Callitriche heterophylla Pursh

Twoheaded Water-starwort

© SRTurner

Family - Plantaginaceae

Habit - Perennial aquatic forb, monecious, rooting at lower nodes.

	Habit.
© SRTurner

	Habit.
© SRTurner

Stems - Glabrous, submerged in water and often forming mats.

	Upper stem and leaves.
© SRTurner

	Mid-stem and nodes.
© SRTurner

	Stems with rooting nodes.
© DETenaglia

Leaves - Opposite, simple, dimorphic. Terminal, floating leaves appearing in small rosettes, with blades spatulate, dark green above and lighter green underneath. Lower stem leaves linear.

	Floating leaves, adaxial.
© SRTurner

	Floating leaves, abaxial.
© SRTurner

	Intermediate leaves.
© SRTurner

	Lower stem leaves.
© SRTurner

Inflorescences - Axillary, sessile, with staminate and pistillate flowers sometimes both present in a single axil.

Flowers - Unisexual, minute, lacking both petals and sepals. Staminate flowers with a single stamen, the filament glabrous. Pistillate flowers hypogynous, the ovary 4-locular. Styles 2.

Fruits - Schizocarps, 0.5-1.0 mm, each breaking into 4 mericarps.

Flowering - February - November

Habitat - Spring branches, streams, ponds, sloughs, ditches, swamps.

Origin - Native to the U.S.

Lookalikes - None close.

Other info. - Despite its small size, this aquatic plant is often noticed due to its unique appearance and, usually, the lack of other vegetation competing for visual attention. It is notable for having two leaf morphologies. Upper leaves floating on the surface of the water are borne in rosettes and are spatulate in shape. Submerged leaves on lower portions of the stem are linear and opposite on the stem. Flowers are borne in the leaf axils, but these are tiny and difficult to examine without a good microscope. The plant can be found both in fresh spring water and in stagnant ponds.

Missouri plants can be referred to var. heterophylla.

Photographs taken near Greer Springs, Oregon County, MO, 6-15-2023 (SRTurner).