How do I get rid of nostoc on my lawn?


Thank you for contacting Toronto Master Gardeners about Nostoc.

Nostoc is a dark blue-green, jelly-like cyanobacterium that is sometimes found in soggy home lawns. It is likely filling in space where grass does not grow, such as areas with compacted soil, excessive moisture, and/or high soil phosphorus levels.

While its jelly-like appearance may be off-putting, it is not harmful to grass or other plants or animals.

Physical removal is a temporary solution, as is the application of products that contain potassium salts of fatty acids that are sold as moss & algae killers. The Nostoc will return until the underlying conditions have been addressed.

To control Nostoc long term, you need to address the underlying environmental conditions that promote its growth.

  • Reduce soil compaction- aerate lawn, add organic matter to help improve soil structure and drainage.
  • Reduce excessively wet areas – eliminate low spots where water collects, fix drainage problems, and reduce watering.
  • Manage phosphorus levels. Test the soil in the area to determine phosphorus levels. If phosphorus is high, avoid fertilizing the area with a phosphorus containing fertilizer (the second of the three nutrient numbers shown on the package).