Vegetation Identification - Floating Plants
Floating Plants account for some of the most prolific and invasive plant
species. Giant Salvinia, Water Hyacinth and Water Lettuce are three of
the most troubling Non-Native Invasive species of plants to ever be
introduced to Texas waters. There are also some Native plants that can
rapidly cover a pond, such as Duckweed and Watermeal.
Floating plants have an advantage over other plants in that they are the
first to recieve sunlight. Once a stand of vegetation is started on a
lake it can shade out everything below it and have less competetion for
nutrients. If an infestation gets to the point that it covers the entire
surface of a pond it can prevent the exchange of oxygen and lead to
serious problems for your fish.
Here you can see a lake that has atleast 20+ acres of solid Waterr
Hyacinth. This vegetation can double the size of a stand in as little as
14 days. So even if this lake took a few years to reach this level of
growth it could be completely covered in a matter of weeks. A lake in
this condition offers little recreational value.
For more information on
from the USDA
Common Floating Aquatic Plants
We've already mentioned the severity of Giant Salvinia and Water
Hyacinth, however Giant Salvinia is not extreamely common at this time.
Water Hyacinth is very common along the Gulf Coast and in regions that
are not prone to winter freezes. The Duckweeds though, are probably the
most common floating plants found in Texas. There are about 7 different
species of Duckweed and several species are often found in one location
along with Watermeal, which looks like duckweed in miniature.
Duckweeds are small, single, circular to oblong leaves that float on the
surface. At least a single root can be found hanging below each frond or
leaf and certain species will have multiple roots on a single frond.
Duckweeds and Watermeal are the smallest flowing plants on the planet.
Blooms are not visable to the naked eye.
Azolla or Mosquito Fern is another common plant in this area. At first
glance Azolla may apear to be Duckweed with a red color, but upon close
inspection you will see a leaf structure that is very different from
Duckweed. Azolla is a true Fern and it's leaves somewhat resemble that
of common ferns, under magnifiaction it may appear as multiple diamonds
Picture: Azolla, Duckweed and Watermeal under magnificaiton. The Azolla
is the largest and has a redish color along it's edges. Duckweed is the
next largest plant, green and somewhat circular. Watermeal is the
smallest. Duckweed is usually about 1/16" across the leaf.
Control of Floating Aquatic Plants
Floating plants are somewhat easier to treat than the other groups.
Because floating plants are mostly exposed they are susceptable to
topical treatments. Contact herbicides can produce good results on most
species but repeat applications will be required to provide season long
results. Contact Herbicides are almost always used on Water Hyacinth,
and Water Lettuce as they are much cheaper and systemic products are not
often practical on these species. The Duckweeds, Watermeal and Azolla
can be controlled with a systemic herbicide, most commonly a fluridone
based chemical. Fluridone products can provide season long results often
with one application, however there are a tremendous amount of
varialbles to be concidered inorder to have a successful treatment. To
skip ahead to the section on Sonar (41.7% Fluridone Herbicide)
Mechanical meathods are not very effective on floating plants as they
are prone to move with wind and water curents. Additionally the small
size of plants such as Watermeal make physical removal difficult.
Grass Carp are a consideration for Duckweeds as they are a preffered
food, however additional measures are usually required to provide the
Aquatic Plants Factsheets