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Pond Weeds

This wet weather and humidity have pond weeds growing like, well, weeds!

Nashville, Ark. – What have I been up to these last couple of weeks? POND WEEDS! This wet weather and humidity have pond weeds growing like, well, weeds! There are many types of aquatic weeds, but in comparison to pasture and turf grass weeds, aquatic weeds can, on occasion, be easier to identify. There are four main types of aquatic weeds: algae, emergent, floating and submersed. 

Algae common to Southwestern Arkansas includes filamentous and planktonic algae. Filamentous algae, sometimes called moss, although it is not truly considered to be a “moss”, can blanket pond bottoms and clumps of it can float to the surface. Planktonic algae are the microscopic plants that at high concentrations can make water appear green. These algae blooms can be red, black, or green.

Some common emergent weeds are alligator weed, water pennywort, and smart weed. Alligator weed is a non-native species, therefore we should be careful to not allow this to spread. It forms very dense stands or mats, making shoreline access difficult. Stems are hollow, leaves are opposite, and include a prominent mid-rib. The flowers are small and white on long branches, resembling white clover. Water Pennywort usually forms dense mats along shorelines, but can also be floating mats or islands. Leaves are dark green and round with blunt indentations rising from a center stem. Tiny white to greenish-white flowers with 5 petals arise from a single point on the stalk; to me, they somewhat resemble a 4-leaf clover. Smart weed can grow up to 3 feet tall and form dense colonies in shallow water. Stems are jointed, leaves are alternate, and up to 4 inches long. Flowers are green and then turn white or light pink as the mature.

Duckweeds and Watermeal are two of the most common floating weeds in Southwest Arkansas. Water Hyacinth is a nonnative species, but is slowly becoming more common to the area. Duckweeds form dense blankets that cover the surface of still water. They range in color from light green to dark green and they have flattened leaf-like structures with hanging roots. Leaves are small, about the size of half a Tic-Tac. Watermeal is much smaller; it is a rootless plant that looks and feels like green cornmeal. It forms dense blankets that cover still water. Its “leaves” are about the size of a pin head. Water Hyacinth forms large floating masses that have deep green leathery leaves with spongy stems and feathery roots. The flower consists of 5-20 light purple to blue flowers with the upper petals having a pronounced yellow spot. These plants are popular in landscaped ponds, as the flower is actually very pretty.

One of the worst submersed weeds is Hydrilla. It is a non-native species; however, it grows quickly and has already built up a resistance to some chemicals. Hydrilla leaves are oblong with sharply serrated edges; leaves are rough to the touch. They are green and grow in whorls of 3-8. Flowers grow from the upper branches and are translucent to white in color. Two other common submersed weeds that are native include Coontail and any of the “pondweeds” (yes, that is a specific type of aquatic weed). Coontail is rootless, submersed and can grow 15 feet tall. It forms dense colonies. The stems are elongated, branched and rough to the touch. The leaves are whorls of five or more and somewhat resemble the tail of a raccoon. Different types of pondweeds are Sago, Illinois, and Variable leaf. Sago pondweed has no floating leaves; stems are thin and have filament-like leaves. They can grow over 12 inches long. Illinois pondweed has mostly submersed leaves. Leaves are blade-like, submersed leaves are 1-7 inches long and 2-3 inches wide. Variable leaf pondweed has both floating and submersed leaves. Floating leaves are leathery, elliptical. Submersed leaves are much thinner and threadlike.

Common chemicals include copper sulfate for algae. 2,4-D is commonly used for some emersed weeds, however Fluridone is popular for both emersed and submersed weeds as well as some floating weeds. Glysophate is another chemical for treating most shoreline vegetation and several emersed weeds. Diquat is also readily available; it is commonly used for submersed weeds and filamentous algae.

The most important point to remember is to read the chemical label thoroughly; do not assume that all instructions are the same for all chemicals. It is also important to learn your surroundings when applying chemicals. Be aware of the upcoming weather; will it be windy? Could my chemical application drift over to my neighbors? Know what your end goal is. What are the uses for my pond? Do I have fish colonies I want to protect? Do I have cattle drinking water out of this pond? These are all factors that could affect your livelihood. Without a doubt, the best piece of advice I can give is to not be in a hurry. Do not apply chemical to the entire pond at once, as that might result in a fish kill. Again, go back to the label and see what it indicates for use when fish are present. And lastly, please always feel free to contact the Extension Office at 870-845-7517 for more information. Information for this article was obtained from UAEX publications, MP360, “Farm Pond Management” and from Southern Regional Aquaculture Center, “Aquatic Weed Management.”

By Kaycee Davis
County Extension Agent - Agriculture
The Cooperative Extension Service
U of A System Division of Agriculture

Media Contact: Kaycee Davis
County Extension Agent - Agriculture
U of A Division of Agriculture
Cooperative Extension Service
421 N. Main Nashville AR 71852
(870) 845-7517


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