Pond weeds have a number of benefits for the aquatic life that lives where they grow. Many types provide cover to baitfish from predators, cover for predators as they wait to ambush baitfish and shade for fish from the hot summer sun. However, some pond weeds are so invasive that these benefits are not enough to negate how they can interfere with travel and recreation in lakes and rivers or deplete the oxygen supply as they grow in dense mats. It is possible to identify pond weeds by paying attention to their shape, colour and other details.
Look for the beautiful showy flower that is a feature of the water lily. These blooms will have white or pinkish petals and develop on separate stalks from the main leaves. You can identify water lilies without the flowers by the almost foot-wide circular-shaped leaves. These leaves are green above but purple to red underneath and often grow in dense amounts that choke out the shallowest parts of a pond, especially close to the shore.
Recognise hydrilla by the underwater fields of it that will grow in a pond. This invasive species frequently grows from the bottom of a pond and extends either to the surface or to just beneath it. Hydrilla grows on long green stalks with a whorl of small leaves up and down the plant. You will often find hydrilla clogging up your boat propeller or tangling up your canoe paddles as you pass over it. Looking down upon it from on top of the water you will get the feeling you are looking at the canopy of an underwater rainforest.
Identify purple loosestrife from its rows of purple flowers. Loosestrife is an invasive plant found along shorelines of ponds and has a candelabralike shape. The purple flowers grow on the upper stalks, begin to appear in June and can last through the end of August.
Check along the edges of a pond for the heart-shaped leaves of pickerelweed. This plant has large green leaves that resemble the head of a shovel; these leaves often are well out of the water on long stems. You can quickly recognise pickerelweed from the attractive flowers that develop on a separate spike that juts up from the stems of the leaves.
Use the flowers of a water hyacinth to identify this aquatic weed. An invasive plant that originated in the tropics, the water hyacinth has a 2- to 3-inch flower that is lavender with a yellow spot on it. The roots of water hyacinth drop down from the upper part of the plant and absorb nutrients directly from the water. Look for thick floating mats of this weed with oval leaves that have a shiny look to them.