If you love birdwatching and your yard needs some extra shade and color, an American mountain ash tree is the perfect addition to your landscape. Sorbus americana is a compact ornamental tree native to North America. It grows wild throughout the Great Lakes, New England, and the Appalachian Mountains and performs excellently in urban and suburban yards.
The thick clusters of showy white flowers are followed by vibrant red berries, adding aesthetic charm and wildlife value through summer. At the end of the season, its golden-orange autumn leaves captivate a landscape in the fall and the berries remain into winter. Mountain ash averages 15-35 feet at maturity and grows with a nice, rounded, open-top crown. Sometimes, it grows from a single trunk, but it commonly has a shrubby multi-stemmed base.
For gardeners in cool eastern regions from hardiness zones 2-6, this native tree will grow quickly without much fuss. Let’s dig into everything you need to know about growing a mountain ash tree!
American mountain ash has a rich history and intriguing folklore. The plant is one of 7 mountain ash species native to the U.S., and the genus Sorbus includes over 100 or 250 species, depending on your definition of the genus. American mountain ash (Sorbus americana) is smaller and smooth-leaved compared to the larger, hairy-leaved European mountain ash (S. aucuparia). Here are more details of this gorgeous red-berried tree and its origins.
The American mountain ash (Sorbus americana) is an excellent choice for gardens both large and small. This hardy, beautiful tree provides ample shade, seasonal interest, and even edible fruit. Read on to learn more about the benefits of adding American mountain ash trees to your outdoor space.
An Overview of the American Mountain Ash
The American mountain ash is a small to medium-sized deciduous tree, growing 30-50 feet tall and 20-30 feet wide [6]. This native North American tree grows in USDA hardiness zones 3-6, so it thrives in colder climates [6].
The mountain ash gets its name from the similarity of its leaves to those of the European ash tree. However, the two plants are not closely related. American mountain ash trees belong to the rose family. Their foliage consists of oval toothed pinnately compound leaves that turn brilliant shades of orange and red in fall.
One of the biggest draws of the American mountain ash is its spring blooms The tree erupts with dense, flat clusters of creamy white flowers in May or June [6] These blossoms attract pollinators before giving way to bunches of bright red-orange berries in late summer/early fall [6]. The berries often persist into winter, providing great seasonal interest and food for birds.
The Benefits of Planting American Mountain Ash Trees
Here are some of the top benefits you’ll enjoy when planting American mountain ash trees in your yard or garden:
Provides Multi-Season Interest
One major advantage of the American mountain ash is that it offers multi-season interest. Its early summer blooms give way to lush green foliage in summer and striking fall color. The bright fruit clusters add pops of color from late summer into winter [6]. So the mountain ash tree gives you beautiful sights for much of the year.
Attracts Wildlife
The berries of the American mountain ash provide a valuable food source for many birds in fall and winter [6]. Types of birds attracted to the fruit include robins, waxwings, thrushes, bluebirds, cardinals, and finches [6]. Planting this tree will invite more birdlife into your garden for wildlife watching enjoyment.
Provides Dappled Shade
While not an extremely dense shade tree, the American mountain ash does provide some filtered shade thanks to its oval canopy shape [6] This makes it a nice choice for planting over seating areas, play areas, or anywhere you want a mix of sun and shade. The shade cast has a pretty, dappled effect
Has Edible Fruit
As mentioned previously, American mountain ash trees produce clusters of small red-orange berries. While sour when raw, these berries can be cooked and made into jellies, jams, syrups, and even wine [6,21]! So if you enjoy foraging or using edible plants, the mountain ash can be a fun addition to your backyard. Just be sure to do plenty of research first and properly identify the tree.
Works as Windbreak
With their oval form and moderate size, American mountain ash trees are sometimes planted together to form windbreaks [20]. Their foliage helps obstruct and slow winds, protecting crops, livestock, yards, and gardens. If you live in an area with strong winds, a mountain ash windbreak could be beneficial.
Requires Little Maintenance
Once established, American mountain ash trees are quite low-maintenance [6]. They have no serious pest problems, establish with little effort, and need only occasional pruning. The mountain ash grows well in poor soil and is very drought tolerant. All around, it’s a sturdy, resilient tree requiring minimal care and upkeep.
Provides Erosion Control
The American mountain ash’s fibrous roots help hold soil in place, making it a good pick for preventing erosion [6]. Plant it on slopes or other areas prone to soil erosion. As a bonus, this tree tolerates poor, rocky soils well.
