Lawn fertilizers

The city of Minnetonka along with local watershed districts and the Lake Minnetonka Conservation District (LMCD) promote the use of phosphorus-free fertilizer. (Phosphorus is the middle of the three numbers, i.e. 10-10-10, on a bag of fertilizer. Look for a “zero” in the middle spot).

Most Minnetonka lawns already contain high or very high levels of phosphorus, according to a study conducted by Hennepin Parks several years ago. Results of random soil testing of lawns in Minnetonka, Plymouth, Eden Prairie and Maple Grove show that people who fertilize their lawns apply far too much phosphorus. In general, Minnesota has soils already rich in phosphorus. Putting more phosphorus on a lawn is a waste of money and is harmful to wetlands, creeks, streams, rivers and lakes. One pound of phosphorus entering a storm sewer system can yield 500 pounds of algae growth.

Testing your soil before purchasing any fertilizer will allow you to provide your lawn what it needs, not what is on sale. A soil sample kit is available from the Minnesota Extension Service of Hennepin County, 612.374.8400. For $12.50, the Extension Service will analyze your soil and provide a report to help you make an informed decision on what nutrients your lawn actually needs. (Please note: if you have a newly seeded or sodded lawn, you may need phosphorus to promote root growth.)

Listed below are a few tips on properly applying fertilizer:

  • Do not fertilize until the grass is actively growing and you are ready to mow (mid May).
  • Read and follow manufacturer’s instructions printed on the bag.
  • Never fertilize before a heavy rain. Never apply fertilizer to wet grass, but water thoroughly after application.
  • Fill fertilizer spreaders on hard surfaces where spills can be swept up. Never wash fertilizer spills into the street.
  • Close the gate on the spreader when crossing over hard surfaces such as driveways, walkways, or patios.
  • Rinse the spreader over the lawn, not a driveway or hard surface area.
  • Drop spreaders are more precise, but slower than rotary spreaders. Near shorelines, use a drop spreader.
  • Avoid getting fertilizer into natural drainage areas or pathways where it can be carried to surface water.
  • Near shorelines, leave a buffer of natural vegetation to prevent erosion and retain nutrients.