Small Mouse-Eared Chickweed
Cerastium pumilum
Pink family (Caryophyllaceae)

Description: This introduced plant is a winter or spring annual about 2-6" tall. A mature plant becomes tufted at the base, sending up multiple stems. These stems are green and pubescent. The opposite leaves are up to " long and about half as much across. These leaves are broadly oblong or ovate-oblong, green, and pubescent; they have conspicuous central veins, smooth margins, and sessile bases.

The upper stems terminate in small cymes or individual flowers; sometimes the lower cymes branch into secondary cymes of flowers. The peduncles and pedicels of these cymes are light green and pubescent. At the base of each peduncle, there is a pair of green leaf-like bracts. These bracts are broadly lanceolate-oblong or lanceolate-ovate, pubescent, and smooth along the margins; some of the upper bracts have thin translucent margins toward their tips (i.e., they are slightly scarious). These translucent margins are more apparent in mature or dried-out plants than young specimens. The flowers at the tips of the pedicels are up to " across when they are fully open. Each flower has 5 white petals, 5 green sepals, 5 white styles, and 5 stamens with pale yellow anthers. Each petal has several pale lines at its base, while its tip is notched. The sepals are lanceolate and hairy; their margins are translucent. The blooming period occurs during the spring and lasts about 1 month; this is one of the earliest wildflowers to bloom during the spring. The flowers open up during spring days that are sunny and warm. Some plants begin to bloom when they are only 1" tall. Each flower is replaced by a cylindrical capsule containing many small seeds. Each seed capsule is straight to slightly curved; there are 10 small teeth along its upper rim. The seeds are brown, somewhat flattened, and minutely warty or pebbly. The root system consists mostly of thin fibrous roots. This plant spreads by reseeding itself and it often forms small colonies.

Cultivation: The preference is full sun, moist to slightly dry conditions, and sterile soil with little ground vegetation. In Illinois, this little plant completes its growth cycle during the spring.

Range & Habitat: Small Mouse-Eared Chickweed is occasional in central and NE Illinois and uncommon or absent in other areas of the state. It was accidentally introduced into the United States from Europe. Habitats consist of fields, disturbed grassy meadows, areas along roads, barren ground in lawns, and waste areas. Areas with a history of disturbance and environmental degradation are strongly preferred. This little plant tolerates road salt and other run-off chemicals better than most kinds of turf-grass; it also tolerates hardpan clay and gravel better than turf-grass.

Faunal Associations: Like other Chickweeds (Cerastium spp., Stellaria spp.), the flowers of this species attract small bees and Syrphid flies. While the foliage of Small Mouse-Eared Chickweed is potentially edible to rabbits, it is rarely eaten because of its diminutive size and early spring growth. Small granivorous songbirds (e.g., sparrows) may use the seeds as a minor source of food.

Photographic Location: A barren area along a roadside in Urbana, Illinois.

Comments: There are several Cerastium spp. (Mouse-Eared Chickweeds) in Illinois and they are difficult to distinguish from each other. I believe that the species in the photograph above is Cerastium pumilum (Small Mouse-Eared Chickweed) for the following reasons: 1) It is a short-lived annual that completes its life-cycle during the spring, 2) Each of its flowers has 5 stamens and 5 styles, 3) Its flowers always have 5 petals, and 4) Its floral bracts usually lack translucent margins, except for some of the upper bracts on mature plants. Other Mouse-Eared Chickweeds are perennials (e.g., Cerastium fontanum), or they have flowers with 10 stamens (e.g., Cerastium brachypetalum, Cerastium glomeratum), or they produce flowers with 4 petals (e.g., Cerastium diffusum), or all of their bracts have conspicuous translucent margins (e.g., Cerastium semidecandrum).

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