BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Toxicodendron radicans | Poison-Ivy 



GENERAL BOTANICAL CHARACTERISTICS : 
Poison-ivy is a native dioecious shrub, subshrub, or woody vine with
various growth forms:  dwarf, erect, decumbent, or high climbing [70].
It grows from 1.6 to 6.6 feet (0.5 to 2 m) high [70,109].  The trunk can
grow to 5.9 inches (15 cm) in diameter [70].  Adventitious roots allow
poison-ivy vines to grow to 150 feet (45.7 m) in length [22,70].
Rhizomes may be at the surface or deep in the soil [70].  Leaves are
three-foliate and deciduous [79].  Flowers are in axillary panicles.
The fruit is a dry, round drupe [109].


RAUNKIAER LIFE FORM : 
   Chamaephyte
   Geophyte
   Hemicryptophyte


REGENERATION PROCESSES : 
Poison-ivy reproduces vegetatively and sexually [70].  It sprouts from
aboveground vines, rhizomes, and root crowns [70].

Plants take 3 years from seed to reach the flowering stage [39].
Artigas and Boerner [9] found 11 plus or minus 7 seeds per square foot
(116.8 plus or minus 75.2 germinable seeds/sq. m) in mineral soil to a
depth of 4 inches (10 cm) in a 20- to 60-year-old white and red pine
(Pinus strobus and P. resinosa) plantation.

Seeds have an oily covering and are primarily dispersed by animals
[79,88].  Since the covering is buoyant, the fruit is also dispersed by
waterways [79].  Poison-ivy seeds that had passed through sharp-tailed
grouse digestive tracts gave good to excellent germination after both
warm (86 degrees Fahrenheit [30 deg C]) and cold (68 degrees Fahrenheit
[20 deg C]) stratification [64].  Seeds regurgitated by a crow exhibited
90 percent germination [79].


SITE CHARACTERISTICS : 
Poison-ivy grows in semiarid to humid regions [51,118,122].  One
exception is maritime areas where it grows in a perhumid climate with
localized fog [81,91].  Climate is typically continental, with short,
warm to hot summers and long, cold to cool winters [51,62].  Average
growing season ranges from about 150 days at its northern limit in
Quebec to 240 days in the south in Florida [54,62].  Minimum temperature
averages 41.6 degrees Fahrenheit (5.3 deg C) in the north and a maximum
average of 66.2 degrees Fahrenheit (19 deg C) in the west [54,128].

Annual precipitation averages from a minimum of 15.4 inches (391 mm) in
the northern part of its range and 18.3 inches (465 mm) in the western
part to a maximum of 57 inches (1,450 mm) at the southern limit
[35,48,51].  Snowfall averages between 12 and 74 inches (30.5-188 cm)
over most of its range [51].

Poison-ivy occurs in a large variety of soil conditions.  Soil textures
may be poorly drained clays with gleying and mottling present
[34,38,44,98].  Soils also may be well-drained silty loams to loamy
sands [46,81,105,116,122].  Under loblolly pine (Pinus taeda) on
well-drained sites, poison-ivy had an average cover of 1.4 percent;
poison-ivy cover decreased to a trace in poorly drained swales of
Chinese tallowtree (Sapium sebiferum) [49].  In green ash-hickory
stands, poison-ivy seedlings were of higher importance (49.16) on silt
loam soil compared to 7.65 importance rating on silty clay soil [43].
Soil pH varies from acidic (pH 6.0) to moderately alkaline (pH 7.9)
[24,35].

Topography is flatland to rolling hills [33,56,116].  Poison-ivy also
occurs on steeper slopes in the southwestern states [71].  Upper
elevation limits for poison-ivy growth are 7,080 feet (2,158 m) in New
Mexico and 1,700 feet (518 m) in Tennessee [35,94].

Poison-ivy is found under all moisture conditions.  It was the most
widely distributed species along a moisture gradient in central Illinois
[1].  Poison-ivy occurs most frequently on moist, open sites [71,113].
However, Archambault and others [8] noted that poison-ivy was most
characteristic of dry, open sites in Michigan.

Poison-ivy is an important species in swamps and is mostly restricted to
mixed swamps in Florida, not extending into bayheads [82].  It is
tolerant of brackish or mildly saline water [12].  Poison-ivy can
survive inundation and fluctuations in water levels (e.g., in cypress
(Taxodium spp.) swamps or cabbage palmetto (Sabal palmetto) communities)
because of adventitious roots along the climbing vine [118].  Seasonally
flooded areas often are more alkaline because decaying plant material is
washed away; poision-ivy grows better in these sites [82,83].
Poison-ivy decreased in importance with an increase in flooding depth
[83].

