Swollen Bladderwort

Utricularia inflata

Swollen Bladderwort

Family: Lentibulariaceae

Weed class: monitor list
Native to: New Jersey to Florida and westward to eastern Texas and southeastern Oklahoma
Legal listings:

This plant is also on the Washington State quarantine list. It is prohibited to transport, buy, sell, offer for sale, or distribute plants or plant parts of quarantined species into or within the state of Washington or to sell, offer for sale, or distribute seed packets of seed, flower seed blends, or wildflower mixes of quarantined species into or within the state of Washington. Please see WAC 16-752 for more information on the quarantine list. For questions about the quarantine list, contact the Washington State Department of Agriculture's Plant Services Program at (360) 902-1874 or email PlantServices@agr.wa.gov.


Why Is It a Noxious Weed?

This plant is on the monitor list - it is not a listed noxious weed in Washington. Please contact its sponsor Jenifer Parsons to report locations or for more information.

How would I identify it?

General Description

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.

Flower Description

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.

Stem description

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

WA Department of Ecology's Aquatic Plant Identification Manual information on swollen bladderwort

Invasive Plant Atlas of the United States

Flora of North America, Lentibulariaceae by Garrett E. Crow, 2015.

Whatcom County NWCB Fact Sheet on swollen bladderwort

Images from the UW Herbarium's image database.

Additional Photos