BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Toxicodendron diversilobum | Poison-Oak 



GENERAL BOTANICAL CHARACTERISTICS : 
Poison-oak is a many-stemmed, deciduous, native shrub or woody vine.
Shrubs are erect with stems from 2 to 6 feet (1-2 m) tall.  Vine stems
commonly reach 10 to 30 feet (3-10 m), but may be as long as 100 feet
(30 m) [22].  As a vine, poison-oak climbs trees or other support by
adventitious roots and/or wedging stems within grooves or crevices of
the support [7,22,62].  The bright green leaves have three (sometimes
five) round to ovate, diversely lobed or toothed leaflets that usually
resemble oak leaves [45,62].  Small flowers occur in leaf axils, with
male and female flowers on separate plants [38,53].  The fruits are
white drupes [45].  Rhizomes are at or just below the soil surface, and
are extensive [46].


RAUNKIAER LIFE FORM : 
   Phanerophyte
   Hemicryptophyte


REGENERATION PROCESSES : 
Poison-oak reproduces vegetatively by sprouting from the rhizomes and
root crown after disturbance such as fire or browsing has removed
topgrowth [15,44,53].  It also reproduces by layering when vine stems
contact the ground [46].

Poison-oak seeds are dispersed by birds [53].  Seedlings occur both
before and after fire, suggesting that the seeds do not depend upon fire
for scarification.  The seeds have a gummy seedcoat which leaches off
very slowly, resulting in delayed germination [37].

Poison-oak is propagated by stem cuttings [23].


SITE CHARACTERISTICS : 
Poison-oak generally grows in acid soils, and is not limited to any
particular soil texture or drainage pattern.  It occurs on well-drained
slopes and in riparian zones [1,39,64].  It is found at elevations of
less than 5,000 feet (1,524 m) west of the Sierra Nevada, growing on all
aspects [45].  In the Siskiyou Mountains it is found at up to 4,400-foot
(1,340-m) elevations on steep southern exposures [66].


SUCCESSIONAL STATUS : 
Facultative Seral Species

Poison-oak is a somewhat shade-tolerant species commonly occurring in
seral woodland and mixed evergreen forest understories [51,56].  It is
considered a climax species on south-slope Douglas-fir forests of the
Willamatte Valley foothills, Oregon [51].  In climax oak woodland,
poison-oak cover may reach 25 to 50 percent [17].


SEASONAL DEVELOPMENT : 
Poison-oak leaf buds open from February to March, and stems elongate
from March to April [37].  Flowering occurs from from March to
June [15].  Leaves drop from late July to early October [22],
and fruits disperse in summer and fall [37,53].

Related categories for Species: Toxicodendron diversilobum | Poison-Oak