There was no difference in poison-ivy cover between a young oxbow marsh
area (inundated at some point during the year) and a mid-age oxbow.
Poison-ivy was not present on the oldest oxbow, located above the
floodplain [53].

Poison-ivy occurs on a large variety of sites.  It is found in riparian
communities, gallery forests, open dry or wet woods, and hillsides
[100,121].  It occurs on sand dunes of lake shores and barrier islands
[10,75,92,128].  Poison-ivy roots on the bases of cypress (Taxodium
distichum) in large peat mats [23,25,83,102].  It is also found on
hammocks [4,62].

Poison-ivy is common in disturbed places, such as roadside thickets,
stone walls, fences, railroads, clearcuts, and orchards [18,59,104,111].
It also occurs in urban settings.  Poison-ivy was 1 of 10 species most
important (42.4 percent frequency) in an herbaceous layer in the Bronx,
New York [127].

Common overstory associates of poison-ivy not included in Distribution
and Occurrence are bur oak-aspen (Populus tremuloides), green ash,
American elm, Florida torrey (Torreya taxifolia), southern red oak
(Quercus falcata), and blackgum (Nyssa sylvatica) [17,73,87,107,121].
Additionally, poison-ivy occurs with sycamore (Platanus wrightii),
boxelder (Acer negundo), wax myrtle (Myrica cerifera), and redbay
(Persea borbonia) [16,25,82,92, 117].

Common understory shrub associates are skunkbush (Rhus trilobata),
snowberry (Symphoricarpos occidentalis), common chokecherry (Prunus
virginiana), blackberries (Rubus spp.), trumpetcreeper (Campsis
radicans), and sweet fern (Comptonia peregrina) [34,37,94,107,125,128].

Associated vines are greenbrier (Smilax spp.), grapes (Vitis spp.), and
Virginia creeper (Parthenocissus quinquefolia) [57,93]. Other species
found with poison-ivy are broomsedge bluestem (Andropogon virginicus,
heartleaf foamflower (Tiarella cordifolia), sweet spire (Itea
virginiana), brackenfern (Pteridium aquilinum), and lizardtail (Saururus
cernuus) [16,87,99,102,108,114].


SUCCESSIONAL STATUS : 
Facultative Seral Species

Poison-ivy is a common intruder into ruderal sites in North America,
while in Japan, it is a component of old growth [39].  Poison-ivy is an
early competitor with other species that may become established in the
overstory [88].  Cowles [19] classified poison-ivy as a primary dune
colonizer, establishing before the xerophytic evergreen flora [19].

Poison-ivy is somewhat shade tolerant [67].  However, it was unable to
compete with an introduced noxious species, Brazilian pepper-tree
(Schinus terebinthifolius) in Florida pineland [74].

Poison-ivy occurs in subclimax associations of oak (Quercus spp.) and
aspen in the Great Plains and in climax types of sugar maple-basswood
(Acer saccharum-Tilia grandifolia) [14,21].  In sugar
maple-basswood/prairie ecotone, poison-ivy occurred with a 3 percent
frequency [65].

Poison-ivy occurs in late seral and climax communities.  In secondary
succession of old fields, poison-ivy was present in seral stages of 30-
to 100-year-old stands (the pine stage with loblolly and shortleaf pines
[Pinus echinata]) and in 150-year-old stands (the pine-hardwood stage
with shortleaf pine, northern red oak [Quercus rubra], magnolia
[Magnolia grandiflora], and American beech [Fagus grandifolia]) [89].
In another study, poison-ivy occurred in late seral stages of
pine-hardwoods and in climax communities of magnolia and American beech
[69].  Poison-ivy was present in climax white oak (Quercus alba)-
American beech communities [91].


SEASONAL DEVELOPMENT : 
Poison-ivy flowers when the leaves are about half open [70].  It blooms
May to July throughout its range [22,40,59,110].  Fruits mature from
August through November [95,104,111].  Fruit may persist until the
flowering next season [70,79].  Leaves are dropped after freezing
temperatures in the fall.

Related categories for Species: Toxicodendron radicans | Poison-Ivy