Asiatic Dayflower (New York City EcoFlora Volunteer Guide)

Asiatic Dayflower

Commelina communis

Summary ⁶

Commelina communis, commonly known as the Asiatic dayflower, is an herbaceous annual plant in the dayflower family. It gets its name because the blooms last for only one day. It is native throughout much of East Asia and northern parts of Southeast Asia. In China, the plant is known as yazhicao (simplified Chinese: 鸭跖草; traditional Chinese: 鴨跖草; pinyin: yāzhīcǎo), roughly translating to "duckfoot herb", while in Japan it is known as tsuyukusa (露草, tsuyukusa?), meaning "dew herb". It has also been introduced to parts of central and southeastern Europe and much of eastern North America, where it has spread to become a noxious weed. It is common in disturbed sites and in moist soil. The flowers emerge from summer through fall and are distinctive with two relatively large blue petals and one very reduced white petal.

At the Garden ⁷

Asiatic dayflower is a common weed, and has been known to occur along the Ridge Trail in the Thain Family Forest.

Description ⁸

The Asiatic dayflower is an annual herb with stems that are typically decumbent, meaning that they are prostrate at the base but become erect towards the tips, but some individuals may be simply erect. The diffusely branched stems tend to root at the basal nodes. The pubescence on the stems is variable, but common patterns include a line of hair continuous with the leaf sheath, or they may be glabrous basally, meaning hairless, and puberulent towards the extremities, that is covered with fine hairs. The leaves are sessile: they lack a leaf stalk, also known as a petiole; or they may be subpetiolate, meaning they have very small petioles. The leaf sheaths are cylindrical, sometimes striped with red, and typically glabrous, but usually have margins that are puberulent or pilose, meaning lined with fine, soft hairs. The leaf blades range from narrowly lanceolate, or lance-shaped, to ovate-elliptic, between egg-shaped and ellipse-shaped. They measure 3–12 cm (1 ¹⁄₄–4 ³⁄₄ in) by 1–4 cm (¹⁄₂–1 ¹⁄₂ in) wide. The blades range from glabrous to puberulent and have scabrescent, or slightly rough, margins. Their tips are acute, meaning they come to a point quickly, to acuminate, meaning the point develops gradually. The leaf bases are oblique, or uneven.

The flowers are arranged on inflorescences called cincinni (singular: cincinnus), which are also called scorpioid cymes. This is a form of a monochasium where the lateral branches arise alternately. The cincinni are subtended by a spathe, a modified leaf. The solitary spathes usually measure 1.2–3 cm (¹⁄₂–1 ¹⁄₄ in) long, but some may be up to 3.5 cm (1 ¹⁄₂ in) in length, while they are 0.8–1.3 cm (¹⁄₄–¹⁄₂ in) tall, but sometimes up to 1.8 cm (³⁄₄ in). The uncurved spathes typically have a cordate, or heart-shaped, whitish base, which contrasts with its dark green veins. Their margins lack hairs, are somewhat scabrous, or rough, and are unfused, meaning they are distinct to the base. Their apices are acute to acuminate while the surfaces are glabrous, puberulent, or hirsute-ciliate, meaning with longer, shaggier hairs. The spathes are borne on peduncles, or stalks, that measure 0.8–3.5 cm (¹⁄₄–1 ¹⁄₂ in) and sometimes up to 5 cm (2.0 in) long.

There are often two cincinni present, though the upper, or distal, cincinnus may be vestigial. The lower, or proximal, cincinnus bears 1 to 4 bisexual flowers and is nearly included in the spathe, while the upper cincinnus has 1 to 2 male flowers and is about 8 mm (0.31 in) long. The individual flowers are subtended by bracteoles that fall off early in development. The pedicels supporting single flowers, and later the fruits, are erect initially but curve when in fruit. They measure about 3–4 mm (0.12–0.16 in). The 3 concave, membranous sepals are inconspicuous, but persist after the fruit develops; the lateral pair are fused basally, measure only 4.5–5 mm (0.18–0.20 in) long by 3–3.7 mm (0.12–0.15 in) wide, and are elliptic and glabrous. The lower sepal is lanceolate and about 4.5 mm (0.18 in) long by about 2.2 mm (0.087 in) wide. The 2 upper petals are blue to indigo in colour, while the much smaller lower petal is white. The upper two petals measure 9–10 mm (0.35–0.39 in) long by 8–10 mm (0.31–0.39 in) wide, while the lower petal is 5–6 mm (0.20–0.24 in) long by about 6 mm (0.24 in) wide. The 2 upper petals are composed of a claw about 3 mm (0.12 in) long and a broadly ovate limb with an acute apex and a cuneate-cordate base.

