Mouse-ear Chickweed is an introduced plant that is widely naturalized from Europe. It can be a perennial or rarely an annual. The stems may be erect, up to 12 inches high but they are frequently sprawling. Multiple stems branch from the base. Those stems that do not flower often will root at the nodes.
The leaves are opposite, oval near the base of the stem and more lance shaped toward the top, stalkless, about 1 inch long and 1/3 as wide, covered with fine hair and with a prominent central vein. Leaves are widely spaced along the stem and leaves of sterile shoots are reverse lance-shaped.
The inflorescence is a small cyme with 1 to 5 flowers. At the base of the cyme are small bracts that have thin dry upper margins. Occasionally the cyme may have glandular hair.
The small flower is 1/3 to 1/2 inch wide, 5 parted, with white petals that are cleft into 2 deep lobes, clawed at the base. The outer green sepals are almost as long as the petals with tips that are somewhat pointed. Each sepal has a prominent dark green vein. There are 10 stamens (rarely 5) with yellow anthers, and 5 styles. The stems of each flower, the sepals of each flower and the stem of the flower cluster are also with fine hair. Usually, only one flower in the cluster is open at a time and the central flower in the cluster is the oldest.
Seeds: Fertile flowers produce a cylindrical seed capsule, with numerous kidney shaped reddish-brown seeds. The capsule retains 10 small teeth at the rim retained from the flower parts, by which the capsule opens to disperse seeds.
Habitat: Mouse-ear Chickweed grows in disturbed areas and fields with moist to dry conditions. It requires sun, but tolerates light shade. It is a frequent visitor to lawns, path edges and roadsides.
Names: The genus name Cerastium, is from the Greek kerastes, meaning 'horn' and referring to the shape of the seed capsule of this genus. The species, fontanum, is a Latin word, referring to springs or running water, which is somewhat obscure since this plant is not a water plant. The subspecies vulgare, means 'common;. The author name for the plant classification - ‘Baumg.’ is for Johann Christian Gottlob Baumgarten (1765-1843) German physician and botanist whose prime work in botany was the study and publication in 4 volumes of the flora of Transylvania.
Comparisons: Other small plants of the same family with white flowers are - Long-leaved Chickweed, Stellaria longifolia where the flower petals are deeply cleft and the leaves 5x as long as wide; and Blunt-leaved Sandwort, Moehringia lateriflora (L.) Fenzl, but there the 5 petals are not notched and the leaves are much longer -up to 2 inches long and the shorter sepals have blunt to rounded tips. Also found around the Mpls/St. Paul metro area are C. nutans, Nodding Chickweed, and C. arvense, Field Chickweed. The closest look-a-like in our area is Common Chickweed, Stellaria media, where the leaves look similar as do the petals, but the sepals are longer than the petals.
Above: Only one flower is open in each cluster at one time. Leaves, stems, flower stalks and sepals are all with fine hair. At the base of the cluster stem are small green bracts (2nd photo). Leaves are stalkless, opposite and widely spaced on the stem.
Below: The petals are clawed at the base and deeply cleft into 2 lobes. The sepals (2nd photo) are more pointed and almost as long as the petals - note the prominent dark green vein. The ten stamens and 5 styles are visible in the 1st photo.
Notes: Mouse-ear Chickweed has been noted on the Garden Census reports as far back as Martha Crone's 1951 census. Mouse-ear Chickweed is established throughout North America. Within Minnesota it is found in most counties in the eastern 2/3rds of the state.
There are three native species of Cerastium (chickweeds) found in Minnesota and two non-natives. The native species are: C. arvense, Field Chickweed; C. brachypodum, Short-stalk Chickweed; and C. nutans, Nodding Chickweed. The introductions are C. fontanum, Mouse-ear Chickweed; and C. velutinum, Large-field Mouse-ear Chickweed, but the latter species, while reported, has no collected specimens. Common Mouse-ear is the only non-native species found here extensively.
References: Plant characteristics are generally from sources 1A, 32, W2, W3, W7 & W8 plus others as specifically applied. Distribution principally from W1, W2 and 28C. Planting history generally from 1, 4 & 4a. Other sources by specific reference. See Reference List for details.
Friends of the Wild Flower Garden, Inc. Text and photos are by G. D. Bebeau unless otherwise credited. "www.friendsofthewildflowergarden.org"