Tips to put autumn leaves to work and curb phosphorus runoff

MADISON — With autumn now in full swing, many of us are preparing for some time outdoors with rakes and leaf blowers to clear the lawn. However, it’s important to understand the connection between fallen leaves and the algae blooms we have been seeing each summer in Wisconsin’s lakes.

Leaves contain phosphorus, and can contribute to phosphorus runoff. Luckily, there are easy methods to benefit both the environment and your lawn and garden.

“Just one pound of phosphorus can make up to 500 pounds of algae in our lakes, so even the simple, everyday things we do at home can make a big impact,” said Tyson Cook, director of science and research for Clean Wisconsin. “The images of a bright green Lake Erie this summer are not foreign to Wisconsin, where nearly a quarter of our impaired waters are overloaded with phosphorus.”

The longer leaves sit exposed to rain in piles on the curb, the bigger the chance they’ll contribute phosphorus to runoff that will make its way to the lakes. You can reduce phosphorus loss from leaves by reducing their exposure to rain. Best practices include putting leaves out shortly before pickup to minimize leaching (check the leaf pickup regulations in your community). Another option is to take the leaves directly to a yard waste collection site. Covering leaves with a tarp until pickup also can help.

Many municipal programs throughout Wisconsin are designed to help. Check with your city or township for ecologically friendly suggestions such as:

  • Mowing – By cutting the leaves into small bits, it enables them to fall beneath the grass canopy and nourish the soil while providing food for beneficial insects and microbes.
  • Composting – Leaves can be mixed into a compost pile throughout the year along with grass clippings and fruit and vegetable scraps. Composting carries many benefits for a home garden, from improvement of soil quality to a better resistance of plant diseases.
  • Mulching – Shred the leaves to pile atop the annual garden or around perennials plants and shrubs for insulation and protection. Remember to till the leaves into the garden come spring. There’s an added benefit here – money may not grow on trees, but this cost-free mulch does.

Phosphorus pollution is one of the largest causes of water quality problems in Wisconsin, and the primary source of phosphorus is polluted runoff.  Phosphorus reduction efforts like the Yahara WINS pilot project in Dane County are exploring runoff control strategies like urban leaf management to improve water quality.