There are three anticous fertile stamens, meaning they are on the lower part of the flower, and three posticous infertile stamens, meaning they are on the upper part of the flower. These infertile stamens are termed staminodes. The fertile stamens are dimorphic: the lateral pair have maroon to indigo anthers that measure about 2 mm (0.079 in) long and are elliptic with a base that is sagittate or arrowhead-shaped. Their filaments are about 10–12 mm (0.39–0.47 in) long. The central fertile stamen has a yellow, elliptic anther with a maroon connective and a base that is hastate or spearhead-shaped, but with the lobes at right angles. The anther measures about 2.5 mm (0.098 in) long while its filament is about 5–6 mm (0.20–0.24 in) long. The three staminodes are all alike with yellow, cruciform, or cross-shaped, antherodes that are about 2 mm (0.079 in) long on filaments about 3 mm (0.12 in) long. Sometimes the antherodes will have a central maroon spot. Each antherode has two abortive lateral pollen sacks. The ovary is ellipsoid, about 2 mm (0.079 in) long and has a style that is about 1.3 cm (0.51 in) long.

The fruit is a dehiscent, ellipsoid capsule with two locules each containing two seeds. The capsule is glabrous, brown, measures 4.5–8 mm (0.18–0.31 in) long, and dehisces into two valves. The seeds are brown or brownish yellow in colour and deltoid, or roughly triangular in outline. They are dorsiventral, meaning they have distinct upper and lower surfaces, with the ventral, or lower, surface being planar and the dorsal, or upper, surface being convex. Seeds range in length from 2.5–4.2 mm (0.098–0.165 in), but seeds as short as 2 mm (0.079 in) can occur, while they are 2.2–3 mm (0.087–0.118 in) across. The surfaces are rugose pitted-reticulate and are densely covered with smaller farinose granules with sparse larger farinose granules.

Distribution and habitat ⁸

The plant's native distribution includes much of East Asia and Southeast Asia. Country by country, it is found in China, Taiwan, Japan, Korea, the Russian Far East, Cambodia, Laos, Malaysia, Thailand and Vietnam. Within China it is found in all provinces except Qinghai, Hainan, Xinjiang, and Tibet. In Japan the plant is found throughout the bulk of the country from Hokkaido south to Kyūshū. In Russia the Asiatic dayflower is found naturally on Sakhalin as well as in the Far East in areas surrounding the Ussuri River.

The species has been introduced to much of Europe and eastern North America. On the former continent it is now found from Central Europe well into western Russia. Specifically it is known from Italy north to Switzerland, east through the region encompassing the former Yugoslavia, east into the regions around the Black Sea including Romania, the Moldavia Region, and Ukraine but excluding Crimea, north through the Dnieper Basin into Belarus and Russia, continuing east into the regions surrounding the Don River and the Volga River south to their intersection at the Volga-Don Canal and north to the regions around Lake Ladoga and Lake Ilmen, and farther east to the regions of the Ural River and the Kama River. It is also found in the Czech Republic and Slovakia. It is present in the provinces of Ontario and Quebec in Canada, and in most of the eastern and central American states from Massachusetts and New York in the northeast, west to Minnesota and south through the Great Plains to Texas and east to extreme northern Florida in the United States.

Within its native distribution, the plant is most typical of moist, open places, including shady forest edges and wet areas of crop fields, orchards, ditches, and roadsides. In Taiwan, it can be found from 350 to 2,400 m (1,150 to 7,870 ft) elevation. In areas where the Asiatic dayflower is an introduced weed it is most common in waste places, but also along the edges of fields, woods, and marshes, and occasionally penetrating into woods.

Sources and Credits

(c) TANAKA Juuyoh (ç”°ä¸åæ´‹), some rights reserved (CC BY), http://www.flickr.com/photos/13910409@N05/2591233784
(c) D.J. McNeil, some rights reserved (CC BY-NC), uploaded by D.J. McNeil
(c) Carrie Seltzer, some rights reserved (CC BY-NC), uploaded by Carrie Seltzer
(c) Tim Hite, some rights reserved (CC BY), uploaded by Tim Hite
(c) Susan J. Hewitt, some rights reserved (CC BY-NC), uploaded by Susan J. Hewitt
(c) Wikipedia, some rights reserved (CC BY-SA), http://en.wikipedia.org/wiki/Commelina_communis
(c) bkmertz, some rights reserved (CC BY-SA)
Adapted by bkmertz from a work by (c) Wikipedia, some rights reserved (CC BY-SA), http://en.wikipedia.org/wiki/Commelina_communis

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