Star jelly
Nostoc commune · Algae
In the water · Photo: Daniel Castanhal García / CC BY
Also called Blue green algae, Mare's jelly, Witch's butter, Nostoc, Nostoc commune
May produce toxins
Only a lab test shows whether a bloom is toxic. Keep people, pets and livestock out of discolored or scummy water until it is tested.
How to identify Star jelly
- Olive to dark green, rubbery jelly sheets on wet ground or shorelines
- Dries to a black, crisp film and swells back to jelly when wet
- Feels like firm gelatin
- Appears suddenly after rain
Similar species
Mare's eggs grow as round balls under water; slime molds are not rubbery and do not swell when wet.
Growth profile
| Season | Visible after rain or snowmelt in spring and fall, drying out in dry spells and reviving when wet. |
|---|---|
| Starts | Cool, wet weather |
| Light | Full sun tolerant |
| Depth | On wet ground and shorelines above the waterline |
| How it spreads or reproduces | Fragments carried by water and foot traffic |
| Habitat | Damp soil, gravel, shorelines, lawns and seasonally wet ground near ponds. |
Why it matters in a lake
Harmless on land in most cases. It fixes nitrogen from the air.
Where it is found
- Idaho: Occasional
- Oregon: Occasional
- Wyoming: Occasional
Classification
| Kingdom | Bacteria |
|---|---|
| Phylum | Cyanobacteria |
| Class | Cyanophyceae |
| Order | Nostocales |
| Family | Nostocaceae |
| Scientific name | Nostoc commune |
More colonial cyanobacteria
Gloeotrichia
Mare's eggs
Rivularia
Warty nostoc
Spirogyra
CladophoraNeed a hand?
Worried about a bloom?
We identify algae under the microscope and test for cyanotoxins, so you know what is in the water and whether it is safe.
Idaho / Wyoming (208) 501-4531Oregon (541) 280-0596