BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Fraxinus pennsylvanica | Green Ash 



GENERAL BOTANICAL CHARACTERISTICS : 
Green ash is a native, deciduous tree with a large, straight trunk and
high branches.  This dioecious tree grows up to 66 feet (20m) high with
diameters of 1 1/2 to 2 feet (46-61cm), although in the wooded draws of
the northern Great Plains it usually reaches about only 25 to 30 feet
(8-10m) in height [26,44,53,57].  The largest living green ash is in
Missouri, with a height of 106 feet (32m) and 4.4 feet (1.34m) in
diameter [53].

A flood tolerant tree, green ash has an extensive, moderately shallow
root system, which contributes to a high degree of windfirmness [53,57].
The bark is dark grey to brown with shallow furrows, and the wood is
heavy, hard, strong and yellowish with wide, white sapwood [44].  Apical
dominance is strong enough so that vigorous, uninjured, open-grown trees
have a single, straight stem until they are 15 ft (5m) or more tall.  In
slow growing, shaded specimens, reassertion of apical dominance when the
terminal bud is removed is slow.  Therefore, understory seedlings
frequently have poor stem form [57].  Leaves are opposite and
oddly-pinnate about 8 to 12 in (20-30cm) long with 5 to 9 (usually 7)
oblong-lanceolate or elliptic, serrate or entire leaflets [53].

The inconspicuous, unisexual flowers are borne over the entire outer
part of the live crown, usually beginning when trees are 3-4 in (8-10cm)
in diameter and 20 ft (6m) high [57].  Staminate flowers are dense
panicles which are green with reddish anthers; pistillate flowers are
greenish yellow in short panicles [44].  The fruit is an elongated,
winged, single-seeded samara borne in clusters [11], and large seed crops
are produced every year.

According to Wright [57], green ash is composed of three or more
ecotypes.  The population from the arid northwestern part of green ash's
range is more drought resistant than that from the moister central Great
Plains, and as compared to the Coastal Plain ecotype (Virginia, North
and South Carolina), the Northern States ecotype (Maine to Minnesota)
grows more slowly, has greener petioles, is more winter hardy, and the
leaves are less subject to damage by fall frosts.

Several insects feed on green ash trees: oyster scale; carpenter worm;
two ash saw flies; and unspecified borers particularly affect shade
trees and windbreak plantings.  Fungus, athracnose, rusts, and root rot
sometimes damage trees and wood.  Rabbits, deer and cattle may damage
unfenced plantings [57].





RAUNKIAER LIFE FORM : 
   Phanerophyte


REGENERATION PROCESSES : 
Green ash regenerates both through sexual and vegetative reproduction
often regenerating profusely from either seed or vegetatively after
disturbance [38].  Large seed crops are produced each year, and the
winged samaras are wind-dispersed, most within a few hundred feet of the
parent tree.  Some dispersal by water occurs, but the importance of
water as a long distance dispersal agent is not known [57].  Wind and
water dispersed seeds drop during the fall and winter months and
germinate the following spring on a variety of ground types including
moist litter as well as mineral soil, but rarely in dense vegetation
[3].  This species grows best in partial shade [38].  Plants will
reproduce from wind blown seeds along river banks [53].

This tree responds quickly to damage by sprouting when the top is
removed, especially when trees are in smaller diameter classes [3].  The
ability to sprout decreases with age and diameter of the parent tree
[25].  The plants will sprout readily from the root crown or from stumps
following damage [3,25,38,53,57], and it has been suggested that success
and propagation of this species in an island environment is more due to
its ability to sprout and resprout than to the number of successful
instances of seedling establishment [3].  Land managers can take
advantage of this reproductive strategy in northern Great Plains
declining green ash communities by using selective cutting to help
regenerate the woodlands through resprouting [25].

Green ash of sapling or pole size sprouts readily, resulting in clumps
of several stems, and cuttings made from young trees root easily under
greenhouse conditions.  However no practical way to root cuttings from
older trees has been found. This species can also be bench or field
grafted [57].




