Witch's jelly Nostoc

Cyanobacteria are primitive, rootless plant-like organisms that we generally associate with the green scum that forms in ponds. Nostoc spp. are not plants, but rather cyanobacteria, often referred to as blue-green algae. They form dark green gelatinous masses on persistently moist surfaces such as nursery ground cloth, black plastic, or gravel pads. When wet, these mats of tissue are slippery, creating safety hazards. Without water, plants dry quickly to a flaky brown mass that is easily scraped off, but will return rapidly when irrigation is resumed. Cyanobacteria can be reduced by improving drainage and irrigating earlier in the day, allowing surfaces to dry during the day. No chemical treatments are specifically labeled for these organisms.