General Information About Swollen Bladderwort (Utricularia inflata)
Swollen bladderwort (Utricularia inflata) is a member of a fascinating
group of freely-floating, rootless, carnivorous aquatic plants. It is
native in the southeastern United States, but is increasingly being seen
in some western Washington lakes where it is considered to be a nuisance.
In 1998, it has been seen in many lakes in Mason, Kitsap, and Thurston Counties.
Where present, it has been known to form dense beds of floating plants.
Lake Limerick residents spend several thousand dollars harvesting this
species each summer.
Growth Habit
In Washington swollen bladderwort flowers from June to July. When flowering, the plant forms a wheel-like floating platform that supports a yellow snapdragon-like flower. These flowers stick up about six inches above the water surface. Washington's native bladderworts do not have this "floating wheel" to support their flowers, but when not flowering our native bladderwort and swollen bladderwort are very similar in appearance.
Swollen bladderwort reproduces from small fragments and
from seed. A Florida botanist reports that when plants become stranded on
mud, they can produce long threadlike branches with each
"thread" bearing a tiny tuber at its tip. When not in flower,
swollen bladderwort floats below the water's surface.
Photograph
of Utricularia spp. © by Kerry Dressler
Bladderwort obtains its nutrients from the water and from tiny creatures that it captures in its seed-like bladders. These bladders are actually traps that use a vacuum to capture small invertebrates that trigger a trap door. Once inside the bladder, enzymes are secreted to digest the prey, providing the plant with nutrients.
Management
The swollen bladderwort infestation in Washington appears to be in a pioneering stage. We do not know how these plants were introduced, nor do we have good distribution data. Because of the interesting "spoke-like" flower platform and the yellow flowers, bladderwort may have been introduced as a water garden plant or aquarium plant. It may also be popular with people who cultivate carnivorous plants.
Swollen bladderwort has been observed in isolated ponds where it is unlikely that boats visit. This plant might be spreading by waterfowl. A 1996 Sonar treatment in Lake Limerick, Mason County, appeared to control this species for about two years. Grass carp will consume swollen bladderwort, although it did not appear to be a preferred species in Silver Lake, Cowliz County, Washington. Another technique used by Lake Limerick residents is to hire school kids to rake or hand pull each plant from the lake.
Identification
Washington is also home to several native bladderwort species and these plants can be readily distinguished from other aquatic plants by the small, round, seed-like structures (bladders) that are interspersed throughout the green foliage. However, when not flowering, identifying native bladder plants from swollen bladderwort is very difficult.
Look for:
- Lacy underwater foliage with seedlike bladders
- Yellow snapdragon-like flowers
- A spoke-like structure supporting the flower stalk
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