Persicaria sagittata (L.) H. Gross

Arrow-Leaved Tearthumb

Persicaria sagittata plant

Family - Polygonaceae

Habit - Taprooted annual forb, sometimes rooting at lower nodes.

Stem - Ascending, spreading, or climbing, to 2 m, glabrous but armed with small, downwardly hooked prickles. Ocreae mostly persistent, 5-13 mm long, cylindric, tan or brownish, papery, unarmed at the base, the margin entire or with erect bristles 0.2-1.0 mm, the surface glabrous.

Persicaria_sagittata_stem.jpgStem and ocrea.

Leaves - Petioles 0.5-4.0 cm long. Leaf blades 2.0-8.5 cm long, 1-3 cm wide, broadly oblong-lanceolate to arrowhead-shaped, cordate or auriculate at the base, tapered to a pointed tip, the margins otherwise entire, but sometimes hairy, the surfaces glabrous or moderately to densely appressed-hairy, the undersurface sometimes also minutely prickly along the main veins, lacking a reddish or purplish area on the upper surface.

Persicaria_sagittata_leaf1.jpgLeaf adaxial.

Persicaria_sagittata_leaf2.jpgLeaf abaxial.

Inflorescences - Terminal and axillary, solitary or grouped into small panicles, 0.5-1.5 cm long, 4-12 mm wide, dense and headlike, uninterrupted, the stalk 1-8 cm long, usually glabrous, occasionally prickly toward the base. Ocreolae usually overlapping, the margins smooth, not gland-dotted. Flowers 2 or 3 per fascicle.

Persicaria_sagittata_inflorescence.jpgInflorescence.

Flowers - Perianth white or greenish white, sometimes pinkish-tinged, bell-shaped, not gland-dotted, the tepals 5, 3-5 mm long, fused below the midpoint, the nerves not prominent, not anchor-shaped. Stamens 8, not exserted, the anthers pink. Styles 3-branched above the midpoint, not exserted, not persistent.

Persicaria_sagittata_flowers.jpgFlowers.

Fruits - Achenes 2.5-4.0 mm long, 1.8-2.5 mm wide, not exserted, 3-angled, beakless, the faces flat or slightly concave, the surfaces smooth or minutely pitted, brown to black, shiny or dull.

Flowering - June - October.

Habitat - Bottomlands, swamps, sloughs, fens, pond margins, moist swales, ditches.

Origin - Native to the U.S.

Lookalikes - Persicaria arifolia.

Other info. - This easily recognized plant has been collected from about 40% of Missouri counties, predominantly in the eastern half of the state. Its U.S. distribution includes most of the eastern half of the country, with a few scattered disjunct populations farther west.

This and one other Missouri species (P. arifolia) are often segregated into section Echinocaulon, the tearthumbs, which are characterized by curved prickles on the stems and leaves. The reason for the common name is obvious, and walking through a patch of the plants with bare legs is ill-advised. Identification is easy even vegetatively, with only P. arifolia having a similar appearance. The leaves are different in that species, having spreading, pointed basal lobes (halberd-shaped). Prickly stems are also a characteristic of Japanese hops (Humulus japonicus), but the leaves and inflorescences of that species are entirely different.

A synonym for this species is Tracaulon sagittatum.

Photographs taken at Young Conservation Area, Jefferson County, MO, 8-30-2016 (SRTurner).



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