Hort Q&A: What is in my yard?

Carla Smith, horticulture educator
Pottawatomie County Extension Service

What is this in my yard?

I have had three calls in two weeks about this issue. Nostoc, formerly classed as a blue-green algae is now classified as the genus cyanobaterium, may appear in lawns when overwatering or abundant rainfall is present. We have had a wet spring in 2019, 2020, and again in 2021. This jelly like substance can be slippery when it is wet and hydrated. My client mentioned it looked like cooked spinach when wet, a very good description. When it is dry, it turns black and crusty which can prevent stolons or runners from rooting into the soil. This can delay spread and growth of desirable turf grass.

Nostoc does not kill the grass but tends to grow where the turf was already in decline and turf cover is thin. Severe compaction and poor drainage create a perfect storm for growth when we have days and days of rain and cloudy weather. When it dries out, it may seem to disappear. It goes dormant in dry periods, only to ‘come back to life’ with adequate moisture.

If the area is small, simply removing the top layer with a flat shovel can be a relatively quick and easy fix. Once it has spread, it becomes more difficult. So, if you notice this strange substance in your yard, remove it when you see it.

To discourage growth, the best defense is a healthy, actively growing lawn canopy. If an irrigation system is present, make sure it is operating correctly and at the correct intervals. Cut back on irrigation if needed to let the soil dry out more. In the event that rainfall is causing this issue, then take what measures you can to provide for adequate drainage.

Address soil fertility if needed and take a good look at soil and site drainage. Aerification may be helpful in severe cases. Core aeration opens up the soil to better air movement and reduces compaction.

Clemson https://hgic.clemson.edu/factsheet/nostoc/ and University of Georgia https://extension.uga.edu/story.html?storyid=7998 have some good information as they are in humid areas of the country as well.  Use these links for additional information online.  If you have further questions, please give me a call:  405-273-7683 and ask for Carla.

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