Starry stonewort

Nitellopsis obtusa

Introduced to Koronis Lake around 2015, Starry Stonewort is an aquatic invasive species that has been under constant surveillance by the Lake Association and concerned parties. Read below for more information.

Summarized Information

Found in...

shallow, relatively calm areas of lakes and rivers across a variety of trophic ranges. It favors waters with a high pH and hardness.

Identified by...

its "grass-like" appearance, whorls of 4-6 branchlets off of thin stems, branchlets form asymmetrical forks at the end, clear cells that shallowly anchor it, and antheridia present at all times.


native species and human recreation. Minnesota Aquatic Invasive Species Research Center research has shown dense growth displaces native species and effects the habitat quality of fish and other animals.

What Are We Doing?

The Koronis Lake Association has been hard at work mitigating and reducing the spread of Starry Stonewort. Nitellopsis obtusa is a charophyte [green algae] and not a angiosperm [flowering plant], so it must be pulled out in its entirety or else it regrows. The mechanical puller does this well and is at work in the lake for many months. Additionally, an algaecide is administered to the lake in treatment areas. Reports with more information can be found at the bottom of the page.

What Can You Do?

We still need your help to protect our lake. You can help by ensuring that any equipment or recreational items that are in the water are cleaned according to DNR regulations. More information on DNR laws and regulations can be found below.

Starry Stonewort Lookalikes

Some native species can resemble Starry stonewort but don't have the harmful impact of the non-native Starry stonewort.


Nitella is closely related to Chara but prefers deeper water. Nitella is smooth to the touch and does not emit a musty or garlic odor. Nitella also has six to eight branchlets along the internodes, but these branchlets will have additional lateral and terminal branches that create a bushy appearance. 


Commonly called “musk-grass,” Chara can form extensive beds of “moss” in clear, shallow water. Beds may be a few inches to several feet deep. Plants are anchored to the substrate by false roots, or rhizoids, which are typically colorless. Chara is easily distinguished from other macroalgae by its rough texture and strong musty or garlic-like odor. Individual internodes, or false stems, will have whorls of six to eight branchlets that do not have further branching.  

Water Stargrass

Water stargrass is grass-like with thin branching dark-green stems and alternate leaves with no prominent midvein. Water star grass can grow up to 6 feet long and can form floating colonies.

Flowers rise above the surface and are bright yellow, star-shaped, with 6 narrow petals. Water stargrass reproduces from seeds and through fragmentation. A slender, multi-branched stem grows from the buried rhizome. Alternate leaves and a rounded stem can help distinguish from flat-stem pondweed. Distinctive yellow, star-shaped flowers provides basis for its common name.

Sago Pondweed

Sago pondweed grows from thickly matted rhizomes. All leaves are submerged below the water line and alternately arranged on the steam.

Sago Pondweed leaves are highly branched, stiff, narrow (about 1/16" wide) and thread-like (2" -12" or more in length). Resembling pine needles, each leaf ends in a sharp point. Spreading leaves resemble a fan with an overall bushy appearance. Nutlets (approx. 18" - 14" long by 1/10" to 1/8" wide) appear like beads on a string. Tiny green flower appears on a spike along with nutlets above the water surface.

Koronis Lake Association & Minnesota Aquatic Invasive Research Center

Lake Koronis Starry stonewort Reports

Year-End Reports

Management Reports