Black ash (Fraxinus nigra) is a deciduous tree that grows to 12 to 15 m tall. It has an attractive dark gray or brown bark and its limbs ascend upward to form a small canopy. It prefers full sun to partial shade and thrives in cold climates. It is adaptable to wet sites but is susceptible to emerald ash borer.
I. Appearance and Characteristics
Fraxinus nigra, the black ash, is a species of ash native to much of eastern Canada and the northeastern United States, from western Newfoundland west to southeastern Manitoba, and south to Illinois and northern Virginia. Formerly abundant, as of 2017 the species is threatened with near total extirpation throughout its range within the next century as a result of infestation by an invasive parasitic insect known as the emerald ash borer (Agrilus planipennis).
Black ash is a medium-sized deciduous tree reaching 15–20 metres (49–66 ft) (exceptionally 26 metres (85 ft)) tall with a trunk up to 60 cm (24 inches) diameter, or exceptionally to 160 cm (63 inches). The bark is grey, thick and corky even on young trees, becoming scaly and fissured with age. The winter buds are dark brown to blackish, with a velvety texture. The leaves are opposite, pinnately compound, with 7–13 (most often 9) leaflets; each leaf is 20–45 cm (8–18 in) long, the leaflets 7–16 cm (2+3⁄4–6+1⁄4 in) long and 2.5–5 cm (1–2 in) broad, with a finely toothed margin. The leaflets are sessile, directly attached to the rachis without a petiolule.
The flowers are produced in spring shortly before the new leaves, in loose panicles; they are inconspicuous with no petals, and are wind-pollinated. The fruit is a samara 2.5–4.5 cm (1–1+3⁄4 in) long comprising a single seed 2 cm (3⁄4 in) long with an elongated apical wing 1.5–2 cm (5⁄8–3⁄4 in) long and 6–8 mm (1⁄4–5⁄16 in) broad.
II. How to Grow and Care
Sunlight
Black ash prefers full sun and can grow in a slightly shaded environment. plant it in an open location that provides at least 6 hours of sunlight per day. If sunlight is insufficient, it will grow poorly and bloom sparsely. However, if black ash is not leafy enough, its trunk will get sunburned when the summer sunlight is strong.
Temperature
Black ash is widely distributed in temperate and subtropical regions of the northern hemisphere. It prefers cool, moist environments. It is resistant to heat, and can tolerate temperatures. Moist environments allow black ash to grow better. It can also tolerate waterlogging and drought.
Watering
It is best to water black ash daily when it has just been planted to encourage root growth. Once black ash has successfully taken root, watering once a week is enough. When the weather is dry and the tree is growing vigorously in summer, increase the frequency of watering. Before the ground freezes in late fall or winter, water once and then stop. This will provide the water it needs throughout the winter. Do not overwater the plant, as this could waterlog the soil and induce root rot.
Soil
Black ash can grow in many types of soil. It likes soil with sufficient nutrients. The soil pH is not important; it can survive in a variety of pH levels, from alkaline to acidic. Black ash prefers soil with good drainage, but can also tolerate drought and standing water.
Fertilizing
Black ash can tolerate infertile soil, but adequate nutrients promote healthy growth and reduce the possibility of pests and diseases. Apply a slow-release fertilizer (10:10:10 ratio of nitrogen, phosphorus and potassium) once every fall, and give plenty of water afterward. This will promote nutrient uptake and prevent the fertilizer from burning the roots. If your black ash is planted in spring, fertilize it in late summer; if it is planted in fall, fertilize the second spring. Because the roots of newly planted trees are weak and cannot absorb nutrients well, too much fertilizer may cause root burn.
Planting Instructions
Transplant black ash before it sprouts in the spring, so it is more likely to establish itself. First, choose a sunny, open area that provides plenty of space for it to grow. Mature black ash can grow to average heights of 12 to 18 m, so you should make sure there are no walls or other trees nearby that will prevent it from growing. Dig a hole as deep as the soil mass that encases the plant roots and twice as wide as the root mass. After planting, compact the soil and water it well.
Pruning
Prune black ash in fall so the pruning wound can heal before the plant goes dormant in winter. Pruning also prevents winter rain and snow from crushing the branches. It is best to prune young trees every year and prune mature black ash every few years. Do some pruning regularly, such as removing some dead or diseased branches. When pruning, make sure to remove branches that are overgrown or crossed over. This promotes air circulation and prevents disease. If your black ash is particularly tall, it’s best to have it pruned by a professional.
Propagation
Black ash trees can be propagated by seed or by cutting. Take cuttings in spring or summer, when the tree is less stressed. When cutting in summer, shade the tree to prevent excessive evaporation of water. Choose branches that grew in the current or last year, and cut 15 cm branches, preferably with 3-4 buds. Insert them into moist, sandy soil, and they will take root within 8 weeks.
The sowing process is complicated and black ash trees need a long time to grow, so propagating by sowing is not usually recommended. If you want to sow black ash, do it in spring, and start in a pot. Place the seeds in 1.3 cm-deep soil and cover them with plastic film. Store the pots in a refrigerator for three months. Next, place it on a heating mat (or somewhere else) and keep at 21 to 24 ℃ for three months. During this period, make sure to keep the soil moist. The seeds will germinate within six weeks.
III. Uses and Benefits
- Ornamental uses
Black ash is an ornamental tree found in many temperate gardens. It is grown for its hardiness and the beauty of its foliage and cream-colored flowers. It is resistant to pests, wind, and deer. It is a water-loving plant, and is often planted at the edges of bodies of water, or in sunny, marshy areas in the garden, sometimes as part of a rain garden.
- Other uses
Usefulness for humans
This wood is used by Native Americans of the North East for making baskets and other devices. The Shakers also made extensive use of the black ash for creating baskets. Also called basket ash, brown ash, swamp Ash, hoop ash, and water ash. It is also a popular wood for making electric guitars and basses, due to its good resonant qualities.
Usefulness to wildlife
North American native ash tree species are used by North American frogs as a critical food source, as the leaves that fall from the trees are particularly suitable for tadpoles to feed upon in ponds (both temporary and permanent), large puddles, and other water sources.
Species such as red maple, which are taking the place of ash, due to the ash borer, are much less suitable for the frogs as a food source—resulting in poor frog survival rates and small frog sizes. It is the lack of tannins in the American ash variety that makes them good for the frogs as a food source and also not resistant to the ash borer.
Varieties of ash from outside North America typically have much higher tannin levels and resist the borer. Maples and various non-native invasive trees, trees that are taking the place of American ash species in the North American ecosystem, typically have much higher leaf tannin levels.
Ash species native to North America also provide important habitat and food for various other creatures that are native to North America, such as the long-horned beetle, avian species, and mammalian species. Black ash is a food plant for the larvae of several species of Lepidoptera; see List of Lepidoptera that feed on ashes.
IV. Harvesting and Storage
If you want to collect black ash seeds for planting, harvest the fruit in the fall when it turns from green to tan. The dried seeds can be stored at room temperature for 3-5 years.
Find Where to Buy the Best Black Ash (Fraxinus nigra)
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