Leatherleaf mahonia poses significant environmental concerns outside of its native range. Photo by: Elena S. via iNaturalist

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Leatherleaf mahonia (Mahonia bealei, syn. Berberis bealei) is an exotic species commonly used as an ornamental plant in homes and gardens. However, this invasive plant has escaped cultivation and is spreading into Pennsylvania’s natural areas, where it can negatively impact native ecosystems.

Background

Leatherleaf mahonia, also known as Beale's barberry, belongs to the barberry family (Berberidaceae). It is an evergreen perennial shrub native to southern and central China. Following its introduction to the United States for horticultural purposes, this species escaped cultivation and began invading natural areas. Today, it continues to expand its range across the country, particularly in the southeastern United States.

Leatherleaf mahonia’s branch with fruits — Leatherleaf mahonia occurs in fewer than 1/3 of Pennsylvania counties, making it an emerging invader. *Photo by: Dan Vickers via iNaturalist*

Concerns

Leatherleaf mahonia may act as a rapid invader, with its clonal growth and abundant seed production allowing it to establish dense thickets. In turn, this species can shade out and displace native vegetation. Additionally, deer tend to avoid eating this plant, potentially leading to increased browsing on remaining native species. Leatherleaf mahonia's dense growth and extensive ground cover may even make habitats difficult for wildlife to navigate.

Dense growth form of leatherleaf mahonia in a forest. *Photo by: User “Amy” via iNaturalist*

Description

Size

Growing 4 to 10 feet tall and 3 to 8 feet wide, leatherleaf mahonia is a medium-sized, woody, evergreen shrub. This species has a relatively slow growth rate.

Leatherleaf mahonia branch with fruits — Growth form of leatherleaf mahonia. *Photo by: User "jaclyn888" via iNaturalist*

Leatherleaf mahonia hidden in a dense woodland environment. *Photo by: Ron Wertz via iNaturalist*

Leaves

Dark to olive-green leaves are pinnately compound, with 5 to 8 pairs of oblong to lance-shaped leaflets and a single terminal leaflet. Individual leaflets are 3- to 6-inches-long and 1 to 3 inches wide, with stiff, spiny margins. The compound leaves are 1 to 1.5 feet long and radiate outward from the stem, creating a distinctive tiered appearance.

leatherleaf mahonia spiny leaflets. — Spiny leaflets are directly attached to the stem. *Photo by: Fred Gibbs via iNaturalist*

Leatherleaf mahonia leaf — Opposite pairs of leaflets with a single terminal leaflet. *Photo by: Fred Gibbs via iNaturalist*

Flowers

Leatherleaf mahonia blooms in late winter to early spring, producing showy, fragrant, lemon-yellow flowers. The flowers are arranged in 3- to 6-inch-long racemes at the top of the plant.

Fruit

Fruiting occurs in late spring to early summer. The showy, 0.5-inch berries are initially green and mature to bluish purple. Fruits hang in clusters and may have a whitish coating. While not considered poisonous, the fruits may cause stomach upset if ingested by humans, particularly children.

Leatherleaf mahonia’s distinct grape-like berries — Leatherleaf mahonia's distinct grape-like berries. *Photo by: User “aliwoody” via iNaturalist*

Stems and Bark

Unbranched stems are rounded, smooth (glabrous), and grayish-brown in color. The bark is light brown and woody.

Coarse brown bark of leatherleaf mahonia. *Photo by: User “louanne_maes” via iNaturalist*

Dispersal

Numerous bird species feed on the fruits of leatherleaf mahonia, facilitating seed dispersal over long distances. The plant can also spread locally through suckers that emerge from the parent plant's roots, promoting colony formation.

American robin (Turdus migratorius) feeding on leatherleaf mahonia — The American robin (*Turdus migratorius*) is one of many native bird species that assist in the spread of leatherleaf mahonia. *Photo by: Michael Newlon via iNaturalist*

Habitat and Distribution

Leatherleaf mahonia prefers shady environments with moist, acidic, well-drained soils. It often establishes in areas with limited sunlight, including woodland and forest understories. It can also be found in semi-disturbed areas, such as old homesites and urban woodlands. This species is somewhat tolerant of drought and high salinity.

