green ash (Fraxinus pennsylvanica)
Fraxinus pennsylvanica var. pennsylvanica Marshall
Fraxinus pennsylvanica var. subintergerrima Vahl.
CONFIRMATION STATUS: Confirmed.
TAXONOMY: The currently accepted scientific name of green ash
is Fraxinus pennsylvanica Marsh. This review will not distinguish
between green ash varieties as they are not recognized consistently,
and many systematists do not consider them valid taxa. Hybridization
does not seem to be significant with green ash.
NATIVE STATUS: Native, United States and Canada.
GENERAL BOTANICAL CHARACTERISTICS: Green ash is a
deciduous tree with high branches and a slender growth form. It grows
to 100 feet (40 m) in the southern part of its range but is typically half
that height in the northern portion of its range. Some research indicates
height differences across the east to west range of this species as well.
Trees found in New York are typically greater than 100 feet (30 m) tall,
while those in South Dakota rarely exceed 49 feet (15 m). South Carolina's
state champion green ash tree grows in the bottomland hardwood flood-
plain forest of Congaree National Park and was last measured in 2002.
This tree was 143 feet (43.6 m) tall, and had a crown spread of 96 feet
(29 m) and a circumference of 181 inches (460 cm). The 2004-2005
National Tree Register reports that the national champion green ash tree
grows in Cass County, Michigan, and is 95 feet (29 m) tall, 259 inches
(658 cm) in circumference, and has a 95-foot (29 m) canopy spread. This
tree was last measured in 1995.
The trunk of green ash trees is large and straight. When subjected to
prolonged periods of flooding, trunks may become enlarged at the base.
Under dry conditions, the outer bark is between 5 and 7 mm thick at
breast height, while the inner bark measures a thickness of 1.5 to 2.5 mm.
Green ash leaves are opposite, odd-pinnately compound, and measure
between 4.3 and 12 inches (11-30 cm) long by 3 to 7.1 inches (8-18 cm)
wide. Commonly there are 5 to 9 leaflets that are typically 2 to 4 inches
(6-10 cm) long and 2 to 5 cm wide. Though thin, leaflets are "firm and
leathery". Flowers appear before the leaves and are borne on old wood.
Female flowers are short, dense panicles with 200 to 300 flowers per
panicle. Trees as small as 20 to 30 feet (6-8 m) tall with dbh of 3 to 4
inches (8-10 cm) have produced flowers. However, abundant flowers
are not produced until trees are approximately 8 to 10 inches (20-30 cm)
in diameter . The fruit is a single-seeded, winged samara measuring 10 to
15 mm long. Seeds are small.
The rooting depth of green ash on fine-textured soils is described as
shallow, between 5 and 10 feet (2-3 m). Although the root system is
considered extensive, green ash trees may topple with high winds.
Green ash is dioecious. Researchers have found that the crown of male
trees are generally rounder, broader, and fuller than female tree crowns.
However, researchers have also found that female trees had significantly
greater shoot length , greater lateral shoot length, and a greater number
of lateral shoots than male trees.
Green ash trees exhibit a high level of phenotypic variation, and many
researchers have highlighted differences in the growth rate, survival,
drought tolerance, appearance, and cold tolerance of green ash seedlings
grown from seed collected in northern vs. southern and eastern vs.
REGENERATION PROCESSES: Green ash reproduces both through
seed production and vegetative sprouting. There seems to be a heavy
reliance on vegetative regeneration and decreased production of seedlings
by green ash trees recovering from fire.
Flowers are wind pollinated; the majority of pollen produced travels 25 to
50 feet (7.6-15 m) from the source tree. Male flowers mature earlier than
female flowers, and female flowers are receptive from the time of bud
opening to the time the stigma withers. Female receptiveness lasts 7 to 10
days for individual trees and 2 to 3 weeks for populations. Some have
observed green ash trees just 7 years old and 12 feet (3.7 m) tall flowering,
but typically flowering occurs after trees reach 3 to 4 inches (8-10 cm) in
diameter and/or a height of 20 feet (6 m).
Green ash trees are dioecious with male and female flowers on separate,
wind-pollinated trees; outcrossing is mandatory and the potential for
genetic exchange is great.
White ash trees produce good seed crops every 5 or more years, good
seed crops are produced every year by green ash . Wright reported a high
percentage of male and female flowers each year and a high percentage of
annual seed production by female trees.
Green ash seeds are primarily dispersed by wind but movement by water
is also likely. Animals cache ash seed, which may subsequently germinate
The dispersal distance of green ash seeds is dependent on season and time
since seed shed. Seeds shed in the winter potentially move great distances
from the source on frozen surfaces; seeds dropped in the fall typically rest
near the parent tree. Ash seeds may travel 300 feet (100 m) or more from
the parent tree.
The length of time green ash seed remains viable in the soil likely depends
on site conditions including temperature, flooding, and/or soil type. Ash
seeds are viable for up to 3 to 4 years in the seed bank.
Green ash seed requires cold stratification to germinate. Seeds dispersed
in the fall and winter germinate the following spring. The embryos of newly
fallen green ash seed are dormant. Temperatures near 40 °F (5 °C) are
optimal for endosperm digestion, and germination is encouraged at daily
temperatures alternating between 70 and 90 °F (20-30 °C).
Green ash seeds can also germinate in flooded conditions and other
research indicates that moisture affects seed viability and germinability.
The moisture content of green ash seeds was influenced by late fall
Green ash seedlings establish best in partially shaded sites with moist
soil or litter the ideal soil temperatures for green ash seedling growth is
above 61 °F (16 °C). Green ash seedling growth increased with increasing
soil temperatures from 50 to 70 °F (8-20 °C).
