Persicaria punctata (Elliott) Small

Water Smartweed

© SRTurner

Family - Polygonaceae

Habit - Annual or perennial forb, sometimes with rhizomes and/or stolons, the stems sometimes rooting at the lower nodes.

Stems - Ascending to erect, to 90 cm, often from a spreading base, glabrous, but gland-dotted. Ocreae persistent, usually tearing with age, 9-18 mm long, somewhat inflated toward the base, brown and papery throughout, truncate, not oblique at the tip, lacking a flange of tissue at the tip, the margin with erect bristles 2-12 mm long, the surface glabrous or sparsely hairy, gland-dotted.

	Stem and node.
© SRTurner

	Ocrea.
© SRTurner

Leaves - Alternate, simple. Petioles absent or to 1 cm long. Leaf blades 4-10 cm long, 0.6-2.0 cm wide, lanceolate to narrowly ovate or somewhat rhombic, angled or tapered at the base, angled or tapered to a sharply pointed tip, the surfaces glabrous or the undersurface minutely roughened along the midvein, unarmed, the undersurface with impressed glands (these sometimes pale), the upper surface lacking a reddish or purplish, chevron-to crescent-shaped or triangular area.

	Stem and leaves.
© SRTurner

	Leaf adaxial.
© SRTurner

	Leaf abaxial.
© SRTurner

	Leaf abaxial surface.
© SRTurner

Inflorescence - Inflorescences terminal and sometimes also axillary from the upper leaves, solitary or few per main stem, 5-20 cm long, 4-8 mm wide, erect or ascending, straight or sometimes slightly zigzag, mostly open with irregularly spaced flowers, usually interrupted, the stalk 3-6 cm long, glabrous, but gland-dotted. Ocreolae mostly not overlapping, the margins usually with short bristles 1-2 mm long, the surface gland-dotted (the dots sometimes pale).

	Inflorescence.
© SRTurner

	Ocreolae and inflorescence axis.
© SRTurner

Flowers - Perfect, mostly 2-6 per fascicle, all similar. Perianth green toward the base, white or rarely pinkish-tinged toward the tip, bell-shaped, moderately to densely dotted with scattered, minute glands (these sometimes pale and inconspicuous), the tepals 5, 3.0-3.5 mm long, fused below the midpoint, the nerves conspicuous or inconspicuous, irregularly few-branched (not anchor-shaped). Stamens 6-8, not exserted, the anthers pink or red. Styles 2-or 3-branched from near the base, not exserted, not persistent.

	Flowers.
© SRTurner

	Tepal punctations.
© SRTurner

	Open flowers.
© SRTurner

Fruits - Fruits 1.8-3.2 mm long, 1.5-2.2 mm wide, not or only slightly exserted, 3-angled or discoid, beakless, the faces concave (in 3-angled fruits) or slightly convex (in discoid fruits), lacking a central hump, the surface smooth, dark brown to nearly black, shiny.

Flowering - July - November.

Habitat - Streambanks, spring branches, pond margins, swamps, sloughs, fens, marshes, bottomland forests, crop fields, fallow fields, ditches, disturbed areas; sometimes emergent aquatics.

Origin - Native to the U.S.

Lookalikes - Other species of Persicaria, particularly P. hydropiperoides (common) and P. robustior (uncommon).

Other info. - This common species of smartweed is found in wet areas more or less across Missouri, and across much of the continental U.S. with the exception of Plains and Mountain states. Many species of Persicaria can look alike. This one has white inflorescences which are narrow, somewhat crowded but with sections of the axis usually visible between flowers, and leaves which are mostly narrower than 2 cm. Prime features for identification are the bristles atop the ocreae at stem nodes, and the punctations visible on the tepals. The latter character is indicative of the species but not unique to it, since the lookalikes listed above can also have dotted tepals. These dots should be searched for with magnification, and sometimes can be difficult to observe.

Smartweeds are among the most important food sources for marsh and aquatic wildlife. Some were also used by Native Americans, both as food and medicine.

Photographs taken at East Central College, Franklin County, MO, 9-14-2023 (SRTurner).