Annual herb Stem: free-floating or creeping along soil in shallow water. Bladders form on specialized branches. Leaves: many, 0.5 - 2 cm long, often three-parted at base and forking one to three times into flat and slender segments with toothed margins (10x magnification required). The segments do not become much thinner with further dissection, and the end segments are blunt-tipped. Flowers: borne two to four on a stalk (scape), yellow petals are two-lipped with lower lip twice as long as the 8 - 12 mm upper lip and having a projection in the center. The spur (extended sac at base of petals) is cylindrical and almost as long as the lower lip. Fruit: a two-valved capsule containing small seeds.
Similar species: Utricularia radiata, U. minor, U. macrorhiza, U. geminiscapa, and U. gibba are other aquatic or amphibious Utricularia species with dissected leaves. The flower stalk of U. radiata has a whorl of leaves with inflated petioles. Utricularia macrorhiza, U. geminiscapa, and U. gibba have leaf divisions that are circular in cross-section. Utricularia minor has terminal leaf divisions that are non-toothed and traps that are borne on the leaves.
Flowering: late May to early September
Habitat and ecology: Rare in shallow water of marl flats, alkaline bogs, and fens.
Occurence in the Chicago region: native
Etymology: Utricularia comes from the Latin word utriculus, meaning "a small bottle."This refers to the insect-trapping bladders on the leaves and runners of the bladderworts. Intermedia means intermediate.
Stems free-floating or creeping on the soil under shallow water; lvs numerous, mostly 0.5-2 cm, commonly 3-parted at base and then 1-3 times dichotomous, the segments slender, flat, not much narrower in successive dichotomies, the ultimate ones rather blunt; bladders on specialized branches distinct from the lvs; fls mostly 2-4 in a lax raceme on an emergent peduncle 6-20 cm; pedicels to 15 mm, remaining erect; cor yellow, the lower lip 8-12 mm, with well developed palate, nearly twice as long as the upper lip; spur nearly as long as the lower lip; 2n=44. Shallow water; circumboreal, s. to Del., Ind., and Calif. Summer.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
This species has been reported from Kosciusko and Marshall Counties by Clark, and from Lake County by Peattie and by Pepoon. In a letter from J. H. Barnhart of the New York Botanical Garden, dated June 11, 1932, he says that there are two specimens from Indiana in that herbarium. One is from Marshall County collected by Scovell & Clark near Lake Maxinkuckee, August 13, 1900. The other is one from Lagrange County, which I collected June 1, 1916. I also have it from Elkhart, Lake, La Porte, and Steuben Counties.