Man fertilizing lake
Image: WA State Water Quality Consortium

Remember, when you're fertilizing the lawn, you MAY NOT just be fertilizing the lawn!

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Tips for Healthier Lawns and Lakes

Grass clippings contain phosphorus – the nutrient that turns lakes and rivers green.

There has been a lot of talk about using phosphorus-free lawn fertilizer to protect our lakes and rivers. Another source of phosphorus is grass clippings that get blown onto streets, driveways, and sidewalks and don’t get swept up.

One bushel of grass clippings contains enough phosphorus to grow 30 to 50 pounds of algae if allowed to wash into lakes and rivers through the storm sewer.

  • Sweep up! When mowing, direct the discharge chute towards the lawn and away from paved areas. If grass clippings get on paved areas, sweep
  • Mow higher – the height of a dollar bill
  • Keep grass clippings off streets and driveways

Making your lawn healthy

Watch some short video interviews of U of MN Extension horticulture educator Bob Mugaas giving tips on how to improve your lawn in the spring or in the fall.

When is the best time to treat dandelions? Perennial broadleaf weeds, like dandelions and plantain, return year after year from their roots. If you feel you must use herbicides to treat dandelions, it is most effective to treat perennial broadleaf plants in the fall, not during the showy bloom stage.
For more useful lawn maintenance tips download the manual: Turfgrass Maintenance with Reduced Environmental Impacts (2.1 MB pdf), developed by Fortin Consulting, Inc. for the Mississippi Watershed Mgmt Org.

Learn more about lawn care and fertilizer use in the water quality impacts section of this website.

Disposing of Unused Phosphorus (or other) Lawn Fertilizer

Advice from the Minnesota Office of Environmental Assistance, MOEA:

  • Use it in your compost bin or yard waste compost pile. The leaves need the nitrogen to break down and a little phosphorus won't hurt.
  • Use it carefully on your garden and shrubbery (not too much!).
  • If the fertilizer contains pesticides and herbicides do not use it in the compost pile. Take these fertilizers to your nearest household hazardous waste collection site.

    Collection sites:

Here is more information (258 KB pdf) on the 2005 MN statewide phosphorus-free lawn fertilizer law.