Green ash is capable of producing root crown and epicormic sprouts,
and both are typical following disturbances. Many report "prolific" and
"vigorous" root crown sprouting following fire, logging, or other events
that damage the trunk and seems to be a reliance on asexual regeneration
on sites where the likelihood and/or frequency of flooding disturbance is
SITE CHARACTERISTICS: Green ash is most often described in
association with riparian areas, floodplains, and swamps, but is also found
in areas that periodically experience drought conditions. In the Great
Plains states, green ash is described on floodplains, streambanks, lake
margins, and ravines but is also typical on homesteads and in shelterbelt
and windbreak plantings. Moist to wet habitats are typical green ash
habitats described for the southeastern United States as well.
Green ash tolerates a variety of soil types. Fertile, clay, silt, and/or loam
soils that range from poorly to well drained are the most common generic
descriptions of green ash soils.
The wide range occupied by green ash implies a wide tolerance of
climatic conditions. Green ash grows in humid to subhumid environ-
ments with average annual precipitation levels between 15 and 59.8
inches (380- 1,520 mm), low average January temperatures of -0.4 to
55 °F (-18 to 13 °C), mean July temperatures from 64 to 81 °F (18-27°C),
and an average number of 120 to 280 frost-free days. Green ash survival is
consistently high in shelterbelt plantings of the northern Great Plains,
where winters can be severe. However, green ash may suffer slightly
increased winterkill with age, injury from late-spring frosts, and occasional
broken stems from drifting snow. Typically a majority of green ash trees
survive the high winds and/or ice that accompany extreme weather events.
Although overwhelmingly described as a riparian, floodplain species, green
ash can survived drought conditions.
SUCCESSIONAL STATUS: Green ash is described as a pioneering,
early successional, mid-successional, subclimax, climax, and old-growth
Green ash is often described as moderately shade tolerant. Shade tolerance,
however, decreases with increasing age of green ash trees. Trees in heavy
shading had poorly developed crowns, reduced height growth, and fewer
and smaller branches. The growth rate of trees grown in moderate shade
and full sun conditions exceeded that of trees grown in heavy shade.
Many studies indicate increased green ash growth in forest openings.
Green ash is moderately flood tolerant. This tolerance rating suggests that
green ash can develop from a seedling to a mature tree in soils that are
waterlogged approximately 50% of the time. Winter, spring, and/or early
summer flooding are most typical in green ash habitats.
SEASONAL DEVELOPMENT: Green ash produces flowers before
leaves. The process from the start of inflorescence bud growth to fruit set
takes 3 years for green ash trees, and on average 1/3rd of the flower buds
initiated produce flowers. Male trees flower almost every year, while
female trees flower every 2 to 5 years. Green ash bud swell coincides
with flowering but occurs only after temperatures have reached 70 °F
(20 °C) or more.
GENERAL DISTRIBUTION: Green ash is widely distributed in the
United States and Canada. Its native range extends from Nova Scotia
west to southeastern Alberta and south through central Montana to
southeastern Texas, Florida, and the east coast. Green ash is nonnative
in Utah and Colorado, where it has escaped as an ornamental and colonized.
SKY MEADOWS DISTRIBUTION:
Tree specimens can be found on trails marked in red.
Appalachian Trail/Old Trail
South Ridge/North Ridge
Rolling Meadows/ Lost Mountain
HABITAT TYPES AND PLANT COMMUNITIES: The hardwood
forests of Virginia's lower Coastal Plain characteristically include green
ash, American elm, red maple, cherrybark oak, swamp chestnut oak,
willow oak, and/or laurel oak.
IMPORTANCE AND USES: Green ash trees and habitats provide
food and/or cover for game (e.g., wood ducks, grouse, northern bobwhites,
and wild turkeys) and nongame birds (e.g., blackbirds, finches, grosbeaks,
and cardinals feed on ash fruits), American beavers, other small mammals,
deer, bison, livestock, insects, and aquatic species. The riparian habitat in
Nebraska's Scotts Bluff National Monument, dominated by eastern
cottonwood, willow, boxelder, American elm, and green ash, occupied just
4% of the area but was habitat for 57% of the total vertebrate species
(amphibians, reptiles, mammals, and birds) surveyed. However, the
number of wildlife species supported by green ash habitats may change
with condition of the habitat. One researcher found that the green ash/
chokecherry habitat type in an early seral stage supported approximately
half the number of birds, and fewer small mammals, compared to a later
seral stage. Other research indicates that deer utilize green ash habitats
extensively, but that browsing of green ash may be limited. Ash trees are
hosts for tiger swallowtails, ash and waved sphinxes, and polyphemus
Extensive livestock use of green ash habitats likely does more damage
than browsing. Many have highlighted the use or overuse of green ash/
chokecherry habitats by livestock in the northern Great Plains. Green
ash habitats provide shade, palatable forage, water sources, protection
from severe weather, and shelter during the calving season. Livestock
also utilize green ash habitats to avoid insects, especially horn flies in the
northern Great Plains, and trees are often used as rubbing posts to remove
insect pests. Not surprisingly, the same habitat qualities attractive to
livestock are attractive to wildlife in the area. The potential for livestock/
wildlife management conflicts is considerable.
Green ash is widely used in revegetation, reclamation, and protection
plantings. Green ash commonly invades and is often actively planted on
old fields. The use of green ash in shelterbelts or other protective plantings
Green ash wood is course grained, heavy, hard, and strong. Sapwood is
white. Green ash is used to make tool handles, furniture, and interior
Green ash's salt and pollution tolerances make it a likely choice in urban
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