Pond water-starwort

Pond water-starwort (Callitriche stagnalis)

Small, delicate plants usually found in shallow water and loosely rooted to the bottom. It is an aquarium plant and could be introduced into natural areas through dumping of aquarium vegetation and spread by birds.

Overview

Other names for this plant include:

  • Common names: common starwort, common water-starwort, water chickweed

Ecological threat:

  • Found in shallow waters and may threaten biological diversity by shading and crowding out other species.

Classification in Wisconsin: Caution. This is a non-regulated category.

Species Assessment Groups (SAG) were assembled to recommend a legal classification for each species considered for NR 40. The recommendation for pond water-starwort was based upon this literature review developed by the department.

Identification

Leaves: Opposite; narrow and submersed (up to 10mm wide) with one rounded leaf tip are sometimes present; oval or spoon-shaped floating leaves are up to 10 mm wide; joined by tiny ridges at the base.

Flowers: Tiny; lack sepals and petals; located at the leaf bases on minute stalks; 2-4 tiny whitish bracts emerge from the flower base

Fruits & seeds: Small, located at the leaf bases; four compartments, each containing one seed; oval, 1.2-1.8mm long, 1.2-1.7mm wide, narrow margin all around (wing); bracts at base.

Roots: Fibrous, from plant base or sprouting from stem joints.

Similar species: May be confused with other starworts; to be sure of identification to species, the surfaces of mature fruit need to be examined under 10-20x magnification.

Distribution

See the reported locations of pond water-starwort.

Do you know of additional pond water-starwort populations? Send us a report.

Control

Mechanical: Dredging can deepen a waterbody to a depth where Pond Water-Starwort cannot receive enough light for growth. However, dredging is expensive, particularly if the sediments of a waterbody are contaminated, and require disposal. Cutting Pond-Water Starwort can be viable by the plant fragments must be removed to prevent regrowth. Shading has been successful at impeding growth of Pond Water-Starwort. However, shading an entire waterbody or large areas of a waterbody would be difficult and expensive.

Last revised: Friday December 06 2013