The Arnold Arboretum is a living museum, displaying plants collected from all corners of the temperate world for conservation, study, and enjoyment. The 281-acre landscape displays some 2,100 species, represented by some 15,000 trees, shrubs, and vines. While some of these plants are of garden or nursery origin, others have been gathered directly from the wild, bringing with them the unique characteristics and genetic makeup of the source population. Knowing a plant’s origins is an important factor in fostering its potential for research, and is also essential for conservation efforts. As such, the Arboretum routinely conducts and participates in plant exploration throughout temperate Asia and North America to acquire new species and new populations of plants hardy in Boston.
During the first week in October, the Arboretum joined the Morris Arboretum (University of Pennsylvania) and the Polly Hill Arboretum (Martha’s Vineyard) on a plant collecting expedition to Arkansas. The team comprised Arboretum Curator of Living Collections Michael Dosmann, Tony Aiello (Director of Horticulture and Curator at the Morris), and Tim Boland and Ian Jochems (Executive Director and Horticulturist, respectively, at Polly Hill). Working with Arkansas Natural Heritage Commission Botanist Theo Witsell, the team explored a number of state and national parks as well as private lands. Their focus for the trip was the flora of the Ozark and Ouachita Mountains, which is considerably rich due to the diverse geology of the region, coupled with the fact that it did not experience glaciation like northern areas of North America.
“This trip was quite a success,” Dosmann noted. “I was excited to botanize an area that had been explored by the Arboretum a century ago.” While the Arboretum’s plant exploration history in eastern Asia may be well known, the institution’s significant role in documenting the flora of Arkansas and its northern neighbor Missouri may come as a surprise. Founding Director Charles Sprague Sargent and particularly Arboretum botanist Ernest J. Palmer feature prominently in the botanical exploration and documentation of the region during the late nineteenth and early twentieth centuries.
This fall’s expedition yielded collections of 34 plant species of high importance to the participating arboreta. The Arnold Arboretum added six new genera and 13 new species to its collections, each targeted for specific collections, research, and conservation goals. One genus new to the Arboretum is Planera, a relative of the elms (Ulmus) which contains a single species (Planera aquatica) found in low-lying, wet areas–giving rise to its common name, water elm. “This species has been on our target list for years,” Dosmann said, “and it escaped my grasp last year on my collecting trip to southern Illinois. Obtaining it this time might be the highlight of the trip.” An additional 16 acquisitions represent species currently growing in the collections yet without any representatives of documented wild origin.
The expedition also enabled participants to monitor and collect the maple-leaved oak, Quercus acerifolia. Initially described by Palmer as a variety of Q. shumardii (Shumard oak), it has since been raised to species level and is considered one of the rarest oaks in North America, limited to a few hundred individuals in just four populations in Arkansas. Unlike plants with seeds that can be dried and stored for long periods of time, oak acorns are recalcitrant, meaning they cannot be stored. Therefore, the only option for preservation beyond their native habitat is to grow them in gardens and arboreta. The group’s collection of acorns from this trip will be propagated and planted to provide further insurance against this species’ loss.
“Nearly a century and a half into our history,” said Arboretum Director William (Ned) Friedman, “the Arnold Arboretum continues to be at the forefront of plant exploration, the documentation of plant biodiversity, and the collection and propagation of rare and endangered species. As always, if one doesn’t have the time to voyage off into the Ozark and Ouachita Mountains or journey to Hubei Province in China, the Arnold Arboretum is the most wonderful place to see many of the trees, shrubs, and vines of the temperate world all in one place.”