Vernal Water-starwort (Callitriche palustris)

Vernal Water-starwort (Callitriche palustris) 

The Vernal Water-starwort (Callitriche palustris) is of the order Callitrichales and Water-starwort Family (Callitrichaceae).  This species is one of three species in this family native to Maine. The specimen shown in the photographs on this page was removed from French Hill Pond for study in September 2010. The species name is Latin for swampy or marshy. The order, family and genus names derive from the Greek, carlos and trichos, meaning beautiful hair, referring to the leafy stems. This plant prefers water with a pH of 6.8 or higher. The water in French Hill Pond has a pH around 6.8. Therefore, the environment of French Hill Pond is marginal for this plant.

The leaves are small and pinnately lobed. Each submerged leaflet is elongate, entire, green to brown, about ½ inch (1.3 centimeters) or less long, with a pointed tip and arranged in a dense, staggered-alternate, nearly opposite pattern along the leaf stem. See the photograph below. Leaflets are similarly arranged along the other plant stems, which helps distinguish this plant from similar water plants. The leaves at the top of the plant, above or near the waterline, become broader and ovate. At the very tip of the plant, about six leaves are arranged in a rosette pattern above the waterline.

 

Vernal Water-starwort (Callitriche palustris) Detail 

The flower of the Vernal Water-starwort (Callitriche palustris) is tiny, two-parted, green, forms in the leaf axis and produces an elongated green capsule containing tan seeds.  This plant flowers in the spring, whence its name. The following photograph shows the part of this plant that grows above water. The red arrow points to the flower bud. Note that the leaves are in pairs and each pair is at a right angle to the pair beneath or above. The rosette pattern of the top leaves has not as yet formed on this plant. The submerged leaf formations shown above are barely visible in the photograph below.

Vernal Water Starwort Air Portion

The following photograph shows the floating leaves of a Vernal Water-starwort. The blue arrow points to the rosette of leaves at the top of the plant and the red arrow points to a very small example of the submerged leaves. As the floating part of this plant grows, the pairs of leaves become closer together and smaller. The top leaves are so close as to form a distinct rosette and the plant is too heavy for the stem to remain upright causing the leaves to float. All but the top leaves in the photograph below are actually below water. The leaves in the photographs above and below are less than ¼ inch (6.3 millimeters) wide and one inch (2.54 centimeters) long.

Vernal Water-starwort Floating Leaves

The root system is simple. Some of the roots can be seen in the photograph at the top of the page. This plant roots in mud and can be easily uprooted. It will float around in the pond much like a bladderwort when uprooted.

The Vernal Water-starwort (Callitriche palustris) is very similar to the Northern Water-starwort (Callitriche hermaphroditica) but this later starwort is not found in Maine. The other starworts native to Maine are the Two-headed Water-starwort (Callitriche heterophylla) and a terrestrial starwort, the Terrestrial Water-starwort (Callitriche terrestris). The Two-headed Water-starwort has a rounded capsule and the lower leaflets are rounded at the tip. The Terrestrial Water-starwort has only ovate leaves because it is generally found out of the water.

 

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