Green Ash

(Oleaceae - Olive Family)

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• Form
  • large shade tree
  • generally maturing at 50' tall by 30' wide, but can become much larger
  • upright oval growth habit in youth, becoming rounded or sometimes irregular in growth habit with age, without a central leader
  • rapid growth rate

• Culture
  • full sun to partial sun
  • prefers moist, well-drained soils in full sun, but is very adaptable to poor soils, rocky soils, various soil pHs, compacted soils, wet sites, dry sites, pollution, and Winter salt spray (extremely urban tolerant)
  • modern cultivars are propagated by cuttings grafted onto seedling rootstock; while the species form is easily propagated by seeds
  • Olive Family, with several disease and pest problems (including oyster shell scale and ash borer), but less severe than in other Ashes
  • abundantly available in ball and burlap form

• Foliage
  • leaves are opposite, medium to dark green, slightly shiny, and pinnately compound, up to 1' long
  • leaflets (usually five, but sometimes seven or nine) are usually serrated (but are sometimes nearly entire) on the margins and are narrow-ovate
  • fall color is often poor and a mixture of green and chartreuse in late September and October, but can be a bright golden-yellow in good years

• Flowers
  • the species form is usually dioecious (having separate male and female trees), but all modern cultivars are seedless (being almost exclusively male selections)
  • green to purple inflorescences in April are ornamentally insignificant

• Fruits
  • on female trees of the species form, fruits are green changing to brown, in prolific clusters of samaras, with the winged seeds littering the ground or falling into gutters in Autumn
  • modern cultivars are seedless, being predominantly male clones

• Twigs
  • the stout and smooth but relatively thin stems (as compared to White Ash) are olive-colored, changing to gray-brown with maturity, and lenticeled
  • leaf scars are half-moon-shaped (or "D" shaped, with the "D" laying on its side and the flat portion on top) with a brown pubescent bud sitting directly on top of the flattened leaf scar
  • lower branches often become pendulous with age and turn upward at the branch tips

• Trunk
  • gray-brown bark is composed of flaky thin strips in youth, becoming deeply furrowed and ridged with age, with the ridges interlacing to form a diamondback pattern

• ID Summary
  • pinnately compound leaves usually have five leaflets which are subtlely serrated, in opposite fashion on the stout but relatively thin stems, with leaf scars having a flat line across the top of the scar
  • growth habit is tightly upright oval and twiggy in youth, becoming more spreading, open, pendulous, and/or irregular and densely twiggy with age, with flakey strips of bark in youth becoming a ridged and furrowed, subtlely ornamental, thick bark with age
  • fall color is chartreuse to golden, and usually not impressive
  • modern cultivars usually have male inflorescences and are always seedless

• Function
  • shade tree (often for difficult sites) or wet site tree
  • often utilized as a street tree or parking lot island tree due to its extreme urban tolerance (and is more compact in its growth in these situations), but surface roots may eventually cause a problem by buckling the concrete or asphalt if it is not removed before maturity

• Texture
  • medium texture in foliage and medium-bold when bare
  • thick density in foliage and when bare (at maturity)

• Assets
  • quick growth, establishment, and shade
  • extreme urban tolerance (including tolerance to very poor soils, very dry sites, poor drainage, and Winter salt tolerance)
  • moderately ornamental bark at maturity

• Liabilities
  • surface roots with age
  • interior shading leads to dead stem litter with age, and overall shade leads to turf die-out under mature trees that have not been significantly limbed up
  • prone to some disease and pest problems, some surface roots, and some storm damage (due to slightly brittle wood), all with age and maturity

• Habitat
  • zones 3 to 9
  • native to the Eastern and Midwestern United States and Southern Canada

SELECTIONS

• Alternates
  • rapidly growing shade trees for areas with moderate to severe urban stress (Acer x fremanii, Corylus colurna, Ginkgo biloba, Gleditsia triacanthos inermis, Platanus x acerifolia, Quercus rubra, Ulmus x 'Urban', etc.)

• Variants
  • Fraxinus pennsylvanica 'Cimmaron' - a new male introduction with the potential to revolutionize this species with the bonus of good fall color, having a sequence of burgandy to brick red to orange fall color (probably with a Red Ash heritage in its genetic makeup), to 60' tall by 30' wide
  • Fraxinus pennsylvanica 'Marshall's Seedless' - male, lustrous dark green foliage, to 50' tall by 40' wide, with yellow fall color
  • Fraxinus pennsylvanica 'Patmore' - male, glossy dark green foliage, to 45' tall by 35' wide, zone 2 hardiness, more uniform upright branching and oval character than the species form or many cultivars
  • Fraxinus pennsylvanica 'Summit' - seedless form, glossy medium green foliage, to 45' tall by 25' wide with a pyramidal to upright oval growth habit, better yellow fall color than species form or many cultivars
  • Fraxinus pennsylvanica 'Urbanite' - seedless form that probably has a lot of White Ash in its genetic background (stout stems, crescent leaf scars, entire leaf margins, thick dark green leaves, smooth young bark), being extremely vigorous in its growth and with a yellow-bronze fall color, to 50' tall by 40' wide

• Translation
  • Fraxinus is the Latin name for Ash.
  • pennsylvanica translates as "of Pennsylvania".
  • formerly, Green Ash was classified as Fraxinus pennsylvanica lanceolata, while Red Ash was classified as Fraxinus pennsylvanica; both are now combined into the same species.

• Purpose
  • Green Ash is an urban tolerant and rapidly growing shade tree that, along with Thornless Honeylocust (Gleditsia triacanthos inermis), is successfully used in very stressful urban situations (including restricted root zone areas with poor rocky clay soils that are exposed to Winter salt spray).

• Summary
  • Fraxinus pennsylvanica is a common upright oval to rounded shade tree of rapid growth and establishment, having yellow to chartreuse fall color and widely planted due to its quick shade and excellent adaptability to urban stresses.