Cerastium L.
Family: Caryophyllaceae
Mouse-Ear Chickweed
Cerastium image
Steve C. Garske  

Key to Wisconsin Cerastium

    • 1a.Stems, leaves, and sepals densely covered in white tomentose hairs C. tomentosum

    • 1b.Stems, leaves, and sepals covered with straight or irregular hairs, not white, sometimes glandular 2

    • 2a.Leaves usually with axillary clusters of leaves present; leaf blades linear to narrowly oblong or lanceolate; petals showy, 2–3 times as long as the sepals; anthers 0.8–1.1 mm long 3

    • 2b.Leaves without axillary clusters of leaves present; leaf blades narrowly to broadly ovate to elliptic; petals shorter than the sepals or barely longer; anthers less than 0.7 mm long 4

    • 3a.Cauline leaves all similar in size and shape (except the most basal ones); mid-cauline leaves 0.5–3 mm wide, apex acute (rarely obtuse); petals 7.5–12.5 mm long C. arvense

    • 3b.Cauline leaves largest at mid-stem, those at the distal and proximal ends smaller in size; mid-cauline leaves 3–6 mm wide, apex obtuse; petals 10–15 mm long C. velutinum

    • 4a.All inflorescence bracts completely herbaceous, glandular-puberulent even at the tips; pedicels often distinctly arched below the calyx 5

    • 4b.Distalmost inflorescence bracts with narrow to broad scarious margins at the tips, the tips glabrous or sometimes with a few non-glandular hairs; pedicels slightly if at all curved 6

    • 5a.Leaves less than 1 cm long, apex obscurely acute; pedicels equaling or shorter than the capsules, deflexed proximally C. brachypodum

    • 5b.Leaves 1 cm or longer, apex distinctly acute to acuminate; pedicels much longer than the capsules, deflexed distally C. nutans

    • 6a.Plants covered in eglandular hairs, rarely with glandular hairs; sepals lacking or rarely with sparse glandular hairs; petals deeply cleft, almost to their bases; stamens 10 C. fontanum

    • 6b.Plants covered in both glandular and eglandular hairs; sepals glandular-pubescent; petals shallowly notched; stamens 5 7

    • 7a.Bracts and sepals scarious for, at most, the apical 1/4; petal veins forked; seeds covered with acute to blunt papillae C. pumilum

    • 7b.Bracts and sepals scarious for at least the apical 1/3; petal veins unforked; seeds smooth or with small, rounded papillae C. semidecandrum

This genus is distinctive in fruit: the usually slightly curved capsules open at their apices via 10 distinct little teeth. Most of our species bloom early in the spring and specimens with both mature fruits and flowers can easily be found. Rabeler & Cusick (1994) provide notes on some of our annual species as well as others that could potentially occur in Wisconsin.
Species within Monroe County 2016