Flower:

Plants rarely flower, but will float on the water's surface when they do. Flowers are contained in a lateral pouch, lack petals or sepals and have 2 stamens and a single style.

Leaves and stems:

Leaves, known as fronds, are 3 to 15 mm (to ½+ inch) long, 2 to 3.5 times as long as wide, narrowly egg-shaped to oblong-elliptic, blunt to rounded at the tip, often with a few minute teeth at the tip end (magnification required), and tapering at the base to a flat stem. Color is usually green, sometimes purplish. A frond may have a single, thread-like root up to about 1 inch long, though roots may be absent altogether.

Branched chains are formed with offshoots from a frond, which then offshoots another one or two stems and fronds and so on, a single chain having up to 50 fronds. Vegetative plants float just below the water's surface, not on the surface, and often form dense, tangled masses with thousands of chains.

Fruit:

Like the rare flower, fruit—a tiny seed less than 1 mm long—is rarely produced.

Notes:

Star Duckweed is very common in Minnesota and not likely to be mistaken for any other species; the leaf shape and branching chains are quite distinctive. It may be overlooked since it is rarely seen floating but there is no mistaking it once you get a closer look. Like other Duckweeds, it's found in the quiet waters of lakes, ponds and slow-moving streams.