Utricularia gibba is a perennial aquatic herb without roots. It has slender 25cm (10 in.) stems which may be floating, submerged or creeping along the substrate. The stem leaves are threadlike with hairless margins, alternate, numerous, and between 3 and 10mm (1/8 and 3/8 in.) long. They may be undivided or generally 2-parted at the base and each part may be forked again. The bladders or “traps” are 1 or 2 valve-lidded and borne on leaves that are less than 1/2mm (1/16 in.) wide – it is these structures that trap small invertebrates such as insects. This species has no winter buds. Inflorescence have 1 to 4 yellow flowers 6 to 8mm (¼ to 5/16 in.) long at the end of a 15cm (6 in.) stalk. The flowers are strongly irregular. The lower lips are broad, flat, and saddle shaped. The flower spurs are broadly coneshaped, but shorter than the lower lips. The fruit capsules are borne on erect stalks, and the seeds are winged (Douglas et al. 1999, Hickman 1993, in MDNR 2005).

Utricularia gibba is an obligate wetland species and occurs in lakes and lake edges and muddy disturbed sites in the lowland zone; in its native range in Washington, for example, it occurs from elevations of 50m to 100m (160 to 490 feet) (MDNR 2005).

Rook (2004) reports that “reproduction of bladderwort occurs sexually by seed when it flowers between June-August and insect pollinated. Asexually by turions (winter buds), the most common method is dense starch-rich leaf masses form at tips of branches in late fall, drop in the bottom and remain dormant through the long winter. Turions begin growing as spring water temperature rises, absorbing leaves to become buoyant\".

Bladderworts are carnivorous plants with complex modified underwater appendages or “sacs” that trap insects and other small animals; this provides them with excess nutrition which allows them to survive in low nutrient conditions (DOC 2005).

The introduced yellow flowering bladderwort (Utricularia gibba) has spread throughout the gum fields and dune lakes in part of northern New Zealand, threatening to compete with native bladderworts and sundews, including Utricularia dichotoma and U. delicatula, and the sundews Drosera auriculata, D. peltata and forked sundew (D. binata) (DOC 2005).