Species and Varieties
Water plants are a natural part of every pond ecosystem. They serve many purposes and are a valuable food source. On this page, find Penn State Extension’s resources on identifying the various types of aquatic plants and algae. In addition, discover advice on planktonic algae and invasive species control.
Types of Aquatic Plants
Aquatic plants are highly beneficial to pond inhabitants. Identifying and understanding the various types of water plants is vital for learning how to manage them. Most aquatic plants are categorized as either submerged, emergent, or floating.
Submerged plants are rooted at the bottom of the pond and grow up through the water column. They grow best in shallower water that allows sunlight to reach the bottom. Popular submerged aquatic plants include elodea and naiad.
Emergent plants are typically found on the pond’s banks and shallow areas. Many of them offer benefits such as helping control erosion along with bank areas and limiting sediment runoff into the water. Cattails and bur-reed are two of the more common emergent plants.
Floating plants float on the water surface and prefer growing in still water. Species, such as duckweed and watermeal, can grow to resemble a thick carpet covering the pond and serve as a food source for waterfowl. Another well-known floating plant is the water lily. Water lily has large leaves and is an ideal habitat for fish and aquatic insects.
Invasive Aquatic Plants
Invasive water plants are often species that out-compete the native aquatic plants. Purple loosestrife is a common invasive species in Pennsylvania. This emergent plant has a showy, purple flower and may cause significant damage by choking out waterways. Other concerning species include hydrilla and European water chestnut.
Using invasive plants in your pond or water garden should be avoided under most circumstances. When choosing a water plant, it is best to select species that are either native to your region or are non-invasive exotic plants. Further information is available in the PA and Mid-Atlantic guide to water species, as well as the free aquatic invasives webinar.
Common Types of Algae
Algae serves as food sources for aquatic life and is an essential part of any pond ecology. In ponds, algae can present itself either as microscopic planktonic algae or as a leafy plant. Planktonic algae causes the water to appear green or brown and often appears suddenly, under favorable nutrient and sunlight conditions. It is considered beneficial and is at the base of the food chain in ponds and lakes.
Filamentous algae is another variety commonly found in Pennsylvania ponds. This dark green plant forms thick mats and gas bubbles. It’s important to note that during the summer months, filamentous algae may reach nuisance levels. Excessive growth may cause damage, as well. This can lead to concerns such as swimming nuisance, interference with fishing, and fish kills.
Nitella and Chara are other common types of algae. Nitella prefers growing in acidic ponds with soft sediments, while Chara prefects more alkaline, hard water ponds. Both varieties are considered valuable and can grow abundantly under optimum conditions. Excessive growth, however, should be promptly managed by reducing or redirecting nutrient sources from the pond.
In this section, discover comprehensive information on identifying and managing different types of algae and aquatic plants. Information on controlling water plants and invasives through biological, physical, and chemical means can be found, as well.
- Videos
Physical Control of Aquatic Plants
Length 4:23There are a variety of physical control strategies that can be employed. Physically harvesting aquatic plants can have a positive, long-lasting effect. - Articles
Facts About Aquatic Invasive Species and Water Gardens
A water garden is fundamentally an outdoor aquarium. The gardener needs to manage the pH, nutrients, and organisms introduced into the system. - Articles
Pond Algae: It's Not All Bad!
Late summer brings questions to Penn State Extension from pond owners about nuisance algae growth. - Videos
Causes and Prevention of Aquatic Plant and Algae Growth
Length 3:24When plants and algae grow abundantly, pond and lake owners often think about ways to eliminate the offending plant. Nutrient control is the long term solution. - Videos
Aquatic Invasive Species in Pennsylvania
Length 12:36Several Aquatic Invasive Species of particular concern in Pennsylvania are discussed, and their identifying characteristics reviewed. - Videos
Aquatic Plant Identification
Length 4:14While aquatic plants and algae may interfere with pond uses, they also serve vital roles in supporting the fish and animal life that make up the pond ecosystem. - Videos
Biological Control of Aquatic Plants
Length 2:50There are a few biological methods, that when applied correctly can be very effective and environmentally friendly to your pond. - Articles
Mid-Atlantic Pocket Guide to Water Garden Species
This information is intended to help select native aquatic plant alternatives and avoid invasive plant species. This guide is intended as a portable reference. - Videos
Chemical Control of Aquatic Plants
Length 7:14Herbicides are often the first thing pond owners turn to when nuisance aquatic plants appear in their ponds. - Videos
Pond Ecology and the Role of Aquatic Plants
Length 3:11This video provides an overview of aquatic plants. - Videos
Identifying Aquatic Plants
Length 6:01This video will look at the four categories of pond plants, and some of the most common aquatic plants that are found in Pennsylvania. - Articles
Water Quality Concerns for Ponds
This is a summary of some common water quality parameters that may cause problems in ponds and how to detect and treat them. - Articles
Pond Ecology
A brief overview of the natural processes of an earthen pond and how to maintain a healthy pond. - Articles
Barley Straw for Algae Control
In recent years, the use of barley straw has become more common as an alternative method for controlling excessive algae growth. - Articles
Duckweed and Watermeal
Duckweed and watermeal are free-floating aquatic plants that are commonly encountered in Pennsylvania. They are commonly found in nutrient-rich ponds with stagnant or little flow. - Articles
Aquatic/Wetland Noxious Weed List
The links below provide a listing of aquatic or wetland plants considered to be noxious weeds by the federal government or Pennsylvania. - Articles
Curly-Leaf Pondweed
One of more than 20 pondweed species (Potamogetons) that occur in Pennsylvania, this invasive plant from Europe frequently grows to nuisance levels in ponds. - Articles
Coontail
Coontail is a common aquatic plant in Pennsylvania ponds and lakes. It has whorls of stiff leaves that get more compact toward the end of the stem. - Articles
Eurasian Water Milfoil
Eurasian Milfoil is an invasive, nonnative, plant with long stems, often reaching to the surface, with feather like leaves in whorls of 4 or 5 around the stem. - Articles
Elodea (Common Waterweed)
Elodea is one of the few pond plants that can remain green all winter long. - Articles
Planktonic Algae
Planktonic algae floats in the water column and can sometimes be confused with muddy water. It causes the water to look green, brown or reddish in color. - Articles
Chara and Nitella
Nitella and Chara look like rooted, aquatic plants, but both are actually a form of algae. - Webinars
Turf and Ornamentals: Aquatics
Length 2 hoursEarn Cat. 9 and PC credits while you learn about aquatic pond plants, water quality, and more. - Guides and Publications$4.00
Management of Aquatic Plants
Understand the importance and benefits of aquatic plants, and learn how to manage them in your pond.