White Ash

(Oleaceae - Olive Family)

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• Form
  • large shade tree
  • usually maturing at about 70' tall by 70' wide, but can become much larger
  • upright oval growth habit in youth, quickly maturing to a rounded growth habit without a central leader
  • medium to rapid growth rate

• Culture
  • full sun to partial sun
  • prefers moist, well-drained, deep, slightly acidic soils in full sun, and is somewhat adaptable to various soils and soil pHs, but overall it is not overly urban tolerant (especially to soil compaction and drought), especially when compared to Green Ash
  • cultivars are propagated primarily by cuttings grafted onto seedling rootstock, while the species form is easily propagated by seeds
  • Olive Family, with several noteworthy diseases (leaf anthracnose, leaf spots, branch cankers, mycoplasma-induced decline and dieback) and pests (ash borer, oyster shell scale)
  • abundantly available in ball and burlap form

• Foliage
  • opposite leaves are pinnately compound, to 15" long overall, medium to dark green on the uppersides of the leaflets, and silvery-white to light green underneath, casting a dense shade and a slightly bicolor effect in the breeze
  • leaflets (usually seven, but can be five or nine) are ovate (wider than Green Ash) and usually entire on the margins
  • rachis is stout and enlarged at its base, leaving a prominent crescent moon-shaped (U-shaped) leaf scar upon abscission
  • fall color is often a progression from vivid yellow to orange, maroon, red, and finally burgandy or purple, usually beginning in late September and completely abscised by mid-October (some cultivars may proceed directly from green to the darker reddish colors)

• Flowers
  • the species form is usually dioecious (having separate male and female trees), but most 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 thick, smooth, and very stout lenticeled stems are olive, changing to gray or brown with age
  • leaf scars are distinctly U-shaped (with the U being upright), with a large brown pubescent lateral bud resting within each leaf scar, and a large flattened terminal bud at the end of each stout twig

• Trunk
  • gray-brown bark is very smooth in youth, but becoming very deeply furrowed and ridged in just a few short years, with the ridges interlacing to form a diamondback pattern of 2" thick bark at maturity
  • quickly losing its central leader to yield several large upright to spreading main branches, for a very rounded growth habit

• ID Summary
  • pinnately compound leaves usually have seven leaflets which are entire, in opposite fashion on the stout and thick stems, with leaf scars having a curved, dipping line across the top of the scar
  • growth habit is tightly upright oval and sparsely branching in youth, becoming more rounded with age, with smooth bark in youth becoming a ridged and furrowed, subtlely ornamental, thick bark with age
  • fall color transitions through shades of gold and red and often terminates as red-purple or maroon
  • modern cultivars usually have male inflorescences and are always seedless

• Function
  • shade or specimen tree, possessing great symmetry and stateliness, especially in youth

• Texture
  • medium texture in foliage and bold texture when bare
  • thick density in foliage and average density when bare

• Assets
  • brilliant transition of Autumn colors
  • moderately quick growth, establishment, and shade
  • bold-textured bark, stems, and outline in Winter
  • symmetrically rounded shape at maturity

• Liabilities
  • not especially urban tolerant (although often put into this situation)
  • has the potential for numerous disease and pest problems, with the most serious usually being leaf anthracnose and wood borers
  • dense shade with maturity leads to dead stem litter from the interior of the canopy and turf die-out underneath
  • surface roots and basal trunk flare with age

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

• Alternates
  • shade trees with excellent fall color (Acer rubrum, Acer saccharum, Liriodendron tulipifera, Nyssa sylvatica, Quercus rubra, Zelkova serrata, etc.)
  • shade trees of good quality that grow moderately fast (Acer platanoides, Corylus colurna, Liriodendron tulipifera, Fraxinus pennsylvanica, Gleditsia triacanthos inermis, Quercus acutissima, Quercus shumardii, Ulmus parvifolia, Zelkova serrata, etc.)

• Variants
  • Fraxinus americana 'Autumn Applause' - maroon fall color, male, 40' tall by 25' wide, upright oval at maturity
  • Fraxinus americana 'Autumn Purple' - purple-red fall color, male, 45' tall by 60' wide, yielding a spreading form with glossy Summer and Autumn foliage
  • Fraxinus americana 'Rosehill' - relatively poor yellowish bronzy red fall color, seedless, 50' tall by 30' wide, noteworthy for its tolerance to poor soils that are distinctly alkaline in pH
  • Fraxinus americana 'Skyline' - orange-red fall color, male, 50' tall by 40' wide, often improperly used for street tree plantings due to its sentry-like, columnar growth habit in youth; however, it is more urban tolerant than the species form and most other cultivars

• Translation
  • Fraxinus is the Latin name for Ash.
  • americana translates as "of the Americas".

• Purpose
  • White Ash is a large shade tree of rounded outline with excellent Autumn color and bold Winter texture.

• Summary
  • Fraxinus americana is a shade tree of rounded growth habit and moderately rapid growth rate, having dense Summer shade, an excellent mixture of Autumn colors that usually terminates in burgandy-red, and a bold Winter bark and stem texture, but prone to diseases and pests as it matures.

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