Grows in Varied Conditions
One more advantage of the American mountain ash is its adaptability. It tolerates a wide range of soil types, pH levels, moisture conditions, and exposures [6]. Mountain ash trees grow in full sun to partial shade, moist to dry soil, and even cold, windy sites. This toughness makes it suitable for challenging planting areas.
Has Medicinal Uses
Various parts of the American mountain ash tree have been used medicinally by Native Americans for purposes like treating diarrhea, stimulating circulation, and inducing labor [21]. While mountain ash should never be ingested without medical supervision, its historic medicinal uses are interesting.
Provides Fall Fragrance
The sweet, wax-like scent produced by the ripening fruits and foliage of mountain ash trees is an added fall pleasure [6]. On crisp autumn days, take a walk beneath your mountain ash and enjoy its fresh, fruity perfume.
Planting and Caring for American Mountain Ash Trees
If you’re ready to add the beauty and benefits of American mountain ash trees to your property, here are some tips for getting started:
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Pick the right spot – Mountain ashes need full sun to partial shade and well-drained soil [6]. Avoid soggy sites. Give them space from buildings, as they can grow to 30 feet wide.
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Prepare the soil – Improve drainage in heavy soils by mixing in compost. Also work compost into any rocky or infertile soil.
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Plant in spring – The best time for planting mountain ash trees is in spring once the threat of frost has passed [6].
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Water well – Provide new trees with regular deep watering for the first two years. Then they should be drought-tolerant.
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Use mulch – Mulching around mountain ashes helps retain soil moisture and inhibits weeds. Avoid piling mulch against the trunk.
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Prune occasionally – Occasional pruning when young helps mountain ash trees establish good structure. Remove any dead/damaged branches as needed.
Enjoying the Benefits of American Mountain Ashes
The American mountain ash is one of those trees that offers year-round beauty and benefits for nature lovers. From its cascading white spring flowers to its tart edible berries and striking fall color, this North American native is worth finding room for in gardens small and large.
If you like attracting birds, want low-maintenance trees, or enjoy multi-season interest, be sure to consider planting American mountain ash. Let it provide you with shade, erosion control, wind protection, edible fruits, and gorgeous seasonal displays for years to come.
Bare-root or Container Trees
Find trees at local nurseries, available in bare root, balled and burlapped, or containers.
For those seeking young trees that can quickly take off growing in their yard, your local nursery is the best option. Native plant nurseries in the Great Lakes, Northeast, and Appalachian regions are highly likely to carry American mountain ash.
The tree is usually available in three forms:
Young mountain ashes are dug up in their dormant phase and sold without any soil on the roots. They can establish quickly, but are typically smaller.
These trees come with soil around the roots and are often available in fairly large sizes. However, B&B trees sometimes suffer from transplant shock due to losing most of their roots in the digging process. It’s important not to plant them too deeply.
Container-grown mountain ashes are available in 5-25 gallon pots. They are more expensive than bare root, but less likely to experience transplant shock like B&B trees.
When picking out a nursery tree, be sure to consider:
- Size of the root ball: Can you handle planting it on your own or with help?
- Trunk health: Fire blight is a major issue on mountain ash trees, causing visible cankers that look like they’ve been burned. Avoid these plants at all costs.
- Shoots: Do the fresh green shoots grow straight upward? If they are wilted or bending downward in a hook-shape, the plant may have fire blight and should not be purchased.
- Foliage health: Are the leaves vibrant, green, and turgid? Avoid specimens with lots of yellow, wilted, or dead foliage.
- Pests and diseases: Check under the leaves for bugs and smell the root zone to ensure there are no signs of rot.
If you specifically want to plant the native variety, check that the species is Sorbus americana, not Sorbus aucuparia, which is the European variety.
American mountain ash is the perfect plant for a cool-climate front yard, a native plant garden, or an exposed slope. Here’s how to plant the trees and water them properly for a strong growth start.
Plant or relocate mountain ash trees in early spring with full to partial sun and moist soil.
The best time to plant or relocate mountain ash trees is in early spring while they are still dormant. Before planting your seedlings or saplings, be sure that the location has full to partial sun and moist, acidic soil.
To transplant:
- Dig a hole three to four times the diameter of the root ball and about one and a half times the depth of the root ball.
- Use a shovel or pitchfork to loosen the soil along the sides of the hole.
- In heavy clay, amend with horticultural sand or peat moss to improve drainage.
- Place the tree in the hole facing straight up.
