Having an acceptable level of aquatic vegetation in a pond is certainly a good thing. Aquatic plants photosynthesize and help add oxygen to the water. They also provide essential habitat for fish, contribute to the diversity of the pond ecosystem, and provide food for some animal species.
But too much aquatic vegetation can cause some serious problems. When pond weeds consume the majority of the pond surface, sunlight is unable to penetrate the water and the free exchange of gases with the water surface if limited. Ideally we like to see 20% aquatic vegetation cover in a pond.
When aquatic vegetation coverage is greater than 20%, rapid expansion of pond weeds can quickly cover a pond in the warm months. When aquatic vegetation coverage is less than 20%, prey species like bluegill don’t have many places to hide and prey species like largemouth bass aren’t able to ambush prey.
Below we’ll explain the four main types of aquatic vegetation that can become pond weeds. We hope these characterizations will help you better identify any weed issues you might be having, and what you can do to manage them.
Algae and Other Phytoplankton
Algae are the most primitive pond weeds as they do not have true roots. Some photosynthetic plankton (phytoplankton) are microscopic and not visible to the naked eye. But their presence is usually easily to detect simply based on the color of the water in the pond. If the water has a green tint to it, there’s likely a strong population of phytoplankton.
The most familiar type of phytoplankton or algae is filamentous algae, also known as pond scum. This type of algae is characterized by long, thread-like structures that form dense clusters of slimy strands. We mostly see filamentous algae in ponds, but we will occasionally find it in pockets of slow moving rivers and streams.
Like many other pond weeds, filamentous algae have the ability to grow rapidly when conditions are favorable. The list of favorable conditions include sunlight, warm water, and nutrients (particularly nitrogen and phosphorous). This is why algae cover is much more prevalent in the summer months.
While filamentous algae can play a positive role in a pond ecosystem by contributing to the pond food web and adding oxygen through photosynthesis, excessive algae growth is usually a problem for a pond. Dense mats of algae block sunlight, impede the growth of other aquatic plants, and deplete oxygen levels in the water. All of these negative effects can harm fish and other aquatic organisms.
Floating Pond Weeds
As the name suggests, floating pond weeds do not have roots that attach to the pond substrate. They have roots that dangle in the water and a vegetative portion of the plant that sits above the pond surface. Floating pond weeds have evolved different strategies to adapt to a life without soil. Instead of rooting in the substrate, they derive nutrients directly from the water.
This adaptation allows them to thrive in nutrient-rich environments, but it also makes them susceptible to changes in water quality and nutrient levels. In some cases these floating plants can become invasive and cover large areas of water, impacting the ecosystem and recreational use of ponds and lakes. Therefore, managing their growth may be necessary in certain situations.
Some of the most problematic floating pond weeds we see are duckweed, water hyacinth, and bladderwort. Duckweed is a tiny, floating plant with roots that hang in the water. It reproduces rapidly and can quickly form dense floating mats on the water surface.
Water hyacinth is a rootless floating plant with bulbous, inflated stems that help it float. It has feathery roots that absorb nutrients from the water. Bladderworts are unique in that they have tiny bladder-like structures on their stems that trap and digest small aquatic organisms. These plants do not anchor in the soil but float freely, relying on their buoyant stems.
Submerged Pond Weeds
Submerged pond weeds can be some of the most difficult to control. These plants have roots anchored in the pond substrate, which they use to obtain nutrients from the rich pond sediment. The vegetative portion of these plants does not typically sit above the pond surface, although sometimes dense populations will have submerged plants laying on the pond surface.
These plants don’t have the vascular tissues to support growth above the water surface. This is why they only grow below the water, where strong stems are not necessary. This is also why they easily fragment when hit with a trolling motor or outboard engine.
There are many species of submerged pond weeds, but the ones we see most often are elodea, hydrilla, watermilfoil, and coontail. These species tend to be more prevalent in ponds that have clear, infertile water. Because the water clarity is high, sunlight is able to penetrate deeply into the water and help these submerged pond weeds thrive.
Biological control is possible through fertilization, which feeds the plankton and reduces water clarity. We can also control these submerged pond weeds by stocking triploid grass carp, but it’s important to note that grass carp don’t eat all species of submerged weeds. We can also control these weeds with our underwater spraying rig, but it usually takes several applications to regain control of an overgrown situation.
Emergent Pond Weeds
Emergent plants are rooted in the pond substrate, but also have a vegetative portion that sits above the water. These pond weeds include cattail, horsetail, spikerush, alligator weed, water lily, and more. These are some of the easiest pond weeds to manage because they can be sprayed on the pond surface.
Emergent pond weeds are usually found around the edge of ponds. Because their roots much be anchored in the pond substrate, these plants are typically growing in shallow areas of the pond. They’re not prone to develop in deeper portions of the pond where their roots would have to be significantly longer.
Emergent pond weeds can reproduce in a variety of ways. Some species have flowers that are above the water surface. When these flowers are pollinated, they produce seeds that allows the plants to reproduce. Those seeds will be dispersed by wind, water currents, or animals, or may simply fall into the water and form a new plant.
Other species, such as cattails, reproduce vegetatively through the growth of rhizomes or runners. These are underground stems that give rise to new shoots and roots. As they spread horizontally along the pond substrate, they can produce new shoots and establish new colonies in nearby areas. This type of reproduction allows some emergent pond weeds to spread rapidly and dominate sections of a shoreline.
Another way emergent aquatic plants can reproduce is through vegetative fragmentation. This occurs when parts of the plants break off the parent plant and develop into new individuals. Fragmentation may be caused by physical disturbances such as wind, wave action, or human activities.
Let Up Help Improve Your Pond!
If you’re in the south GA or north FL areas and need help with unwanted aquatic vegetation on your pond or lake, complete this form and we’ll contact you to schedule a time to meet. We look forward to turning your pond into a productive fishery for years to come!