BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Rhus trilobata | Skunkbush Sumac 



GENERAL BOTANICAL CHARACTERISTICS : 
Skunkbush sumac is a native, perennial, cool-season shrub which grows 2
to 8 feet (0.5-2.5 m) in height [40].  Height as well as growth form
varies by geographic location:  skunkbush sumac is more branched and
compact in the Southwest and taller in the north [17].  The growth form
of this thicket-forming shrub [39] may be rounded, moundlike, or upright
[21,42].  Crown diameter is often greater than the height of the plant
and may reach up to 30 feet (9.2 m) [35,42].  Many ecotypes are known to
occur.  Varieties are distinguished by morphological characteristics
such as growth form, height, leaf shape and size, fruit shape and
pubescence.

Branches are alternate and have been described as "ill-scented" [40].
Fine slender stems spread from the woody branches [44].  The compound,
alternate leaves are green above but pale below and are unpleasantly
aromatic when crushed [40].  Leaflets grow in groups of three and are
waxy, and soft-textured [21,42].  The leaves turn a bright red or orange
in the fall.

Numerous small, yellowish-green to cream-colored flowers are borne on
spikelike panicles near the tips of branches [21,40].  The fruit is a
small, red or reddish-orange drupe containing a single nutlet [6,40,44].
The fruit is highly acidic [1].  Honeybees and other insects promote
cross-pollination of sumac flowers [5].

Skunkbush sumac has a moderate growth rate [34]; growth is most rapid
during the first 3 to 5 years [27].  Growth rates are strongly
influenced by soils and other site characteristics.  Longevity of this
species is not known; healthy rhizomes have been aged at more than 30
years [38].  Windbreak plantings have remained healthy and vigorous for
more than 20 years.

The roots of skunkbush sumac are deep and extensively branched.  The
woody rhizomes are shallow and spreading [44].  Rhizomes may extend
underground connecting shrubs more than 30 feet (9.2 m) apart [38].


RAUNKIAER LIFE FORM : 
   Phanerophyte


REGENERATION PROCESSES : 
Sexual:  Skunkbush sumac produces some seed nearly every year [6].  The
number of flowers that produce fruit is relatively low.  It was
estimated that only 5 to 15 percent of skunkbush sumac flowers in a
North Dakota shrub community actually produced fruit [38].  In this
study, the successful flower-to-fruit ratio ranged from 0 to 27.4
percent, with branches from 6 to 10 years of age producing the most
viable fruit [38].  Similar documetation for other areas is lacking.

Germination of skunkbush sumac seed is variable.  Many researchers
report poor or erratic germination [5,27,29], while others report fairly
good results [35,39,42].  Ecotypic variability probably accounts for at
least some of the differences in germination response noted.

Seeds are usually dispersed by birds and mammals.  Roadside
establishment is frequently attributable to germination of seed in
caches of mice and squirrels [42].

Vegetative:  Skunkbush sumac has spreading woody rhizomes and sprouts
readily from both the root and crown after disturbance [44].


SITE CHARACTERISTICS : 
Skunkbush sumac occurs in a variety of habitats including dry rocky
slopes, along streams and canyon bottoms, waste places, pastures,
roadsides, and on sand dunes [30,40].  It also grows as a secondary
species in plains sandhills where it often forms dense thickets [44].
Var. arenaria grows primarily on sand dunes of the Great Lakes region
[1].

Skunkbush sumac is drought resistant; it is intolerant of flooding and
high water tables [44].  It typically grows where maximum annual
precipitation ranges from 10 to 20 inches (254-510 mm) [44].  Skunkbush
sumac grows well in sun or partial shade [43,44].

Skunkbush sumac is tolerant of a wide range of soils from nearly bare
rock to sand and heavy clay [24].  It grows well on medium to coarsely
textured, moist to dry, acidic to slightly alkaline soils [24,34,43].
Skunkbush sumac can continue to grow even when partially covered by sand
or when roots are exposed by wind.  Growth is optimal in fairly deep
soil [43].  Skunkbush sumac grows well on depleted soils [39].

Elevational ranges are as follows [12]:

        from 4,500 to 7,000 feet (1,373-2,135 m) in Arizona
             3,500 to 9,000 feet (1,068-2,745 m) in Colorado
             1,900 to 4,800 feet (580-1,464 m) in Montana
             1,900 to 7,200 feet (580-2,196 m) in Utah
             4,400 to 7,700 feet (1,342-2,349 m) in Wyoming

Skunkbush sumac grows well in the mountain-brush and pinyon-juniper
zones, and in the central grassland and Rocky Mountain chaparral [35].
In streambottoms, sumac commonly grows in association with alders (Alnus
spp.), serviceberries (Amelanchier spp.), and chokecherries (Prunus
spp.)  [39].  Common plant associates in pinyon-juniper woodlands
include pinyon (Pinus edulis), Utah juniper (Juniperus osteosperma),
rubber rabbitbrush (Chrysothamnus nauseosus), broom snakeweed
(Gutierrezia sarothrae), Gambel oak (Quercus gambelii), blue grama
(Bouteloua gracilis), and galleta (Hilaria jamesii) [45].  Skunkbush
sumac also occurs with the mountain-mahoganies (Cercocarpus spp.), big
sagebrush (Artemisia tridentata), silver sagebrush (A. cana),
buffaloberries (Shepherdia spp.), shrubby cinquefoil (Potentilla
fruticosa), and many perennial grasses [44].  Skunkbush sumac sometimes
grows in nearly pure stands [39].



SUCCESSIONAL STATUS : 
Skunkbush sumac is a climax indicator in a number of shrub and grassland
communities.  It readily sprouts after fire or other disturbance and is
also a prominent species in many early seral communities.


SEASONAL DEVELOPMENT : 
In many areas, annual growth of skunkbush sumac begins in April or May.
Growth begins in May in the North Dakota Badlands, slows during April,
and is completed by early July [38].  Flowers of skunkbush sumac develop
early in the spring prior to leaf emergence [21].  Fruit generally
ripens from August to October [39].  In Utah, berries mature from June
20 to October 10 [35].  Fruit persists throughout the winter [39,40].
Leaves generally fall after the first frost [9].

Related categories for Species: Rhus trilobata | Skunkbush Sumac