How to Get Rid of Lake Weeds
How you get rid of lake weeds depends on two things: what plant you're actually looking at, and how much area you need clear. A small patch of invasive milfoil at your pier is a different job than a native-plant-filled cove that a lake district needs to manage. This guide walks both questions so you land on a method that fits your shoreline and stays inside the DNR's rules.
Step one: identify what you're removing
Native plants get more legal protection than invasive ones, so identification changes what you're allowed to do before you decide how. Two of the most common lookalikes:
Eurasian watermilfoil
invasiveMyriophyllum spicatum
- Feathery leaves in whorls of 4 around the stem
- Each leaflet divided into 12 or more pairs of thin segments
- Stem runs 3 to 10 feet, often reddish and limp out of water
Restricted invasive. Hand removal is permit-exempt statewide; chemical treatment needs an NR 107 permit.
Identification only. Permit rules are on the DNR permit page.
Curly-leaf pondweed
invasivePotamogeton crispus
- Submersed leaves 0.5 to 3.5 in long, alternating along the stem
- Reddish-green, wavy, finely serrated edges, like lasagna noodles
- Reddish-brown stem, 1 to 3 feet
Restricted invasive. Hand removal is exempt; mechanical harvesting or an NR 107 herbicide are the other options.
Identification only. Permit rules are on the DNR permit page.
See the full identification set, all seven plants, on the identification page. Coontail is another common lookalike; see the coontail guide. If it's algae rather than a rooted plant you're looking at, see algae vs. weeds in Wisconsin lakes.
Step two: check whether you need a permit
Hand-pulling inside a 30-foot corridor at your pier, or hand-removing invasives anywhere on your frontage, needs no DNR permit. Anything wider, any mechanical equipment beyond that exemption, and any chemical treatment needs a permit first. Full rules and the decision tree are on the permit page.
Which method fits your shoreline?
Timing matters here too; see seasonal timing for removal before you plan around a specific date.
- Small area at the pier, no permit desired: hand-pulling, inside the 30-foot corridor. Whatever you pull still has to leave the water; see disposal rules.
- Want a permanent clear zone at the dock: a bottom barrier, once permitted.
- Keeping one arc clear year after year, DIY: a weed roller.
- A cove or larger frontage, fast: herbicide treatment, permitted seasonally.
- Large open weed beds, lake-wide: mechanical harvesting, usually a lake-district program.
- Invasive milfoil mixed with native plants you want to keep: DASH, diver-assisted suction. See the DASH guide.
Full cost figures for each are on the cost guide. If you're looking at powered equipment rather than hiring a crew, see what's available to rent.
Method comparison
Hand-pulling
Your time, plus basic tools under about $100
Fits a pier and swim lane inside the 30-foot no-permit corridor, not a weedy cove.
Pros
- Cheap, selective
- No permit in the 30-ft zone
Cons
- Labor-heavy at any real scale
- Snapped milfoil fragments can drift and re-root
Best fit: Pier and swim area, spot-pulling invasives
Herbicide treatment
Roughly $700 to $900 per acre, sometimes more
Covers coves and larger frontages fast; always needs an NR 107 permit, every season.
Pros
- Fast, covers large areas
- Selective products exist
Cons
- Annual cost, seasonal permit
- Doesn't remove the dead plant material
Best fit: Coves, large frontages, invasive knockdown
Mechanical harvesting
On the order of $2,800 per acre
A lake-district or association program, not a single-owner purchase.
Pros
- Removes plants and nutrients
- Covers big areas
Cons
- Expensive, non-selective
- Permit needed; fragments can spread
Best fit: Large open weed beds, lake-district programs
DASH (diver-assisted suction)
Billed by time; roughly 200 to 600 sq ft per hour with a two-person crew
Selective enough to take invasive milfoil while leaving native plants in place.
Pros
- Very selective, removes roots
- Spares native plants
Cons
- Slow
- Costs more, billed by time
Best fit: Targeted invasive milfoil removal