- For bare roots, spread the roots so they point down and outward.
- For containers, ensure the soil level remains the same.
- Backfill the soil around the base.
- Avoid planting mountain ash too deep. The bottom roots should be buried, and the base of the central stems should be fully above ground.
- Use the back of a shovel or your hand to create an indented water ring around the outer edge of the hole. This will hold more moisture and encourage perimeter roots to reach outwards.
- Water deeply.
Young trees need a fair amount of moisture, but it’s important that the soil never gets soggy. The key is to water deeply (i.e., enough to fully saturate the newly planted rootball) but less frequently. Use your hand to check that the first round of irrigation has penetrated the soil at least 6-12 inches deep.
Mountain ash grows as a large shrub or small tree, needing 10-30 feet of space.
Sorbus americana grows as a large multi-stemmed shrub or a small single-trunk tree. It requires at least 10 feet of space from other trees and shrubs. You can space them up to 30 feet if you’d like the tree to grow to its maximum height and spread.
This northeastern-native plant is easy to grow in cold climates from USDA 2 through 6. It takes off readily in the northernmost parts of its native range but may require a little more tending in urban environments. Overall, the tree is easy to grow and rewards you with one to three feet of annual growth. You can expect pretty umbel flowers and vibrant red berries after a few years of maturity.
Site in a spot with full sun for optimal growth.
American mountain ash prefers full sun, but it will tolerate partial shade. The tree naturally grows on open slopes as well as open forest understories. It needs at least 6 hours of sunlight and enjoys more in its northern range. Maximum sunlight ensures faster growth and an abundance of flowers and berry clusters. In zones 6 and 7, it will appreciate dappled sunlight in the afternoon.
This native species thrives in moist forests, requiring deep watering but avoiding standing water.
Moisture is key for this native species. It loves the wet forests of New England and the Great Lakes. The trees struggle in dry climates and appreciate extra irrigation during times of drought. However, they do not tolerate standing water or soggy clay soils.
It’s best to water your tree deeply but less frequently. In well-drained soil, generously soak around the root zone and check that water penetrates 6-12” into the soil.
As the trees get established, they can often subsist on the rainfall off their native cool mountain climates. If growing in a suburban or dryer environment, supplemental irrigation is essential.
This tree prefers acidic, well-drained soil enriched with sand, peat moss, and compost.
Mountain ash grows best in acidic, humus-rich, well-drained soil. Amending with sand, peat moss, and compost can improve conditions before planting. Waterlogged clay soil or dry, cracked soil will result in poorly performing, ugly trees that are more susceptible to pests and diseases.
Cool, mountain climates provide the ideal growing environment.
American mountain ash is hardy in USDA zones 2-6 and thrives in cool mountainous climates. It enjoys the damp chill of Northeastern forests, where it grows alongside cold-loving balsam fir, American yew, and woodfern.
This shrubby tree will not grow well in regions with hot, humid summers or dry soils. Avoid planting it in southern zones and areas with high urban pollution.
Native mountain ashes require minimal fertilizer in humus-rich soil to avoid issues.
Mountain ashes are not heavy feeders. In humus-rich soil, little to no fertilizer is needed for this native species. Excessive nutrients can cause problems with insect outbreaks and diseases, so it is especially important to avoid concentrated quick-release fertilizers.
Minimal maintenance involves leaving fallen leaves for soil or compost and pruning as needed.
Little to no maintenance is needed to keep these trees happy and beautiful. After the trees drop their leaves in fall, you can leave them in place to nurture the soil or rake them up and add them to your compost pile. If lower stems become scraggly or diseased, prune them away in late fall to early spring while the tree is dormant.
The Sorbus genus contains over 100 or 250 species of trees and shrubs around the world, with a large concentration in Europe and North Africa. Many different species of mountain ash go by the nickname “Rowan tree.” Interestingly, American mountain ash trees are known to naturally hybridize with chokecherry shrubs (Pyrus melanocarpa and P. floribunda) in the wild. But in the world of ornamental landscaping, these three species are the most commonly available:
American Mountain Ash (S. americana)
Native to the Northeastern U.S. and Canada, this tree is prized for autumn color.
This is the native species found growing wild throughout the Northeastern United States and up into Canada. It has an attractive form and is prized for its autumn and winter color in the garden. Do not plant it anywhere with insufficient moisture, or the trees will suffer.
The Rowan Tree – Wild Food, Health Benefits & Mythology (Mountain Ash)
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