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General Information about Fanwort
Fanwort (Cabomba
caroliniana)
is a beautiful looking aquarium plant with
fan-shaped underwater leaves. It is native to the southeastern
United States, but is considered to be very weedy even where it is
native. It is not native to the western United States, but has
been introduced into Washington waters. Fanwort is growing in a
slough off the Columbia River in the Longview/Kelso area in
southwestern Washington and is also found in some coastal lakes in
Oregon.
Growth Habit
Fanwort grows very densely where it has been
introduced and because it has tightly-spaced leaves, it has a
tubular appearance in the water. Fanwort has been in Cullaby Lake,
on the north coast of Oregon, for at least ten years where it
creates severe nuisance conditions. Fanwort is a serious aquatic
weed as far north as upstate New York and Michigan (out of its
native range). It clearly has the ability to grow and create
serious weed problems in Washington.
Like many problem aquatic plants, fanwort can
reproduce from small fragments. Fanwort stems become brittle in
late summer, which causes the plant to break apart, facilitating
its distribution and invasion of new waterbodies. Although fanwort
produces seeds, there is no information about seed viability in
the Pacific Northwest.
Management
There has been little research on fanwort
biology or management. There are reports that fanwort is less
sensitive to the herbicides available for management in
Washington, than other aquatic plants. Grass carp are known to eat
fanwort. Unlike most other rooted aquatic plants, fanwort may get
most of its important nutrients from the water rather than the
sediment. Therefore, fanwort may be sensitive to reduction of
nutrients in the water.
Identification
With its fan-shaped leaves, fanwort is
relatively easy to identify, although there are a couple of native
look-alike plants in Washington (the aquatic buttercup and the
aquatic marigold) that also have fan-shaped leaves.
Look for:
- Fan-shaped leaves on short stalks arranged in
opposite pairs.
- Underwater stems have a "tubular" appearance.
- Small (less than one-inch long), oval or
sometimes triangular floating leaves with the stem attached in
the center are sometimes present.
- The flower has white petals and floats on the
water surface.
- The plant sometimes looks reddish.
The fanwort infestation in Washington is in a
pioneering stage. Prompt action and vigilant monitoring of our
lakes, may prevent further spread and increased management costs
in the future. Because fanwort is still legally being sold as an
aquarium plant in Washington (2000), people must never discard the
contents of an aquarium into any waters.
Source: Washington State Department of
Ecology |