SITE CHARACTERISTICS : 
Green ash, the most widely distributed of all the American ashes, grows
in a subhumid to humid climate with an average annual precipitation of
15 to 60 inches (38-155cm) and an average length frost free season from
120 to 280 days.

This flood tolerant species is almost completely confined to bottomland
sites, but grows well when planted on moist upland soils.  It is most
commonly found on alluvial soils along rivers and brooks and less
frequently in swamps, and is common on land subject to flooding once or
twice a year, remaining healthy when flooded up to 40% of the time
during the growing season [57].  Tree species most commonly associated
with green ash are box elder (Acer negundo), red maple (Acer rubrum),
American elm (Ulmus americana), pecan (Carya illenoensis), sugarberry
(Celtis laevigata), sweetgum (Liquidambar styraciflua), American
sycamore (Platanus occidentalis), eastern cottonwood (Populus
deltoides), plains cottonwood (P. sargentii), quaking aspen (P.
tremuloides), black willow (Salix nigra), and willow oak (Quercus
phellos) [57].

In the western part of its range, mainly in the northern Great Plains,
where rainfall is insufficient to suppport upland tree growth, green ash
is commonly found in upland coulees and draws, broad valleys, and on
floodplains [9].  The tree canopy in these wooded draws is primarily
green ash, associated with American elm, boxelder, and Rocky Mountain
juniper (Juniperus scopulorum).  Chokecherry (Prunus virginiana)
dominates the sapling layer, and with snowberry (Symphoricarpos
occidentalis), makes up the shrub component.

Green ash occurs on a wide variety of soils although it survives best on
deep, permeable, well-drained loams [52], preferring these to river sand
[54].  This species has been planted on medium to coarse-textured upland
sands and loams with good moisture relations, and is tolerant of
moderately strong acid (pH 4.0) to moderately basic reacting soils [53].

The elevational ranges for green ash in several northern Great Plains
states are as follows [18,32]:

Colorado           3,500 to 5,700 feet (1,067-1,737m)
Montana            3,400 to 4,500 feet (1,036-1,372m) 
Nebraska           2,600 to 4,500 feet (793-1,372m)
North Dakota       2,240 to 3,840 feet (683-1,170m)
South Dakota       3,000 to 4,200 feet (915-1,280m)
Wyoming            4,100 to 4,400 feet (1,250-1,341m)



SUCCESSIONAL STATUS : 
Green ash is rated as intolerant to moderately tolerant of shade.  In
all but the northwestern extension of its range (northern Great Plains)
it establishes early in succession on alluvial soils either as a pioneer
or following eastern cottonwood (Populus deltoides var. deltiodes),
quaking aspen (P. tremuloides), or willow (Salix spp.).  Green ash is
less able to maintain a position in the crown canopy than its more
rapidly growing associates such as red maple (Acer rubrum) and American
elm (Ulmus americana); for this reason the proportion of ash usually
decreases with increasing age in mixed elm-ash-maple stands [57].
However the northern Great Plains is beyond the range of red maple, and
dutch elm disease has limited the expansion of American elm, therefore
it apears that green ash is the climax species in these northern Great
Plains green ash communities.  Evidence also exists that it is replacing
eastern cottonwood as the tree canopy dominant in floodplain communities
where flooding no longer occurs [23].




SEASONAL DEVELOPMENT : 
Green ash, a dioecious tree, flowers before the leaf buds start to
enlarge in March to April in Florida, and in late April to early May in
Pennsylvania.  Male flower buds require 1 to 2 weeks to pass from the
unenlarged winter condition to completion of pollen shedding which takes
about three days.  Pollen is wind disseminated, most falling within 200
to 300 feet (60-90m) of the source.  Female trees begin flower bud
enlargement a few days later, and the stigmas are receptive as soon as
they emerge from the bud for about a week.  Within one month of
pollination samaras developing from fertilized flowers reach mature
size, although growth and ripening of the embryos is not completed until
late September or early October.  Seeds begin to fall as soon as they
ripen until winter or early spring, and leaves fall at about the same
time as when the seeds ripen [57].

Related categories for Species: Fraxinus pennsylvanica | Green Ash