May 18 is celebrated around the world as Plant Conservation Day. Because botanists estimate that one in five plants are threatened with extinction globally, botanical gardens and arboreta play a critical role in preserving and sharing the germplasm of plants collected in the wild. Plant conservation is important at the Arboretum, where we collect, cultivate, and document as many threatened and endangered plants as possible.
How does the Arboretum know which plants are threatened globally? An important part of our work includes an annual assessment of our accessioned plants to determine which are of conservation concern. We just completed the audit and report that 12% of the plants growing in the Arboretum—over one thousand individuals—are currently threatened in the wild. Armed with the knowledge of each plant’s conservation status, we apply it in many ways, asking and answering questions such as: Do certain plants need special care, or repropagation? Should we return to the wilds and collect more germplasm? Can we promote them to researchers to make new discoveries? There are many research questions to pose and any study conducted on these plants increases our understanding of how these species function and how we can best conserve them.
When you visit the Arnold Arboretum—as a visitor, student, educator, or scholar—you will encounter many plants that are disappearing from around the globe. A number are celebrated for their beauty and seasonal interest but also happen to be threatened: these include ginkgo (Ginkgo biloba) which populates streets, gardens, and arboreta all over the world but is rarely found in the wild; and the late summer flowering Franklin tree (Franklinia alatamaha) which is now extinct in the wild and today only found preserved in cultivation. It is important to note that many lesser-known species of concern also grow in the Arboretum landscape, such as these three interesting ones:
Quercus acerifolia: Native to the United States (Arkansas), the maple-leaf oak is one of the most threatened trees in the United States. This beautiful oak was first discovered in 1926 by Arboretum botanist E. J. Palmer, one of the Arboretum’s most prolific collectors. It was collected by the Arboretum more recently in our 2014 Expedition to the Ozarks led by Keeper of the Living Collections Michael Dosmann. Oaks have recalcitrant acorns which lose their viability when dried, which means that they cannot be preserved in a seedbank. Therefore, growing trees in living collections is an important strategy for preserving this threatened and historically significant species.
Pyrus korshinskyi: This species of pear, native to the Republic of Kazakhstan and globally threatened, grows in only a few remaining (and isolated) locations. Because it is a relative of the common pear we eat today, this species (known as a crop wild relative) is an important genetic resource in the fight against newly emerging plant diseases. This underlies the importance of preserving genetic diversity for the species itself and for future cultivation and hybridization. In situ (in the wild) conservation efforts are ongoing, but ex situ conservation is another important way to safeguard these plants for future study and distribution.
Syringa josikaea: Included in one our Plant Collections Network (PCN) collections (Syringa), this species is native to Transylvania and Ukrainian Carpathians and is listed as globally threatened. This delicate and beautiful lilac has a limited distribution in the wild, with threats including natural habitat disturbance such as agriculture, road construction and logging. This lilac grows well in full sun to partial shade, and moist, well-drained, slightly acidic soil. It produces purple blooms in late May to early June, which means there is still time for visitors to see this threatened species in full bloom in the Arboretum’s collections!