Weeds are bad enough, but lake weeds are a real pain – especially if you’re trying to enjoy the lake or shore. So, what do you do about them? Let’s dive into lake weeds...figuratively, at least.
What are Lake Weeds?
Lake weeds are also known as water weeds, pond weeds, or aquatic weeds.
They are unwanted plants that complete their entire life cycle in the water.
How Did Weeds Get in the Lake?
Non-native aquatic weeds often sprout up in a lake when aquariums are emptied into a storm drain or directly into the lake.
Lakeside dwellers sometimes plant lake weeds to improve the appearance of their waterfront. This was often the case with purple loosestrife, bulrushes, and cattails.
Waterfowl and storm-water runoff can introduce lake weeds. Boaters can also redistribute weeds that attach to their boat in some way.
What Causes Them to Grow?
Overdevelopment of lakefront properties is a major cause of weed growth. Properties that once had trees and shrubs along the lakefront were landscaped, removing the natural vegetation to give owners a clear view of the lake.
Poor water management is another issue. As lakefront properties become urbanized, run-off may not be processed adequately. Those aesthetically-pleasing backyards can negatively affect water quality.
When surrounding grass is fertilized, mowed, and irrigated, this may result in overloading nutrients. This causes increased rates of lake weeds.
Phosphorus from fertilizers can cause high growth in lake weeds.
Types of Lake Weeds
There are a few different types that you should know about so that you can deal with them properly.
Floating Lake Weeds
Algae are often called "pond scum" or "pond moss". It is recognizable because it forms unsightly greenish clumps on the surface of the lake.
Duckweed floats wherever with the wind or water current. It absorbs nutrients from other lake plants via its root system.
Watermeal floats freely. It is the smallest aquatic flowering plant. It looks like green cornmeal.
Water Hyacinth can grow one yard high. Erect stalks support eight to fifteen flowers.
Water Lettuce is common in lakes in the southeast United States. Its growth is so dense that it blocks the sun from submerged plants, offsetting the ecosystem.
Emergent Lake Weeds
Cattails have thickly rooted flat-leaf blades. Stalks are a yard to three in height. They are topped by cigar-shaped cattails.
Water lilies have large heart-shaped leaves. These float on the lake surface. Leaf veins extend laterally. The lily has a single row of bright yellow petals.
Watershield floats on the surface, similar to the water lily. Leaves are one inch and two inches across.
Purple loosestrife is extremely invasive. It grows along the edges of slow-moving lakes and ponds. Plants may grow two to three feet tall. Each plant can have thirty to fifty stems.
Bulrushes are grass-like wetland plants with round, often hollow stems. There are no leaves. Bulrushes grow in large groups or colonies.
Submerged Lake Weeds
Also known as Eurasian Milfoil, Water Milfoil is an extremely invasive submerged perennial. One water milfoil can multiply into two hundred and fifty million new plants yearly.
Hydrilla stems are up to twenty-five feet long. Upper portions of the Hydrilla plant may have two to eight whorls of leaves around each stem.
Naiads grow in still water. Most of these perennials bloom in the spring and early summer.
Bladderwort is a carnivorous aquatic plant with underwater leaf-like stems and several small "bladders". Flowers form on a stem appearing like snapdragons, growing above the lake's surface.
Curly-Leaf Pondweed is green, but it looks reddish-brown in the lake. The leaves are wavy, stiff, and crinkled.
Sago Pondweed is common in lakes and ponds. It sits a yard or two below the surface and is rooted to the lake bottom.
The Clasping-Leaf Pondweed gets its name because its thin, oval leaves appear to be clasping the stem. As the name suggests, this submerged plant’s green leaves are spiny and forked.
The Problem with Lake Weeds
Lake weeds can harm the aquatic environment directly.
They can also affect the health of the eco-environment. Lakes need a balance of plant life. This offsets the available nutrients.
Lake plants usually emerge in the shallower parts. There, they provide food and cover for water birds and fish. Altering the balance between plant life and nutrients negatively affects the lake's health. The resulting oxygen depletion can cause fish to die. Toxic plant blooms may kill wildlife and humans.
Lake weeds restrict the flow of water, causing stagnant water. This is a breeding ground for mosquitoes. Stagnant water also smells and looks bad. Not optimal if you’re trying to boat or swim in the lake!