Laportea canadensis (L.) Wedd.

Wood Nettle


CC = 4
CW = -3
MOC = 54

© SRTurner

Family - Urticaceae

Habit - Monoecious, rhizomatous perennial forb, with fibrous and sometimes tuberous roots. Plant armed with long, stinging hairs, also with sparse to dense, shorter, finer, nonstinging hairs.

Stem - Strongly ascending to erect, to 1.5 m, usually unbranched, often slightly zigzag, armed with stinging hairs.

Laportea_canadensis_stem.jpg Stem and stinging hairs.

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Laportea_canadensis_stem2.jpg Stem and node.

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Leaves - Alternate, simple, long-petiolate, stipulate. Blades 6-20 cm long, ovate to broadly ovate, broadly angled to shallowly cordate at the base, short-tapered at the tip, typically armed with stinging hairs especially on the midveins, the margins coarsely toothed, the venation pinnate or the 2 most basal lateral veins slightly more developed than the others; cystoliths rounded.

Laportea_canadensis_leaves.jpg Leaves.

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Laportea_canadensis_leaf2.jpg Leaf abaxial.

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Inflorescences - Axillary (staminate) and often appearing terminal (pistillate), paniculate clusters, the staminate panicles usually shorter-stalked than the subtending petiole and positioned at nodes below the pistillate ones, which usually are longer than the subtending petiole. Bractlets absent.

Laportea_canadensis_inflorescence1.jpg Inflorescence (staminate).

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Laportea_canadensis_inflorescence2.jpg Inflorescence (pistillate).

© SRTurner

Flowers - Minute, actinomorphic, hypogynous, mostly imperfect. Staminate flowers usually short-stalked, with 5 sepals, these 0.8-1.1 mm long, cupped around the stamens. Pistillate flowers sessile or short-stalked, the calyx consisting of 2 smaller sepals, these 0.2-0.3 mm long, spreading, alternating with 2 larger sepals, these 0.8-1.1 mm long, loosely cupped around but not fused to the ovary and fruit. Corollas absent. Stamens 5, free, opposite the sepals, the filaments bent inward in the bud, reflexing suddenly as the bud opens and ejecting the pollen explosively, the anthers attached basally, yellow, dehiscing by longitudinal slits. Pistil 1 per flower (reduced to a small peglike structure in staminate flowers), of 1 carpel, the ovary superior, 1-locular, with 1 ovule, the placentation basal. Style absent or 1, the stigma 1, linear or capitate.

Laportea_canadensis_flowers1.jpg Flowers (staminate).

Several open flowers flowers are present, each showing a pentagonal array of five stamens / anthers, with a vestigial and nonfunctional pistil at the center.

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Laportea_canadensis_flowers2.jpg Flowers (pistillate).

The erect hairlike structures are styles.

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Fruits - Achenes 2-3 mm long, obliquely attached at the tip of a short, winged stalk, strongly flattened, the body more or less circular in outline, greenish brown to dark brown, glabrous.

Laportea_canadensis_fruits.jpg Immature fruits.

© SRTurner

Laportea_canadensis_gall.jpg Unknown structure, possibly a gall.

© SRTurner

Flowering - May - August.

Habitat - Bottomland forests, swamps, sloughs, streambanks, moist shaded areas.

Origin - Native to the U.S.

Lookalikes - Boehmeria cylindrica, Urtica dioica, Acalypha rhomboidea, Pilea pumila.

Other info. - This plant is common across most of Missouri, less so in the northwestern regions of the state. Its North American range encompasses the eastern half of the continental U.S. and parts of Canada.

Learning to recognize this species is advisable for those who plan to do much hiking in Missouri, particularly in shaded bottomland forests where it is common. It can be distinguished from its common lookalikes by its alternate leaves and distinctive inflorescences. The alternate leaf arrangement alone will eliminate all lookalikes except for Acalypha, and that is typically a smaller plant. Under favorable conditions, Laportea canadensis can grow to be chest high.

Walking through a jungle of the plants with exposed areas of skin at foliage level is an unpleasant experience. The itching and burning which results can be intense, though it is fortunately usually short-lived. Conventional wisdom holds that rubbing leaves of Impatiens (which grows in similar habitats) on affected areas will lessen the irritation. The stinging sensation is caused by a witch's brew of chemical irritants and antigens, which are injected subcutaneously by the stinging hairs. These are hollow, extremely sharp at the tip, and with a bulbous reservoir at the base. They act as tiny but effective hypodermic syringes. They are stout enough to penetrate clothing, and most experienced hikers agree that Laportea canadensis is a more vicious plant than common stinging nettle.

This species is both edible and, when young, quite palatable. Naturally, it is cooked first.

Photographs taken at Weldon Spring Conservation Area, St. Charles County, MO, 8-1-2010, at Matson Hill County Park, St. Charles County, MO, 8-18-2015, and along the Busch Greenway / Duckett Creek, St. Charles County, MO, 9-25-2017 (SRTurner).