Rhodora 23: 37. 1921.
Annuals or perennials. Stems erect or ascending, 15–60(–80) cm, glabrous or glandular-hairy distally. Leaves: petiole 0 mm; blade oblong-ovate to oblong-lanceolate, (5–)25–50(–100) × 4–15(–30) mm, 2.5–5 times as long as wide, base amplexical-truncate or amplexical-subcordate, margins entire or subentire, apex acute, surfaces glabrous. Racemes 10–25, axillary, 100–160 mm, 15–25-flowered, axis glabrous or glandular-hispid; pedicels less than 3 per cm, glabrous or scarcely to densely short glandular-hairy, rarely completely glabrous; bracts oblong, 3–5 mm, apex obtuse. Pedicels patent, (3–)5–10 mm, equal to or ± shorter than subtending bract, glabrous or glandular-hairy. Flowers: calyx lobes 2.5–3 mm, apex obtuse, glabrous or glandular-hairy; corolla white to pale pink with darker veins not reaching margins, 4–5 mm diam.; stamens 5 mm; style (1.3–)1.5–2.5 mm. Capsules ± compressed in cross section, subglobular, 2.5–3(–3.5) × 3–4 mm, apex emarginate, sinus 0.1–0.3 mm, glabrous or glandular-hairy. Seeds 26–123, yellow-brown, ellipsoid to subglobular, planoconvex, 0.4–0.7 × 0.3–0.5 mm, 0.2–0.3 mm thick, smooth. 2n = 36.
Phenology: Flowering Jun–Oct.
Habitat: Wet places, rarely running water, lakeshores, ditches, muddy places, stream channels.
Elevation: 0–2500 m.
Alta., B.C., Man., Ont., Que., Sask., Calif., Idaho, Ill., Ind., Iowa, Kans., Maine, Mass., Mich., Minn., Mo., Mont., Nebr., Nev., N.Mex., N.Y., N.Dak., Ohio, Okla., Oreg., Pa., S.Dak., Tenn., Tex., Vt., Va., Wash., W.Va., Wis., Wyo., Europe.
Veronica catenata seems to be a relative of V. anagallis-aquatica that is more cold-adapted, as seen in Europe (R. Götte 2007), and native to the flora area. Although no specimens were seen it may be found in Alaska, Connecticut, and Kentucky.