to 16 inches long, with 7 to 11 dark green leaflets that are broadly lance-shaped in form, whose margins are saw-toothed. Each leaflet is stalkless, except the terminal leaflet, and the entire leaf itself has a short stalk. The underside of the leaflet is paler with tufts of brown hair along the leaf vein. Fall color is yellow to brown.
Flowers: The tree is dioecious, that is the male and female flowers are on different plants. (although a few trees may be monoecious (both flowers on the same tree). Both appear before the leaves in small dense clusters. They are purplish, only 1/8 inch long, without a calyx or corolla. Male flowers have two stamens with short anthers and the flowers turn darker after release of pollen. The female flowers have a pistil and an extremely short calyx. Both flowers occur in tight panicles at the leaf scar axils of the prior year's wood. The clusters expand during development, the female clusters much more than the male. Flowers are cross pollinated by wind. Some studies indicate that male trees flower every year but female trees flower every 2 to 5 years.
Seed: Female flowers mature to a single broad winged samara, 1 to 1-1/2 inches long, that is flattened in appearance due to the thin seed cavity for the 1 to 3 small seeds (usually one), and the wing extends to the base of the samara. The tip of the wing is rounded and sometimes with a slight notch. See comparison photo below. These turn straw-yellow, mature in autumn and disperse by wind in fall and winter. They do not germinate for several years as a cold stratification period and scarification is needed. Trees usually need to reach 30 years of age before they bear significant seed.
Habitat: Black Ash prefers moist soils with full to partial sun. A variety of soils is tolerated as is excessive moisture, unlike Green Ash. Also unlike Green Ash, seedlings do best in full sun. The root system is shallow and spreading. It can re-sprout from stumps and cuts.
Names: The genus, Fraxinus, is the old Latin name for this genus meaning 'spear'. Ash wood, being tough and elastic, was originally used for spears and bows in the old world. The species, nigra means 'black' which is the color of the buds. The author name for the plant classification - ‘Marshall’ refers to Humphry Marshall (1722-1801), American Botanist, who published in 1785 - Arboretum Americanum: The American Grove, an Alphabetical Catalogue of Forest Trees and Shrubs, Natives of the American United States.
Comparisons: Black Ash can be confused with Green Ash (F. pennsylvanica) and White Ash (F. americana). Comparison of the samaras is the best method of identification however Black Ash can also be identified by the smoother bark and the leaflets without stalks. In its native environment it is found in marshes and wet places.
Above: 1st photo - The crown is irregular and branches are often only on the upper part. 2nd photo - On young trunks the bark is gray, smooth and often warty. 3rd photo - Bark on a old tree, 18 inches in diameter.
Below: 1st photo - Leaves are pinnately compound, with 7 to 11 dark green leaflets whose margins are saw-toothed. Lateral leaflets are sessile. 2nd photo - New growth showing the large attachment point of the leaf which makes the almost circular leaf scars.
Below: 1st photo - Lateral buds are almost black in color as are the terminal buds which are short and conical. 2nd photo - An individual leaflet, upper side and (3rd photo) the paler color of the underside with the characteristic tufts of brown hair along the leaf vein.
Below: 1st & 2nd photos - Female flowers developing. 3rd photo - Male flower cluster
Below: 1st photo - Developed stamens of the male flowers. 2nd photo - Samara in the yellow autumn stage. Note the full wing with rounded, slightly notched tip.
Ash samaras are a key distinguishing characteristic of the three common species. Position of the wing vs the seed and thickness of the seed are important. Overall length and width are variable between trees within a species and not useful.
F. nigra has a flatten broad seed with the wing extending to the base of the seed cavity. F. americana has a noticeably thick seed, rounded, and the wing does not extend beyond the seed cavity. F. pennsylvanica has a smaller seed with the wing extending into the seed cavity, but not all the way to the base.
Notes: Black Ash was present in the Garden at the time of Martha Crone's 1951 Garden Census. Although not noted in Eloise Butler's log for the early years of the Garden, it is probably indigenous. In North America it is found in the NE quadrant, from Manitoba in Canada eastward except for Labrador and in the U.S. from North Dakota, Minnesota and Iowa eastward to the coast and south as far as Kentucky and Virginia. Within Minnesota it is generally found east and north of a diagonal line drawn from Fillmore county to Clay county - generally absent in the SW and the NW. This is the northern most native ash in North America. Only three species of ash are native to Minnesota and with known populations - Black Ash plus White Ash (F. americana) and Green Ash (F. pennsylvanica).
Uses: Black Ash wood is somewhat heavy but not strong. It can be used for furniture, cabinets and other small uses not exposed to moisture. As the wood splits easily it has been used in basket making. This use developed because it is the only tree in North America where the growth rings (spring and summer) are not connected by fibers, allowing the sturdy summer wood to be peeled away in strips after the weak spring wood is crushed with a mallet.
References: Plant characteristics are generally from sources 1A, 32, W2, W3, W7 & W8 plus others as specifically applied. Distribution principally from W1, W2 and 28C. Planting history generally from 1, 4 & 4a. Other sources by specific reference. See Reference List for details.
Friends of the Wild Flower Garden, Inc. Text and photos are by G. D. Bebeau unless otherwise credited. "www.friendsofthewildflowergarden.org"