Why Is It a Noxious Weed?
How would I identify it?
Swollen bladderwort is a free-floating carnivorous plant. It has long, branched underwater stems and delicate, finely divided leaf-like stem branches. Yellow flowers are snapdragon-like and are emergent on upright stalks suspended by a spoked float. Like native bladderwort species, swollen bladderwort uses ovoid traps, or “bladders,” on its finely divided stems to capture small organisms.
Swollen bladderwort flowers from May to September in the Pacific Northwest. Flowers are bright yellow, to 20 mm (3/4 inch) across, and in clusters of 3 to 14 on upright stalks. The flower stalk is supported by a whorl of 5-10 spongy floating spokes measuring 3-10 cm (1 to 4 inch) long with fine divisions at the tips. The main submersed leafy part of the plant will sometimes break off from the flowering portion below the whorl of floats.
Bladderworts don’t have true leaves, instead they have alternate, highly branched, divided, leaf-like stems. Length of the overall branched structure ranges from 2-10 cm (3/4 to 4 in). The bladder-like traps are abundant on the branches, ovoid, stalked, and occur in two sizes of 0.7-1 mm (1/32 in) or 1.5-2 (3) mm (to 1/8 in).
Fruit Seed Description
Seed capsules are 3-6 mm (1/8-1/4 inch) across and globose with a thick, fleshy wall. Seeds are rough and globose with a diameter of ~0.75 mm.
May Be Confused With
Native species of bladderwort (Utricularia) can be viewed in the UW Herbarium's image database.
Where does it grow?
Swollen bladderwort occurs in ponds, lakes, swamps, and ditches, in shallow to deep water. In Washington, this species was first found in 1980 in Horseshoe Lake (Kitsap County). It is presently known in Kitsap, Mason, Thurston, Pierce, and Cowlitz counties.
How Does it Reproduce?
Swollen bladderwort reproduces by seed and can also reproduce asexually through fragmentation of the vegetative portion of the plant.
For More Information
Whatcom County NWCB Fact Sheet on swollen bladderwort