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Bladderwort comparison table
Bladderwort comparison table

Utricularia macrorhiza, Utricularia radiata, Utricularia purpurea, and Utricularia intermedia


common bladderwort in-situ
Common bladderwort in-situ

Habitat: Nine species of bladderwort are found in Maine. Four of these are possible invasive plant look alikes:
Common bladderwort (Utricularia macrorhiza)
Floating bladderwort (Utricularia radiata)
Large purple bladderwort (Utricularia purpurea)
Northern bladderwort, or flat-leaf bladderwort (Utricularia intermedia)

All four species are aquatic and occur in both the floating-leaved and submersed plant communities. They may be found free floating at or below the water surface, or trailing along the bottom of lakes, ponds, slow-moving streams, and wetland pools. Most aquatic bladderworts are adapted to survival on dry land when stranded by low water levels. Unlike rooted aquatic plants, that draw their nutrients primarily from the sediments, bladderworts, lacking roots, draw nutrients directly from the water. Bladderworts are carnivorous, and supplement their nutrient intake by capturing small prey, such as zooplankton or small insects.

Description: Tiny, lopsided sack-like bladders used for capturing invertebrate prey are either attached directly to the leaves or to specialized leafless stems. In addition to this key shared feature, all four bladderworts discussed here have finely-divided, branched, submersed leaves and produce irregular snapdragon-like flowers. Beyond these common characteristics, however, the four look alike bladderwort species are easily distinguishable. The chart on page 68 provides a summary of key distinguishing features.

Floating bladderwort
Floating bladderwort in flower

U.S. Range: All four species are native to Maine and found throughout much of New England and other parts of the United States.

Northern bladderwort submersed stems
Northern bladderwort submersed stems

Annual Cycle: All four species are aquatic perennials that propagate primarily from stem fragments. Flowers followed by fruits are borne at or above the surface in mid-summer, and winter buds are produced on the submersed stems toward the end of the growing season. At the end of the growing season, plants sink to the sediments and decay. The winter buds and some of the stem fragments overwinter intact. When the water warms in the spring, winter buds inflate with air and float to the surface where new growth begins.

Value to the Aquatic Community: Bladderworts offer shade, invertebrate habitat and foraging opportunities for fish. Common bladderwort and large purple bladderwort often occur in extensive, dense colonies.

Look Alikes: May be confused with other plants with finely divided leaves including fanwort, hornworts, mermaid weeds, water crowfoots, water marigold, and leafy water-milfoils.

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Northern Bladderwort floating Northern Bladderwort submersed Common Bladderwort bladders Common Bladderwort flowers Common Bladderwort stem Large Purple Bladderwort flower Large Purple Bladderwort stem Floating Bladderwort in-situ Floating Bladderwort illustration Northern Bladderwort illustration Common Bladderwort illustration Large Purple Bladderwort illustration

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