Fraxinus profunda
Fraxinus profunda, the pumpkin ash, is a species of ash native to eastern North America, where it has a scattered distribution on the Atlantic coastal plain and interior lowland river valleys from the Lake Erie basin in Ontario and New York west to Illinois, southwest to Missouri and southeast to northern Florida. It grows in bottomland habitats, such as swamps, floodplains and riverbanks. It is threatened by the emerald ash borer, an invasive insect which has caused widespread destruction of ash trees in eastern North America.
Taxonomy
Pumpkin ash is a member of the olive family and is placed in section Melioides of the genus Fraxinus. Historically, it was frequently called Fraxinus tomentosa Michx., but since Michaux used this name interchangeably with the species now known as green ash, the name Fraxinus profunda, which was applied by Benjamin Franklin Bush in 1901, was given precedence.Pumpkin ash is hexaploid and has been hypothesized to have originated as a fertile hybrid between green ash and white ash, but this remains unproven.
The name pumpkin ash originates from early European settlers in Arkansas and refers to the swollen trunk bases which this tree often produces in very wet habitats.
Morphology
Pumpkin ash is a medium-sized deciduous tree reaching tall with a trunk up to 1 meter in diameter, although exceptional trees can reach tall with a diameter trunk. Important morphological characteristics of pumpkin ash include:- bark: gray, thick and fissured with a diamond pattern on mature trees
- buds: dark brown to blackish, with a velvety texture
- leaves: long, oppositely-arranged, pinnately compound with 7 to 9 leaflets; leaflets long and broad, with smooth or obscurely serrated margins and short petiolules; abaxial surfaces are tomentose and lack a dense covering of papillae
- flowers: wind-pollinated, purplish-green, lacking a corolla; borne in panicles; blooming in spring shortly before the emergence of leaves
- fruit: samaras long, comprising a single seed with an elongated apical wing broad.
Pumpkin ash trees frequently produce bulbous swollen trunk bases and this is sometimes cited as a diagnostic feature of this species. However, not all pumpkin ash trees exhibit this feature and other ash species, such as green ash, can also produce swollen trunks in very wet habitats.
Reproduction
Pumpkin ash attains sexual maturity and begins producing fruit at approximately ten years of age. The seeds develop during the summer and are dropped in the early fall. The winged samaras are adapted to wind dispersal, but pumpkin ash seeds are uniquely adapted to dispersal by water and can survive submersion for several months.Seedlings thrive in moist soils in canopy openings and are sensitive to shade. Young trees are extremely fast growing and can quickly attain a height where they compete with mature trees.
Ecology
Pumpkin ash occurs primarily in swamps, floodplains and other wet bottomland habitats. Along with other ashes, it is a food plant for the larvae of several species of Lepidoptera.Pumpkin ash is threatened by the emerald ash borer, an invasive insect which has destroyed large numbers of ash trees in eastern North America. In 2017, the IUCN assessed the pumpkin ash as Critically Endangered, due to observed massive population declines over most of its range. In 2021, pumpkin ash was listed as endangered in Canada under the Species at Risk Act, 2002.