Large alga
Starry Stonewort
Nitellopsis obtusa
These illustrations are AI-generated, not photographs, and are not to scale. They show what to look for; they are not a substitute for an expert identification.
How to identify it
Size: Strands can be several feet long. The star-shaped bulbils are only a few millimeters across.
- Not a true plant but a large green alga with a stem-like body.
- Rings (whorls) of long, smooth, bright-green branchlets of different lengths.
- Long gaps between the rings.
- Tiny pale, star-shaped bulbils on the root-like strands near the base. These are the giveaway: gently pull up a clump to look.
Don’t confuse it with
Native Chara, also called muskgrass, feels rough or gritty and often smells musky. Native Nitella has branchlets that fork evenly at the tips and no star-shaped bulbils.
Where it came from
Native to Europe and western Asia.
First found in North America in the St. Lawrence River in the late 1970s, likely carried in ships' ballast water. Pieces and bulbils reach inland lakes on boats, trailers and gear.
Earliest dated Minnesota record: 2015, Lake Koronis, Meeker County. This is the oldest dated record in the USGS non-native species database, not necessarily when it first arrived.
Why it matters
It can grow into thick mats several feet deep that crowd out native plants, cover the areas where fish spawn and make boating and swimming difficult.
Minnesota law
Designated a prohibited invasive species under Minnesota Rules 6216.0250. It is illegal to possess, import, purchase, transport or introduce it, except under a DNR permit for disposal, control, research or education. Named in Minnesota Rules 6216.0250, subpart 2, item M. Minnesota DNR’s summary of these laws.
If you find it
- Don’t move it. Minnesota law requires you to clean aquatic plants and prohibited invasive species off boats, trailers and gear, and to drain all water and leave drain plugs out while transporting. Launching a boat or trailer with aquatic plants, zebra mussels or other prohibited invasive species attached is illegal, and docks, lifts and rafts must stay out of the water for 21 days before going into another body of water. What Minnesota law requires
- Never release bait or pets. Minnesota law forbids dumping bait in any lake or river: put unwanted bait in the trash. Never release bait, plants or aquarium pets into Minnesota waters.
- Report it. Note the exact location, take a photo, and contact the Minnesota DNR aquatic invasive species specialist for your region, or call the DNR at 888-646-6367. Experts there can confirm what you found.
- Ask before removing or treating. Aquatic plants in Minnesota public waters belong to the state. Applying herbicides always needs a DNR permit, and so does cutting or pulling submerged plants over more than 2,500 square feet. When a permit is needed
Minnesota lakes where it has been recorded
39 Minnesota lakes on this site have a record of this species.
Beltrami
Beltrami Lake, Blackduck Lake, Cass Lake, Gull Lake, Lake Bemidji (main lake), Moose Lake, North Twin Lake, Pimushe Lake, Stump Lake, Three Island Lake, Turtle Lake, Turtle River Lake, Wolf Lake
Cass
Bowen Lake, Lake Winnibigoshish, Leech Lake (Kabekona Bay), Leech Lake (Main Basin), Thunder Lake
Crow Wing
Hennepin
Hubbard
Kandiyohi
Pope
A lake that is not listed may still have it. Records exist only where someone found the species and reported it, so “not recorded” does not mean “not present.”
Lake records: the Minnesota DNR List of Infested Waters (September 9, 2026). A lake counts here only where the DNR lists the species as confirmed in that water. Lakes listed only because they connect to an infested water are not counted.
Sources
- Minnesota Rules 6216.0250: Prohibited invasive species
- Minnesota Rules 6216.0265: Permits for prohibited and regulated invasive species
- Minnesota DNR: Minnesota invasive species laws
Earliest dated record: USGS Nonindigenous Aquatic Species database.