Grass Clippings Impact your Pond
All plants require nutrients to grow, specifically nitrogen and phosphorus. These nutrients are found in all living things and therefore are cycled back into the environment after they die. For this reason, animal waste, leaves, soil, fertilizers, and grass clippings can all contribute significantly to the nutrient levels in the pond and thus, drastically increase the growth of weeds and algae. Studies have shown that one bushel of fresh grass clippings can contain 0.1 pounds of phosphorus which if it ends up in lakes or ponds is enough to produce 30 to 50 pounds of algae.
Experts suggest you should mow your lawn to 3”, and to remove 1/3 of the blade length per mowing. Most of the nutrients are found in the top part of the blade so this reduces the amount of nutrients made available to the environment while simultaneously increasing the health of your lawn. This also helps reduce the amount of bare soil in your yard, which can supply excessive nutrients to your pond during runoff events.
If possible, leave several feet of un-mowed grass around the edge of the pond to provide a slight buffer from any runoff nutrients or plant matter. At the very least, try to blow the grass clippings away from the body of water or bag and remove them all together. Also keep grass clippings off the streets and sidewalks, as these runoff into the drains and deposit directly into our bodies of water.
Leaving clippings on the lawn can act as a natural fertilizer, reducing the need and cost of additional fertilizer applications. While this practice is thought to increase the risk of thatching, excessive nitrogen fertilization and infrequent mowing are the predominant causes. If you must use additional fertilizers on your lawn, try to use those with low NPK ratios or organic alternatives to help reduce nutrient loading and runoff.