History
Meet Mahonia
There is a new plant for Washington, DC-area gardeners to consider: Mahonia sps., otherwise known as Berberis sps. The time is right to take a fresh look at this genus.
Attributes
Spineless Mahonia doesn’t mean without a backbone. Narrow-leaved Mahonia doesn’t mean the spines are gone. Orange-leaved Mahonia makes the message clear for the designer, the gardener, and the appreciator. Traditionally, Mahonia has meant prickly, broadleaf evergreen shrubs, with a quirky, overall rough, textured look. Dark-green, horizontally held leaves attach in a whorl down the stalk. Each leaf consists of pairs of spiny, holly-like leaflets attached along the central, often red, extended stalk (it can be over a foot long), ending in a terminal leaflet. New growth often starts with light shades of greens, and cold weather brings out a range of colorful bronze, burgundy, orange, and red leaves. Mahonia’s rhizomes send up shoots that spread slowly but inexorably, while birds spread the seeds indiscriminately. It is highly recognizable once identified. You may, in fact, encounter it on a walk in a local park (sightings have been reported at both Wolf Trap Park in Fairfax, VA, and Rock Creek Park in DC). 14
WASHINGTON GARDENER MARCH 2018
Leatherleaf Mahonia at the Smithsonian's Ripley Garden, Washington, DC.
By Judith Mensh
In 2012, the Exotic Plant Management Team of the National Capital Region National Park Service wrote an “Invasive Plant Alert for Leatherleaf Mahonia (Mahonia bealei),” identifying it as invasive throughout the southeast. While M. bealii invades the southeastern U.S., M. aquifolium—long a popular garden shrub in Europe—has created equal concern, with widely established populations in the forests of eastern Germany. British hedgerows reportedly include naturalized Mahonia aquifolium among their plant community. These two species of Mahonia are poster seedlings for scientists who work on understanding the how and why of plant invasions. In 2018, there are new choices. New cultivars include disease resistance, non-invasiveness, color variations and intensity, narrow prickly leaves, narrow soft leaves, tall growth yet ground-hugging, shade-adapted and drought-tolerant once established Look for fragrant yellow flowers in winter and colorful blue/purple edible berries in spring. A wildlife-friendly plant, Mahonia offers color, fragrance, nectar, pollen, berries, and shelter. It’s also gardener-friendly: Its tough, (usually) spiky leaves deter deer browsing. With both color and scent, it attracts insect pollinators, while its spring berries attract birds and small animals.
Mahonia (Berberis) exemplifies the phenomenon of disjunct biogeography, observed in many instances of flora and fauna: In this case, the East Asia-Northwest America/Mexico/Central America connection, where the same genus, with individualized species, is found in unconnected locations on the planet. The mid-20th–century discovery of intergeneric crosses between Mahonia and Berberis, named x Mahoberberis, caused a reconsideration of the validity of the two taxa being separately named, and the challenge to reabsorb Mahonia into Berberis continues today. Two of these naturally occurring hybrids (xMahoberberis aquisargentii and xMahoberberis meithkeana) can be found through Internet sites, but not for any particular reason (and there are no recommendations from Michael Dirr). Mahonia’s designation as a separate genus was the result of friendship and admiration, rather than science: to pay homage to Bernard M’Mahon (1775– 1816), the man who mentored Thomas Jefferson in the garden, opened the first American seed store, and was one of only two entrusted with curating the botanic collection of the Lewis and Clark expedition; Berberis was named by Linnaeus (1753), and used by Lewis in his notes. All Mahonia are members of the family Berberidaceae. As deserving as M’Mahon is, historically, a new biography and a garden named after him might be more appropriate, since today we have a genus with two scientific names. The two versions are commonly given as synonyms in current references to Barberry and Mahonia, one appearing in parentheses alongside the other; for example, Berberis aquifolium (Mahonia aquifolium). The Asian Mahonia and the American native Mahonia both arrived in commerce about the same time—in the early 19th century—and gained popularity here and in Europe. Mahonia aquifolium is well-known to the indigenous peoples of northwestern USA, who used it to make everything from yellow dyes for baskets and paints to a restorative tea from shaved roots. They also enjoy its edible berries. Its deep-yellow dye combines well with other dyes for greens and oranges, and