Eastern Poison Ivy (Alternate names: Markweed, Poison Creeper)
Kingdom: Plantae, Division: Tracheophyta, Class: Magnoliopsida, Order: Sapindales, Family: Anacardiaceae, Genus: Toxicodendron, Species: Toxicodendron radicans · Anacardiaceae (Cashew or Sumac family) · Trifoliate compound leaf (consisting of three leaflets); Deciduous
Species
Toxicodendron radicans
Leaf Type
Trifoliate compound leaf (consisting of three leaflets); Deciduous
Family
Anacardiaceae (Cashew or Sumac family)
Shape
Ovate to elliptic, with the terminal leaflet having a longer petiolule and lateral leaflets being nearly sessile and often asymmetrical or mitten-shaped with crude side lobes.
Size
Individual leaflets are approximately 2-4 inches (5-10 cm) long and 1.5-3 inches wide, which falls within the typical species range of 2-6 inches long per leaflet.
Margin
Irregularly lobed, coarsely dentate, to smooth/entire; lateral leaflets commonly possess characteristic outer-edge thumbs or lobes.
Arrangement
Alternate along the stem.
Rarity
Very Common
Color & Pattern
Medium to dark green upper surface with light green undersides. Emerging spring leaves often show a reddish hue, while autumn leaves turn brilliant shades of red, orange, and yellow. The specimen shows dark brown necrotic spots (fungal or environmental leaf spots).
Venation Pattern
Pinnate venation with prominent pale midribs and primary veins branching towards the margins.
Texture & Surface
Semi-glossy to matte upper surface with fine pubescence along the leaf edges and main veins on the underside.
Description
A woody vine or low shrub notorious for causing allergic contact dermatitis. Leaves consist of three leaflets ('leaves of three, let it be'). The central leaflet has a longer stalk, while side leaflets often resemble asymmetrical mittens. Stems form hairy aerial roots when climbing trees or structures. In late spring, it produces small, yellowish-green flowers followed by waxy, cream-colored berries in autumn.
Key Features
Trifoliate arrangement with 3 leaflets; central leaflet stalked while lateral leaflets are nearly stemless; asymmetrical lateral leaflets often with 1-2 thumb-like lobes on the outer edge; lack of thorns or spines; hairy vine roots on mature climbing stems.
Habitat
Extremely adaptable; grows in open woodlands, forest edges, thickets, roadsides, disturbed areas, riverbanks, and suburban gardens. Tolerates full sun to deep shade and dry to moist soils.
Geographic Range
Native to eastern North America, spanning from Quebec south to Florida and west to Arizona and Texas, as well as parts of Mexico and China. Widely distributed and native.
Condition Notes
Fair condition. Several leaflets display localized dark necrotic leaf spots and minor insect chewing along the margins. The leaves show healthy chlorophyll production and active growth despite minor fungal or environmental spot damage.
Interesting Facts
The plant produces urushiol, an oily resin that causes severe allergic reactions in about 85% of humans. Surprisingly, birds and white-tailed deer are immune and actively feed on the berries and foliage without harm.
Medicinal & Uses
No modern internal or medicinal uses due to extreme toxicity. Historically used in homeopathy in minute diluted doses, but strongly discouraged. Value lies purely in ecological restoration and wildlife food supply.
Ecological Role
High ecological value in native ecosystems. High-protein foliage is grazed by deer, while over 60 species of birds consume the pale berries in winter when other food sources are scarce.
Similar Species
Boxelder (Acer negundo) seedlings have opposite leaves rather than alternate; Virginia Creeper (Parthenocissus quinquefolia) typically has 5 leaflets; Fragrant Sumac (Rhus aromatica) has sessile terminal leaflets and fuzzy red berries; Blackberry/Raspberry (Rubus spp.) have thorny stems.
Foraging Tips
Do NOT forage or touch. Remember the classic safety adages: 'Leaves of three, let it be', 'Longer middle stem, stay away from them', and 'Berries white, run in fright'. Always check for alternate stem attachment and absence of thorns.
Toxicity Warning
HIGHLY TOXIC / SEVERE ALLERGEN. All parts contain urushiol resin. Skin contact causes severe, itchy, blistering dermatitis that can last 1-3 weeks. Burning the plant releases toxin in smoke, which can cause severe respiratory distress.