Terrestrial Starwort
Callitriche terrestris
Starwort family (Callitrichaceae)

Description: This annual plant consists of sprawling stems with pairs of opposite leaves. The stems are up to 5 cm. (2") long; they are whitish green and occasionally branch. The opposite leaves are 3-4 mm. long and about half as much across; they are medium green, ovate-oblong or obovate-oblong, and smooth along their margins. Each leaf tapers to a short petiole. There are separate male and female flowers on each plant (monoecious) at the axils of the leaves. These flowers are very small (less than 1/8" across) and greenish. Each male flower produces a single stamen, while each female flowers produces a single pistil with a pair of styles. These flowers have neither petals nor sepals. The blooming period occurs from late spring to mid-summer and lasts 1-2 months. The fruit of each female flower is 4-celled; it has a double-ovoid shape (similar to the fruit of a Galium sp.) and a short peduncle. Each cell of the fruit contains a single nutlet. This plant reproduces primarily by reseeding itself; it can reproduce vegetatively by forming rootlets at the axils of the leaves.

Cultivation: The preference is light shade to dappled sunlight, moist to dry-mesic conditions, and barren soil that is devoid of competing ground vegetation. This plant is often found on compacted soil containing clay, glacial till, or rocky material.

Range & Habitat: The native Terrestrial Starwort occurs occasionally in the southern half of Illinois; it is largely absent in the northern half of the state (see Distribution Map). Habitats include barren areas of hilly upland woodlands (particularly those that are dominated by oaks), edges of bluffs, footpaths in wooded areas, shaded gravelly seeps, and rocky riverbanks.

Faunal Associations: Information about floral-faunal relationships for this species is unavailable.

Photographic Location: Along a bluff in Vermilion County, Illinois.

Comments: This is probably the smallest terrestrial flowering plant in Illinois (Lemma minor, or Lesser Pondweed, is even smaller, but it floats on water). To see the flowers and fruits near the axils of the leaves, a 10x hand lens is required. Terrestrial Starwort resembles a low-growing moss, but it is more leafy in appearance. Other species in this genus are submerged or emergent aquatic plants; these Callitriche spp. are referred to as Water Starworts, and they are small in size as well. The submerged leaves of these latter species are linear in shape, but their emergent leaves resemble those of Terrestrial Starwort. While the fruits of Terrestrial Starwort have short peduncles, the fruits of Water Starworts are sessile, or nearly so.