Nostoc (Cyanobacteria) in Lawn: Sign of Compacted, Wet Soil

Green, jelly-like patches that dry to black, paper-thin crusts are nostoc, a cyanobacterium often called algae. It doesn't harm grass but indicates compacted clay or silt soil that stays moist and shady—conditions unfavorable for turf. Aerate thoroughly and consider replacing grass with ferns, hostas, or azaleas if conditions can't be improved.

see Nostoc Balls in Grass

nostoc cyanobacteria