FROM LEFT TO RIGHT TOP : Emory oak ( Quercus emoryi ), from the Southwest , main collection ; deer oak ( Quercus sadleriana ), from the Siskiyous , Pacific Connections . CENTER : Cork oak ( Quercus suber ) in the Mediterranean section at the Arboretum ; Holm oak ( Quercus ilex ), from the Mediterranean , south Arboretum Drive . BOTTOM : California black oak ( Quercus kelloggii ), Pacific Connections Garden ; Quercus × bushii ‘ Seattle Trident ’, an Arboretum introduction , main collection .
between 435 and 550 species ( taxonomy being a fraught discipline ). Vying with Pinus as the genus with the greatest biomass in the northern hemisphere , Quercus nevertheless includes scores of endangered and threatened species ( nearly one third in total ) according to the International Union for the Conservation of Nature Red List . Sixteen of the 91 species native to the United States are deemed threatened with extinction . Renewed intensity of seed-collection efforts through the Plant Collections Network aims to ensure that no U . S . species actually goes extinct .
One example is the exceedingly rare mapleleaf oak ( Q . acerifolia ), found only in several isolated locations in Arkansas . The Arboretum received acorns of this taxon two years ago . Another is the Boynton oak ( Q . boyntonii ), which the Arboretum received in 1999 . It is a dwarf species — previously known only in six counties in Alabama — though a field survey sponsored by the APGA in 2020 found a population in a seventh county and was pleased to find nearly 500 individuals across about two-thirds of the species ’ range . ( I stumbled upon the Arboretum ’ s five specimens of Q . boyntonii by chance in some rough brush about 10 years ago — and you might have to follow the same method , as the Collections Database lists the grid-square location as “ Inquire .”)
Ray has other partners in propagation . He has received a number of seedlings and acorn selections from seed exchanges at the triennial conferences of the International Oak Society ( internationaloaksociety . org ). Specialty nurseries that focus on Mediterranean climate and aridity-adapted species have been the source of many recent additions . Far Reaches Farm in Port Townsend has also done some propagation for the Arboretum . And it is a two-way street : Ray participated in a seed-collection expedition to the Siskiyous two years ago with staff from the Kruckeberg Botanic Garden and Heronswood
Garden and is sharing seeds of the Northwest ’ s charming shrubby oaks — deer oak ( Q . sadleriana ), huckleberry oak ( Q . vacciniifolia ), and Brewer ’ s oak ( Q . garryana var . breweri )— with public gardens around the country . ( These species , purchased from the late Mareen Kruckeberg after reading about them in Art ’ s “ Gardening with Native Plants of the Pacific Northwest ,” were the ones that got me going in the oak world and revived my childhood wonder .)
Ray says the Arboretum ’ s nursery currently has specimens of many new oak species growing in large pots . There is a premium to planting out only well-established plants , given the prevalence of rabbits and the unpredictability of human-plant interactions . Ray is currently assessing areas in the oak collection , and other areas with enough sun , for new planting sites and hopes to plant out many in the coming year . Readers , if you see semi-open spaces in the Arboretum with pretty good sunlight and relatively dry soil , check back again to see if Ray and team have taken advantage for the siting of a new oak accession .
How are oaks used for environmental education ? The Arboretum also makes regular use of the oak collection in kids ’ nature classes . The variety of leaves — lobed and entire , bristle-tipped and rounded , stiff and limber , tomentose and smooth , large and tiny — makes it a nice teaching collection . Oaks play an important role in many ecosystems and have a rich history of cultural uses . Nice stimulus for adult brains , too ! It will repay the visitor to connect with the Quercus collection multiple times a year . m
Dirk Giseburt was born in Seattle and works as a tax lawyer at Davis Wright Tremaine . He was briefly a post-baccalaureate undergrad in the old UW Botany Department and is currently on the board of the International Oak Society .
Summer 2021 v 19