Annual or perennial herb 3 - 20 cm tall Stem: with very delicate underground parts and 0.5 mm long bladders. Leaves: absent or linear, to 1 cm long. Flowers: of two types, fully opening (chasmogamous) and non-opening (cleistogamous). Fully opening flowers are rare, borne one to ten on a slender stalk (scape), subtended by bracts, and have yellow petals that are two-lipped with the upper lip much smaller than the 4 - 7 mm lower lip, and the lower lip having an almost spherical projection. Spur (extended sac at base of petals) about as long as and pressed against lower lip. Non-opening flowers are usually borne solitary on a slender stalk. Fruit: a two-valved capsule containing small seeds.
Similar species: Utricularia cornuta is also a terrestrial species with leaves that are linear or absent. It differs by lacking flowers that remain closed (cleistogamous) but commonly having flowers that open (chasmogamous).
Flowering: late June to late August
Habitat and ecology: In sandy soils, such as pannes and bottoms of large blowouts.
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. Subulata means awl-shaped.
Underground parts very delicate, rarely collected, with bladders 0.5 mm; aerial lvs, if present, linear, to 1 cm; flowering branches very slender, erect, 3-20 cm, 1-10-fld; bracts ovate or elliptic, 1-2 mm, peltate, attached at or below their middle; pedicels 4-15 mm; cor commonly yellow, the lower lip usually 4-7 mm, with prominent palate and widely spreading limb; spur about equaling the lip and appressed to its lower surface. Wet soil and very shallow water, often among mosses; N.S. to Fla. along the coastal plain, thence w. to Ark. and Tex. May-Sept. (Setiscapella s.) A depauperate form 2-5 cm with 1-3 whitish fls 1-2 mm sometimes occurs with the normal form. (U. cleistogama; Setiscapella c.)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.