Mezereon

A spring annual with small sessile axillary flowers. From 400-2800 m alt.s.m.

Thymelaea passerina is considered a noxious weed in the NW United States.

Erect annual up to 55 cm tall. Stem glabrous, woody below. Leaves alternate, less often opposite, 8-25 mm long, 2-3 mm broad, linear to lanceolate, glabrous, sessile. Flowers greenish yellow, c. 3 mm long, axillary solitary or in clusters of 2-3, sessile, base with dense white hairs; bracts 2, c. 1.5 mm long, ovate. Calyx tube c. 2 mm long, pubescent, 4 lobed; lobes c. 1 mm long, ovate. Stamens 8, upper 4 antisepalous. Ovary c. 1.8 mm long, ovoid, pubescent above; style less than 1 mm long; stigma capitate. Fruit ovoid, c. 1.6 mm long, black, enclosed within the persistent remains of calyx.

Herbs annual, erect, (10-)40-70 cm tall. Primary root rarely branched, yellow-brown. Stem usually single, erect, branched from above base, green, terete, slender, base slightly woody, glabrous or rarely puberulous. Leaves alternate; petiole very short to nearly absent; leaf blade green on both surfaces, linear-lanceolate or narrowly lanceolate, 0.5-2 × 0.1-0.25 cm, herbaceous, abaxially puberulous, margin not revolute, apex acuminate; midrib inconspicuous, lateral veins obscure. Inflorescence an axillary cluster of 1-5 flowers; bracts 2, leaflike, green, lanceolate, 2-3 mm, margin proximally sparsely whit e ciliate, apex acuminate, pubescent. Pedicel short, pubescent. Calyx yellowish green; tube 2-3 mm, exterior whitish pubescent, long white ciliate at base; lobes 4, ovate, 0.5-1 mm, apex obuse. Stamens 8, both whorls inserted above middle of calyx tube; filaments very short; anthers oblong, ca. 0.4 mm, included within calyx tube. Disk absent or reduced. Ovary ovoid, with short, thick hairs at apex; style terminal; stigma capitate, slightly papillate. Drupe green, ovoid, 2-3 mm, indehiscent; enclosed in persistent calyx; epicarp membranous. Fl. May-Aug, fr. Jul-Oct. 2n = 18.

Distribution: Europe, Caucasus, Mesopotamia, Turkey, N. Africa, C. Asia, Altai, Afghanistan, Iran, China, W. Pakistan, Kashmir.

C and W Xinjiang [Afghanistan, Kashmir, W Pakistan, Russia (W Siberia), Turkmenistan, Uzbekistan; N Africa, SW Asia, C, E, and S Europe; naturalized in S Australia and North America].

Fl. Per. March-April.

Near farm fields, livestock farms, saline hillsides, dry river beds; 400-1000 m.

Stellera passerina Linnaeus, Sp. Pl. 1: 559. 1753; Ligia passerina (Linnaeus) Fasano; Passerina annua Wikström; S. annua Salisbury; Thymelaea arvensis Lamarck.