Perennial aquatic or semi-aquatic herb Stem: highly variable, rooting in mud and freely branching or elongating in deeper water. Leaves: alternate and whorled on same plant, pinnately divided, with submersed leaves having three to five pairs of divisions. Emersed leaves are 0.5 - 3 cm long, linear to lance-shaped, and have comb-like divisions or sharp teeth. Flowers: either male or female, found on the same plant (monoecious), some bisexual, borne in a terminal spike above the water surface, with male flowers near the inflorescence tip. Bracts are longer than male flowers, triangular, with six to ten 1 - 2 mm long teeth that are angled toward the tip. Flowers green to purplish, small, four-parted, with 1.5 - 2 mm long petals that are rounded above and narrow-clawed. Fruit: a deeply four-lobed nut-like cluster, pale, 1.3 - 2 mm long, egg-shaped to cubic, splitting into four one-seeded segments that are flat-sided with two spiked ridges. Winter buds: absent.

Similar species: Myriophyllum pinnatum is easy to distinguish from the other Myriophyllum species by having both alternate and whorled leaves, while the other species have only whorled leaves.

Flowering: July

Habitat and ecology: Rare in our region, growing in shallow water of ditches and ponds.

Occurence in the Chicago region: native

Etymology: Myriophyllum comes from the Greek words, myrios, meaning many, and phyllon, meaning leaf, referring to its highly divided leaves. Pinnatum means feather-like.

Author: The Morton Arboretum

Lvs partly or largely alternate or scattered, 1-3 cm, with capillary segments; emersed lvs sometimes developing and resembling the bracts, these chiefly whorled, much exceeding the fls, to 18 mm, with a flat rachis to 1 mm wide and on each side 3-5 ascending teeth 1-2 mm; spikes emersed; fr 2 mm, deeply lobed, each mericarp bearing a flat or concave longitudinal ridge with sharply tuberculate margins. Mass. to O., Io., and S.D., s. to Ga. and Tex., more abundant southward. (M. scabratum)

Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.

©The New York Botanical Garden. All rights reserved. Used by permission.

From Flora of Indiana (1940) by Charles C. Deam

Our only recent report for this species is from Jasper County where I found it in the old channel of the Kankakee River half a mile west of the Tefft Bridge. It is doubtless very rare in Indiana.

……

Indiana Coefficient of Conservatism: C = 10

Wetland Indicator Status:  OBL