Common Mouse-Eared Chickweed
Cerastium fontanum
Pink family (Caryophyllaceae)

Description: This introduced perennial plant is tufted at the base, producing multiple stems up to 1' long, although they are usually about one-half of this length or less. These stems are ascending to widely spreading; they are green or purple, terete (round in cross-section), and pubescent. The opposite leaves are up to 1" long and 1/3" across (or a little larger); they are variably shaped, including lanceolate-ovate, oval-oblong, or broadly oblanceolate. The leaves are pubescent, smooth along the margins, and sessile at the base; they have a prominent central vein on the upper surface. The stems often terminate in small cymes (flat-headed clusters) of 1-5 small flowers; both the peduncles and pedicels of these cymes are pubescent. At the base of each cyme, there is a pair of leafy bracts with thin translucent margins. Each flower is up to " across, consisting of 5 green sepals, 5 white petals with notched tips, 10 stamens with pale yellow anthers, and 5 styles; some plants may produce flowers with fewer than 10 stamens. The sepals are lanceolate, pubescent, and translucent along their margins; they are about the same length as the petals. The blooming period occurs intermittently from late spring to early fall and may last several months for individual plants. Each flower is replaced by a cylindrical seed capsule with 10 small teeth along its upper rim. Each seed capsule containing several small seeds. The seeds are somewhat flattened and minutely warty or pebbly. The root system is mostly fibrous. This plant reproduces primarily by reseeding itself; it can also form vegetative offsets when the nodes of the lower stems develop rootlets while lying on moist ground.

Cultivation: The preference is full sun to light shade and moist to slightly dry conditions. This plant can tolerate a broad range of soils, including those that contain loam, clay-loam, and pebbly or gravelly material. Common Mouse-Eared Chickweed is more often found in fertile soil than other Cerastium spp. (Mouse-Eared Chickweeds). It is a larger plant that can tolerate more competition from other kinds of vegetation.

Range & Habitat: Common Mouse-Eared Chickweed occurs in every county of Illinois; it is quite common (see Distribution Map). This species was introduced from Eurasia. Habitats include fields, pastures, lawns, gardens, roadsides, areas along railroads, areas adjacent to buildings, vacant lots, degraded grassy meadows, and waste areas. Areas with a history of disturbance provide preferred habitats.

Faunal Associations: The flowers attract various bees and flies; these insects suck nectar primarily, although some Syrphid flies feed on the pollen and some of the smaller bees (e.g., Halictid bees) collect pollen for their larvae. The caterpillars of several moths feed on the foliage of Chickweeds (Cerastium spp., Stellaria spp.), including Agrostis venerabilis (Venerable Dart), Haematopis grataria (Chickweed Geometer), and Lobocleta ossularia (Drab Brown Wave). Sparrows and other small granivorous songbirds eat the seeds of Chickweeds. Because Common Mouse-Eared Chickweed is one of the larger Chickweeds that grows during the summer, the Cottontail Rabbit nibbles on its foliage occasionally.

Photographic Location: An area adjacent to a building in Champaign-Urbana, Illinois.

Comments: This adaptable plant is probably the most common Cerastium sp. (Mouse-Eared Chickweed) in Illinois. Compared to the similar Stellaria spp. (Chickweeds), Mouse-Eared Chickweeds usually have more pubescent leaves and their flowers have 5 styles, rather than 3. Among the many Mouse-Eared Chickweeds that occur in Illinois (most of them are introductions from Eurasia), Common Mouse-Eared Chickweed is the only one with a perennial habit and it is often larger in size. It also blooms later in the year (typically during the summer), while the annual species of Mouse-Eared Chickweed bloom primarily during the spring. A scientific synonym of Common Mouse-Eared Chickweed is Cerastium vulgatum.

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