Jepson Manual (Preston and Constance 2014), McDougall 1973, Welsh et al 1987
Duration: Perennial Nativity: Native Lifeform: Forb/Herb General: Perennial herb, 5-30 cm tall, with slender creeping stolons, often growing as an emergent aquatic; herbage glabrous. Leaves: Petioles 3-20 cm long, erect and emerging directly from stolons; each petiole topped with a round, peltate leaf blade, 5-60 mm wide, with shallowly lobed or notched margins. Flowers: Tiny and greenish-white, subsessile or on short peduncles, in a few well-separated whorls around stalks that ascend directly from the stolons; stalks 1.5-20 cm long. Fruits: Capsules ovoid to ellipsoid, 1-3 mm wide, ribbed. Ecology: Found moist ground and in slow-moving or still water, below 5,000 ft (1524 m); flowers May-August. Distribution: Throughout the southern half of the US, from MA to FL and west to CA and OR. Notes: Look for this species at streamsides, pond margins, and other marshy areas. It prefers saturated soils and will grow where there is standing water. Look for the peltate leaves (the leaf stalk is attached to the center of the leaf instead of the edge) and flower stalks with a few, well-separated whorls of tiny flowers. H. ranunculoides is similar but the leaves are not peltate, and the flowers are in tiny umbels at the tips of the flower staks. Ethnobotany: Unknown, but other species in the genus have uses. Etymology: Hydrocotyle is from Greek hydor, water and kotyle, a small cup, while verticillata means whorled. Synonyms: None Editor: SBuckley 2010, AHazelton 2015
Stems filiform, creeping; lvs orbicular, peltate, to 6 cm, commonly with 8-14 shallow lobes; infl (except in depauperate plants) a simple or once to thrice forked spike to 15 cm or even more, bearing 2-several whorls of fls, these rarely more than 7 per whorl; fr 3-4 mm wide, truncate to rounded at base, the margins acute. Mass. to Fla. and Tex., chiefly near the coast; w. U.S. and trop. Amer. June-Aug. Typical H. verticillata has the fls and frs sessile or subsessile. Plants with distinctly pedicellate fls and frs, the pedicels to 1 cm, occur over the same range and have been called var. triradiata (A. Rich.) Fernald. (H. canbyi; H. australis)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.