Surface Water Management Division

LakeWise Lawn Care

Having a well manicured lawn is important to many homeowners, but is not the best landscaping option if you live on or near a lake.  Fertilizers and pestices used for lawn care will be washed into your lake during rain storms.  Replacing some of your lawn with native vegetation is the better option.  However, if you have a lawn, follow the tips below or use natural lawn care practices.

Choose a lake-friendly fertilizer

Unfortunately, fertilizers not only promote the growth of your lawn, they also can fertilize the lake.  When the fertilizers are washed into the lake during a rainstorm, they promote excessive weed and algae growth in your lake.  Fertilizers consist of three main ingredients - nitrogen, phosphorus, and pottasium.  Lakes are extremely sensitive to phosphorus, in particular.  If you can avoid it, simply don't fertilize your lawn.  However, if you feel your lawn is showing signs of needing fertilizer you can do it in the following lake-friendly ways:

Choose a phosphorus (P)free fertilizer - Lawns don't need phosphorus once they are established because soils in the area are rich in phosphorus.  By picking a phosphorus-free fertilizer you are helping your lake without sacrificing your lawn.  Most retailers have phosphorus free options.  Look on the bag label for three numbers and choose the brands with the zero in the middle column (see example).  If you use a lawn care service - request a P-free fertilizer.

Click on picture to enlarge

• Choose a slow-release fertilizer - By choosing a slow release or organic fertilizer you can reduce the amount of fertilizer washed away and reduce the frequency of having to feed your lawn.
• Clean up any spills - If you spill some fertilizer on your driveway or other hard surface - clean it up to avoid it washing into the lake.
• Follow the product guidelines - when it comes to fertilizers more does not mean better.  Stick with the instructions on the product bag.  

Avoid Weed-N-Feed Products

Using combination weed-n-feed products can lead to excessive nutrients and pesticides entering your lake.  In addition, these products typically do not work well together.  Fertilizer needs rain to help release it into the soil.  However, the herbicides in weed-n-feed products easily wash off in rain.  Try instead to fertilize as needed.  Then spot treat the problem weeds with an approved herbicide (never during or before rain).  This will minimize herbicide use and save you money.  

Mow Your Lawn Less Frequently

Leaving your lawn 3 inches or longer can benefit your lawn and your lake.  Longer grass helps to shade the roots to promote healthier grass.  Longer grass also helps to prevent soil erosion and better traps nutrients that might otherwise wash into the lake.  Fewer mowings also save you time and money. 

Leave Your Grass Clippings

When you are mowing your lawn, let your grass clippings return to the lawn.  The clippings will decompose providing a homemade slow release fertilizer for your lawn. 

Create a buffer of lakefront vegetation

Having lawn right up to the lakeshore leaves your lake exposed to sources of nutrients and pollutants that wash into the lake. Lawns also has very shallow roots that allow for your shoreline to easily erode. Leaving or planting a buffer of native vegetation at the lakefront with the lawn behind it is the best way to protect your lake. Find out more about lake shoreline buffers.

Lake Friendly Lawn care Resources

Natural Yard Care - Snohomish County Surface Water Management

Lake Friendly Gardening: Tips for Homeowners Living in the Lake Whatcom Watershed (external): An extensive guide developed by the good local resource developed by the WSU Cooperative Extension and others (external)

Grow Safe Grow Smart (external):  A consumer guide to lawn and garden products - 600 pest controls and fertilizers reviewed for health and environmental hazards.  Includes information on brochures alternative pest treatments, choosing smart fertilizers, and more - from the Local Hazardous Waste Program in King County, WA and the Metro regional government in Portland, OR

Lawn To Lakes Organization - tips for green lawns not green lakes (external): 

Lawns Green, Waters Clean (external):  Resources for having a healthy lawn with phosphorus-free fertilizers from the Maine Department of Environmental Protection 

Natural Lawn Care - King County (external):  Information on natural lawn care and landscaping that is easier to care for and healthier for families, pets, wildlife and the environment - including lakes.

Contact:

Gene Williams, Senior Planner, 425-388-3464 extension 4563

Marisa Burghdoff, Water Quality Specialist, 425-388-3204

Jen Oden, Water Quality Specialist, 425-388-3464 extension 4352