Contrary to most of the aquatic weeds at the Mitchell Mill State Natural Area, Common Water-starwort, Callitriche heterophylla, is a native plant and is not considered invasive. It is a small and relatively fragile plant that inhabits the quiet pools of the higher granitic flat rocks, away from the scouring floods of the Little River. In his 1932 classic The Natural Gardens of North Carolina, B. W. Wells recommended this aquatic plant for ponds in his chapter on Native Wildflowers for the Garden.
The following photo illustrates a large flat rock pool with a population of Common Water-starwort. The main colony is seen primarily on the left side of the pool.
In the Common Water-starwort, floating and submersed leaves have very different forms. The underwater leaves are linear while the floating leaves are much wider and shorter, oval or spatulate (spoon shaped). In the picture below, taken in December 2015, most of the plants show the linear, submersed form with only a few of the floating, wider leaved forms present. The plants are annuals, and just developing over the winter. Small plants that have recently germinated can be seen at the periphery of the main colony.
A closer view of a small plant illustrates the difference in leaf shape. A recently germinated plant can be seen at the bottom right.
As the plants grow and spread in the spring, they begin to mass together, as seen below.
A closer view of fully mature plants shows the typical rounded rosettes of the surface leaves.
Flowers of the Common Water-starwort are located in the leaf axils. They are small and lack petals and sepals. But the plants are remarkably effective at dispersing pollen – by wind when the flowers are above the water, and by water when they are submersed.
Callitriche heterophylla does have a European relative that looks very similar but is not such a good citizen. The European Water-starwort, Callitriche stagnalis, is both alien and invasive in the U.S. Fortunately, it is not found in North Carolina.