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• Toxicodendron rydbergii

Toxicodendron rydbergii — western poison-ivy

Facts

Western poison ivy (or poison oak) is a close relative of the more familiar poison ivy that occurs across more eastern portions of North America. Unlike its cousin, however, it grows as a small shrub and does not exhibit a viny form. It spreads by rhizomes and can form dense carpets in some areas. Although all parts of the plant are irritating to humans, wildlife and birds can sparingly browse them.

Habitat

Anthropogenic (man-made or disturbed habitats), cliffs, balds, or ledges, forests, talus and rocky slopes

Characteristics

• Buds or leaf scars

  Bud position relative to scar

  the winter bud has a leaf scar just below it

  Bud scale number

  there are no scales on the winter buds

  Bud scar shape (Fraxinus)

  NA

  Collateral buds

  there are no collateral buds on the sides of the branches

  Leaf scar arrangement

  there is one leaf scar per node on the stem or twig

  Superposed buds

  there are no superposed buds on the branch

  Winter bud distribution

  the winter buds are clustered near the tip of the twig

  Winter bud scale hairs

  NA

  Winter bud scales

  the winter bud is naked (not covered with scales)

  Winter bud stalks

  • the winter buds have no stalks
  • the winter buds have short stalks

• Flowers

  Anther color

  the anthers show no hint of a pink, reddish or purplish tint

  Carpels fused

  the carpels are fused to one another

  Enlarged sterile flowers

  there are no enlarged sterile flowers on the plant

  Flower petal color

  yellow or green

  Flower symmetry

  there are two or more ways to evenly divide the flower (the flower is radially symmetrical)

  Hairs on ovary (Amelanchier)

  NA

  Hypanthium present

  the flower does not have a hypanthium

  Inflorescence type

  the inflorescence is a panicle (branched with the individual flowers on stalks)

  Number of pistils

  1

  Ovary position

  the ovary is above the point of petal and/or sepal attachment

  Petal and sepal arrangement

  the flower includes two cycles of petal- or sepal-like structures

  Petal appearance

  the petals are thin and delicate, and pigmented (colored other than green or brown)

  Petal fusion

  the perianth parts are separate

  Sepal appearance

  the sepals resemble leaves in color and texture

  Sepal cilia (Ilex)

  NA

  Sepal tip glands

  there are no glands at the tips of the sepal lobes

  Sepals fused only to sepals

  the sepals are fused to each other (not other flower parts), at least near their bases

  Stamen number

  5

  Stamens fused

  the stamens are not fused to one another

• Fruits or seeds

  Berry color

  • some other color
  • white
  • yellow

  Fruit tissue origin

  there are no flower parts that form part of the fruit

  Fruit type (general)

  the fruit is fleshy

  Fruit type (specific)

  the fruit is a drupe (fleshy, with a firm inner ovary wall that encloses a single seed)

  Nut with spines (Fagaceae)

  NA

  Wings on fruit

  there are no wings on the fruit

• Glands or sap

  Sap color

  the sap is clear and watery

  Stalked glands on fruit (Rosa)

  NA

• Growth form

  Growth form

  the plant is a shrub (i.e., a woody plant with several stems growing from the base)

• Leaves

  Hairs on underside of leaf blade

  • the underside of the leaf has hairs on it
  • the underside of the leaf has no hairs

  Hairs on upper side of leaf blade

  • the upper side of the leaf is fuzzy or hairy
  • the upper side of the leaf is not hairy, or has very few hairs

  Leaf blade base shape

  • the base of the leaf blade is cuneate (wedge-shaped, tapers to the base with relatively straight, converging edges), or narrow
  • the base of the leaf blade is rounded
  • the base of the leaf blade is truncate (ends abruptly in a more or less straight line as though cut off)

  Leaf blade base symmetry

  the leaf blade base is symmetrical

  Leaf blade bloom

  the underside of the leaf has no noticeable bloom

  Leaf blade edges

  • the edge of the leaf blade has lobes, or it has both teeth and lobes
  • the edge of the leaf blade has teeth

  Leaf blade edges (Acer)

  NA

  Leaf blade flatness

  the leaf is flat (planar) at the edges

  Leaf blade hairs

  the hairs on the leaf blade are different from the choices given

  Leaf blade scales

  there are no scales on the leaf blades

  Leaf blade shape

  • the leaf blade is orbicular (roughly circular, as wide as long)
  • the leaf blade is ovate (widest below the middle and broadly tapering at both ends)
  • the leaf blade is rhombic (roughly diamond-shaped)

  Leaf blade texture

  • the leaf blade is coriaceous (has a firm, leathery texture)
  • the leaf blade is membranaceous (thin, flexible, almost translucent)

  Leaf blade translucent dots

  there are no translucent dots on the leaf blade

  Leaf blade vein pattern

  the main veins of the leaf blade are pinnate (the secondary veins branch off at intervals from the main central vein) and non-arcuate (not arched towards the leaf tip)

  Leaf blade veins

  the leaf blade has one main vein running from the base toward the tip

  Leaf duration

  the leaves drop off in winter (or they wither but persist on the plant)

  Leaf form

  the plant is broad-leaved (with broadly flattened leaf blades)

  Leaf lobe tips (Quercus)

  NA

  Leaf midrib glands

  the midrib of the leaf blade lacks glands on the upper surface

  Leaf stalk

  the leaves have leaf stalks

  Leaf stalk attachment to leaf

  the petiole attaches at the basal margin of the leaf blade

  Leaf stalk nectaries

  there are no nectaries on the leaf stalk

  Leaf stalk shape

  the leaf stalk is not flattened

  Leaf teeth

  • the leaf blade margin is serrate (with forward-pointing) or dentate (with outward-pointing) with medium-sized to coarse teeth
  • the leaf blade margin is undulate (wavy), but does not have teeth

  Leaf teeth hairs (Carya)

  NA

  Leaf type

  the leaf blade is compound (i.e., made up of two or more discrete leaflets

  Leaves per node

  there is one leaf per node along the stem

  Specific leaf type

  the leaf is compound, with three leaflets

  Stipules

  there are no stipules on the plant, or they fall off as the leaf expands

• Place

  Habitat

  terrestrial

  New England state

  • Connecticut
  • Maine
  • Massachusetts
  • New Hampshire
  • Rhode Island
  • Vermont

  Specific habitat

  • cliffs, balds, or ledges
  • forests
  • man-made or disturbed habitats
  • talus or rocky slopes

• Scent

  Plant odor

  the plant does not have much of an odor, or it has an unpleasant or repellant odor

• Stem, shoot, branch

  Aerial roots

  the plant has no aerial roots

  Bark texture

  the bark of an adult plant is thin and smooth

  Branch brittleness (willows only)

  NA

  Branch cross-section

  the branch is circular in cross-section, or it has five or more sides, so that there are no sharp angles

  First-year cane (Rubus)

  NA

  Lenticels on twigs

  there are no lenticels on the twigs, or they are very hard to see

  Twig papillae (Vaccinium species only)

  NA

  Twig scales

  there are no scales on the twig surface

  Twig winter color

  • brown
  • gray

  Wings on branch

  the branch does not have wings on it

  armature on plant

  the plant does not have spines, prickles, or thorns

Wetland status

Occurs in wetlands or non-wetlands. (Wetland indicator code: FAC)

New England distribution and conservation status

From the dichotomous key of Flora Novae Angliae