Grona heterocarpos subsp. ovalifolia (Prain) H.Ohashi & K.Ohashi

Global description

Grona heterocarpos subsp. ovalifolia is a highly branched, prostrate species forming large, dense patches. It roots very easily at the nodes in contact with the soil. The stem is cylindrical, often tinged with red, finely pubescent. The leaves are alternate, compound but usually unifoliolate, borne on a long petiole that is slightly enlarged at the base. The stipules are narrow and long, triangular at the base and long acuminate at the top. The blade of the terminal leaflet is very short-petiolulate with two small, filiform stipels. The leaf blade is subcoriaceous, long-oval, with a rounded base and a rounded, mucronate apex. The upper face is glabrous and the lower face finely pubescent. Inflorescence in dense, subsessile, terminal or axillary racemes of pink and red papilionaceous flowers. The fruit is a dehiscent pod with 5-7 rectangular articles covered with hooked hairs.

General habit

Grona heterocarpos subsp. ovalifolia is a herbaceous species or subshrub, subwoody at the base, growing in large dense patches from creeping stems, profusely branched at the base and rapidly radicating.

Underground system

The main root is taproot, but numerous secondary roots develop at the nodes in contact with the soil.

Stem

The stem is cylindrical, solid, very often red in colour. The older parts are subglabrous while the younger parts are finely pubescent with white appressed hairs. It is spread out on the ground and can be 30 to 150 cm long.

Leaf

The leaves are alternate, compound, mostly unifoliolate, with only the terminal leaflet (giving the impression of simple leaves), sometimes trifoliolate towards the end of the stems. They are borne on a 1 to 2 cm long, often red, pubescent petiole with white appressed hairs, slightly gutter-shaped and enlarged at the base. The stipules are long and narrow, triangular at the base and long acuminate at the top. They are 0.5 to 1 cm long and 2 mm wide at the base. They are red in colour and finely pubescent. The terminal leaflet and the lateral leaflets, when present, are borne by a very short petiolule, 2 mm long, framed by two filiform stipels, 2 to 2.5 mm long. The terminal leaflet has a subcoriaceous, long-oval, broadly elliptic or long-obovate blade, 3.5 to 6 cm long and 3 to 4 cm wide. The lateral leaflets, when present, are distinctly smaller, rather elliptical in shape, 2 cm long and 1 cm wide. The base is broadly rounded and the apex more narrowly rounded, mucronate and sometimes more or less emarginate. The margin is entire. The upper face is glabrous, dark green, showing a network of 5 to 8 pairs of pinnate secondary veins, joining near the margin, without reaching the margin. The underside is glaucous green with pubescence, especially along the midrib. The secondary and tertiary veins are prominent on the underside. The midrib and margin are sometimes tinged with red.

Inflorescence

The inflorescence is a 2.5-7 cm long terminal or axillary racem with a densely pubescent rachis, with a mixture of straight appressed hairs and hooked hairs, white or yellow.

Flowers

The flowers are solitary, borne on a glabrous pedicel 2 to 4 mm long, with a lanceolate oval bract at its base, acuminate at the top and rapidly deciduous. The calyx is campanulate, glabrous, 1.5 to 2 mm long, ending in 4 triangular lobes more than 1/2 the length of the calyx. The upper lobes are bifid at the top. The corolla is papilionaceous, 5 to 6 mm long. The standard is 2-lobed, subcircular, pink and the wings are narrowly obovate, red to very dark pink. The stamen cluster is diadelphic (1 free stamen).

Fruit

The fruit is a flat pod, 12-20 mm long and 2.5-3 mm wide, with 4-7 quadrangular or slightly rectangular articles, the upper suture is straight and the lower suture slightly scalloped, dehiscent. The pod is covered with hooked hairs.

Seed

The seed is kidney-shaped, 2 mm long and 1.5 mm wide.

Origin

Grona heterocarpos subsp. ovalifolia is native to South East Asia (South East China, Vietnam, Laos, Burma, Malaysia, Thailand, Borneo, Java, Sumatra).

Worldwide distribution

This species was introduced in French Guiana as a fodder plant and is now naturalized. Also introduced as a fodder plant in the West Indies under the var. heterocarpum.

https://www.gbif.org/species/10739446