Green ash is an adaptable native tree planted in both conservation and home settings. It makes an attractive, fast-growing shade tree. If you want to know how to grow green ash, read on. You’ll also find other green ash information as well as tips on good green ash tree care.
I. Appearance and Characteristics
Fraxinus pennsylvanica, the green ash or red ash, is a species of ash native to eastern and central North America, from Nova Scotia west to southeastern Alberta and eastern Colorado, south to northern Florida, and southwest to Oklahoma and eastern Texas. It has spread and become naturalized in much of the western United States and also in Europe from Spain to Russia.
Other names more rarely used include downy ash, swamp ash, and water ash.
Fraxinus pennsylvanica is a medium-sized deciduous tree reaching 12–25 metres (39–82 feet) (rarely to 45 m or 148 ft) tall with a trunk up to 60 centimetres (24 inches) in diameter. The bark is smooth and gray on young trees, becoming thick and fissured with age. The winter buds are reddish-brown, with a velvety texture. The leaves are 15–30 cm (6–12 in) long, oppositely arranged, pinnately compound with seven to nine (occasionally five or eleven) leaflets, these 5–15 cm (2–6 in) (rarely 18 cm or 7 in) long and 1.2–9 cm (1⁄2–3+9⁄16 in) broad, with serrated margins and short but distinct, downy petiolules a few millimeters long. They are green both above and below.
The autumn color is golden-yellow and depending on the climate, green ash’s leaves may begin changing color the first week of September. The flowers are produced in spring at the same time as the new leaves, in compact panicles; they are inconspicuous with no petals, and are wind-pollinated. The fruit is a samara 2.5–7.5 cm (1–3 in) long comprising a single seed 1.5–3 cm (5⁄8–1+1⁄8 in) long with an elongated apical wing 2–4 cm (3⁄4–1+1⁄2 in) long and 3–7 mm (1⁄8–9⁄32 in) broad.
It is sometimes divided into two varieties, Fraxinus pennsylvanica var. pennsylvanica (red ash) and Fraxinus pennsylvanica var. lanceolata (Borkh.) Sarg. (syn. var. subintegerrima (Vahl) Fern.; green ash) on the basis of the hairless leaves with narrower leaflets of the latter, but the two intergrade completely, and the distinction is no longer upheld by most botanists.
Like other species in the section Melioides, Fraxinus pennsylvanica is dioecious, with male and female flowers produced on separate individuals.
Seedlings of the tree have a high tolerance to water logging which may explain why the natural habitat of green ash is almost exclusively stream sides and bottomlands. The large seed crops provide food to many kinds of wildlife.
II. How to Grow and Care
Sunlight
Green 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 green ash is not leafy enough, its trunk will get sunburned when the summer sunlight is strong.
Temperature and Humidity
Green Ash, with its dark green leaves, is planted throughout the United States. Hence, Green Ash can tolerate different temperatures. Therefore, it is not only a drought-tolerant but also a cold-hardy species that can grow in USDA hardiness zones three to nine.
At first, you may need to protect ash seedlings from too-wet soil and high winds, providing them with a stake.
Watering
It is best to water green ash daily when it has just been planted to encourage root growth. Once green 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
Green 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. Green ash prefers soil with good drainage, but can also tolerate drought and standing water.
Fertilizing
Green 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 green 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 green 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 green 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 green 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 green 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 green ash is particularly tall, it’s best to have it pruned by a professional.
Propagation
Propagating your green ash is quickly done through cuttings but is not recommended, as the emerald ash borer is a problem. So, the best thing to do is to grow your Green Ash from seeds. But it is a time-consuming process and also a difficult task.
The reason is that the seeds need a repeated round of cold stratification for a long time, up to a year. The problem is that not all seeds are fertile and will take several attempts to sprout into seedlings.
If you have dried seeds, it helps to plant them a half inch deep into a pot with moist soil and then seal them in a plastic bag to chill for about three months. Then, you need to place the container warmly for another three months.
Next, chill it for up to three months in a plastic bag and repeat until you see the seeds sprouting.
Pests and Diseases
Borer Infestation
Monitor for signs of borers such as ash borer, lilac borer, and carpenter worm. Treat young trees by drenching the trunk with insecticide in spring. For more giant trees, seek professional assistance for trunk injection with insecticide.
Emerald Ash Borer
Watch for signs of infestation, including dieback and D-shaped exit holes. If detected, consult a professional for appropriate treatment options, including insecticide application or tree removal.
Fungal Diseases
Watch for anthracnose, verticillium wilt, and fungal leaf spot diseases. Prune away infected branches and ensure proper watering and fertilization to promote tree health. Apply fungicides as needed, following label instructions.
Ash Rust and Ash Yellows
Address weak trees promptly to prevent yellow-orange spots on leaves or pale green to yellow discoloration. Treat with fungicides or insecticide sprays according to the stage of infection.
Pest Management
Combat aphids, scale insects, and ash sawflies by regularly inspecting for signs like brittle branches and curling leaves. Apply appropriate insecticides or consider natural predators for control.
III. Uses and Benefits
- Urban ornamental trees
Green ash is one of the most widely planted ornamental trees throughout the United States and much of Canada but mostly Alberta, including in western areas where it is not native. It is also widely planted in Argentina. It is very popular due to its good form and resistance to disease. About 40% of boulevard trees in Edmonton, Alberta, are green ash. It is often planted for shade or as a windbreak.
For the last two centuries American elm and ash, which both belong to the ancient Elm-Ash-Cottonwood Bottomland ecosystem, achieved distinction as North America’s two most popularly planted urban species, used primarily for their superior survival traits and slowly maturing 180–300 year majestic natural beauty.
Today used as living national monuments, the National Park Service is protecting Thomas Jefferson’s 200-year-old planted example, and George Washington’s 250-year-old white ash which has a 600-year possible lifespan. Green ash had been widely used as a primary ornamental and long lived monument tree until the elm fad of the 1880s, and regained top position once again after Dutch elm disease arrived.
Other continents learned of American ash species’ urban survivability and unique beauty through the worldwide popularity of Midwestern Prairie style ecology and architectural movement. Modernizing cities in Russia and China then began using imported green ash a century ago to line streets and landscape new public parks.
Advantages of green ash include its tolerance of harsh urban environmental conditions, ease of propagation, and (in eastern North America) its value for wildlife as a native keystone species.
- Utility 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 varieties 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.
- Other uses
Green ash wood is similar in properties to white ash wood, and is marketed together as “white ash”. The commercial supply is mostly in the South. It is very popular, used in making electric guitars because it can be somewhat lighter than white ash without sacrificing too much in tone. It has a bright sound with long sustain, plus the wood grain is aesthetically desirable to many guitar players. Gibson, Fender, Ibanez, Warwick, and many other luthiers use ash in the construction of their guitars.
IV. Harvesting and Storage
If you want to collect green 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 Green Ash (Fraxinus pennsylvanica)
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