Cerastium fontanum Baumg.

Common Mouse-Eared Chickweed

© SRTurner

Family - Caryophyllaceae

Habit - Taprooted forb, usually perennial.

Stems - Sprawling to erect, 10-65 cm, often from a spreading base, usually branched above the midpoint, moderately to densely pubescent with usually straight, nonglandular hairs, occasionally also stipitate-glandular in the inflorescence.

	Stems and leaves.
© SRTurner

	Stem and node.
© SRTurner

Leaves - Opposite, simple, sessile. Blades 0.5-4.0 cm long, spatulate (some basal leaves) or narrowly ovate to oval, angled to a bluntly pointed tip.

	Leaves adaxial.
© SRTurner

	Leaf abaxial.
© SRTurner

Inflorescences - Open panicles, the stalks 0.4-1.0 cm long, 1-2 times as long as the sepals, ascending but usually somewhat curved above the midpoint at flowering and fruiting, densely pubescent with nonglandular hairs, occasionally also with stalked glands, the bracts green, the upper bracts with narrow, thin, white to translucent margins.

	Inflorescence.
© SRTurner

	Inflorescence. Note membranous margin on bract (arrow).
© SRTurner

Flowers - Sepals 5, 4-7 mm long, ovate-lanceolate, angled or tapered to a sharply pointed tip, green, densely pubescent with nonglandular hairs, rarely also stipitate-glandular, the hairs usually not extending past the sepal tips. Sepal margins thin and translucent. Petals 5, 4-5 mm long, 0.6-1.0 times as long as the sepals, deeply 2-lobed (often to the midpoint) at the tip, the veins usually not apparent. Stamens 10. Styles 5.

	Flower.
© SRTurner

	Corolla, stamens, styles.
© SRTurner

Fruits - Capsules 8-11 mm long, 1-2 times as long as the sepals, curved. Seeds 0.6-0.9 mm wide, the surface tuberculate, brown.

	Immature fruit.
© SRTurner

	Dehiscent fruit.
© SRTurner

Flowering - April - October.

Habitat - Sloughs, pond margins, streambanks, ledges of bluffs, sand prairies, pastures, fields, ditches, lawns, gardens, railroads, roadsides, open, disturbed areas.

Origin - Native to Europe.

Lookalikes - Other small-flowered species of Cerastium.

Other info. - The small-flowered species of Cerastium are routinely ignored by all but the most attentive of botanists. They are small, unimpressive, and generally weedy in aspect. Identification is not particularly difficult but requires close attention to detail. C. fontanum is characterized by open inflorescences, sepals which are hairy but not glandular, upper bracts having thin translucent margins, and flowers mostly having 10 stamens. It occurs throughout Missouri, and most of the continental U.S., though less commonly in the Gulf Coast and central Plains states.

Missouri populations belong to ssp. vulgare. Another subspecies, ssp. fontanum, is rarely found outside of Europe and Greenland. It differs in having petals which are noticeably longer than the sepals, and also larger fruits and seeds.

Photographs taken at Weldon Spring Conservation Area, St. Charles County, MO, 5-31-2020, and at Shaw Nature Reserve, Franklin County, MO, 5-31-2021 (SRTurner).