As an emerging invasive species in Pennsylvania, leatherleaf mahonia has confirmed occurrences in the southeastern portion of the state. Beyond Pennsylvania, wild populations have been documented from New York south to Florida and as far west as Texas.

Current leatherleaf mahonia distribution in Pennsylvania: Cumberland, Berks, and Chester Counties — Map: Current leatherleaf mahonia distribution in Pennsylvania. *Data sourced from iMapInvasives and EDDMapS*

Look-Alikes

Oregon grape (Berberis aquifolium, syn. Mahonia aquifolium) is another Mahonia species that may be confused with leatherleaf mahonia. While native to western North America, it is considered exotic in the eastern United States. The two species can be distinguished by the veins on their leaflets. Oregon grape has a single prominent vein running from the base to the tip of each leaflet, while leatherleaf mahonia has at least three distinct, less prominent veins.

Oregon grape branch with leaves and fruits — The leaves, fruits, and growth form of Oregon grape resemble its relative, leatherleaf mahonia. *Photo by: Marita S. via iNaturalist*

Single thick vein on the underside of Oregon grape leaflets. *Photo by: Isabella Orellana via iNaturalist*

American holly (Ilex opaca) may also resemble leatherleaf mahonia because of its leathery, spiny leaves. However, American holly has simple leaves that are alternately arranged along woody branches, while leatherleaf mahonia has compound leaves with numerous pairs of opposite leaflets. Additionally, American holly produces small white flowers and red berries in the leaf axils, in contrast to the yellow flowers and bluish-purple berries of leatherleaf mahonia.

American Holly branch with red berries — Red berries of American Holly, a feature not present in leatherleaf mahonia. *Photo by: User "Alimirth" via iNaturalist*

American Holly’s spiny, leathery leaflets — American Holly's spiny, leathery leaflets occur in an alternate arrangement. *Photo by: Alex Uematsu via iNaturalist*

Native Alternatives

Many native trees and shrubs can provide similar ornamental appeal to leatherleaf mahonia while also offering valuable resources for wildlife. Native alternatives include:

American barberry (Berberis canadensis)
American witch-hazel (Hamamelis virginiana)
American holly (Ilex opaca)
Winterberry holly (Ilex verticillata)
Inkberry (Ilex glabra)
Northern spicebush (Lindera benzoin)

Management

Residential Areas

Control of leatherleaf mahonia begins with prevention. Rather than planting this species as an ornamental, property owners should consider the plants listed in the "Native Alternatives" section above, which can provide similar ornamental qualities while benefiting native wildlife.

Physical control can include hand-pulling seedlings or using a weed wrench to remove larger plants when the soil is moist. Removed fruits should be collected and either burned where permitted or securely bagged and disposed of to prevent seed dispersal. Gardening gloves, long-sleeved clothing, and eye protection should be worn to help prevent injury from the plant’s spiny leaves.

In residential settings, chemical control may include systemic herbicides containing active ingredients such as glyphosate or triclopyr. Depending on the product label, treatment methods may include foliar, cut-stump, or stem applications. Careful application is essential to minimize damage to surrounding desirable vegetation. Always read and follow all herbicide label directions, including application rates, timing, required protective equipment, and site restrictions. When treating plants near property boundaries, communicate with neighbors and take precautions to prevent herbicide from contacting adjacent properties or desirable vegetation.

Non-Residential Areas

The growing season, from late winter through early summer, is generally the optimal time for foliar herbicide applications because the plant is actively growing and can more effectively absorb and translocate the herbicide.

Questions about herbicide product recommendations, effective application techniques, and other management considerations can be directed to the Penn State Extension office in your county.

This article was prepared by Corinne with support from the Great Lakes Restoration Initiative (GLRI), which provides funding for her work.