Centella cordifolia, commonly known as swamp pennywort or arthritis herb,[2] is a trailing perennialherb[3] native to Australia.[4] The species is common in preferred local environments.[5][6] It potentially has medicinal purposes and indigenous cultural significance.[7]C. cordifolia can be sourced commercially at Australian plant nurseries.[5]
Description
Centella cordifolia is a groundcover herb that can grow up to 15 cm (5.9 in) tall,[4] and typically stretches 1–2 m (3 ft 3 in – 6 ft 7 in) wide.[5]
Leaves are heart-shaped (cordate), glabrescent, glossy and dark green.[4] The lamina is 1–3 cm (0.39–1.18 in) in length (with a similarly sized width), with five to seven veins and scarious margins.[8] When exposed directly to the sun, the leaves sit lowered, towards the ground, whereas in the shade they will stand upright.[4] The petiole has a purple tint, sheathing and broad at the base, and can be up to five times the length of the lamina.[8]
Flowers occur in subsessile umbels in an ovate shape, 3 mm (0.12 in) in length and each containing two to three florets.[8] Petals are purple or white,[5] ovate, and approximately 1.5 mm (0.059 in) in length.[8] Sepals form a very small, lobed ring, and at the base are two involucral bracts.[8] Anthers are dark purple.[8] Flowering times for C. cordifolia occur between late summer (December) to early autumn (March).[8][9]
Fruit is small, rounded, laterally compressed and contains seeds.[9] five longitudinal ribs span the mericarp,[8] which is 2.5–3 mm (0.098–0.118 in) in length and 4–5 mm (0.16–0.20 in) in width.[8] Small hairs towards the apex can be present, but in general the fruit is glabrous.[8]
Distinguishing C. cordifolia from other Centella species can be difficult, particularly from C. asiatica, which also inhabits parts of Australia.[10] The leaf margins of C. cordifolia are more serrate, whereas C. asiatica have more dentate margins.[10]C. cordifolia also has mat-like growth habit, which can be distinguished from other Centella species that have greater vertical and spreading growth habits.[10]
The herb grows in damp, poorly drained environments, including marshy soils or shallow waters.[5] Sun exposure can range from full to partial shade.[5] It is intolerant to phosphorus and moderately frost tolerant.[11]
Ecological processes
Centella cordifolia forms part of the understory in the various damp environments it inhabits.[11] It can provide a habitat for frogs.[7] Its root system stabilizes the damp soils it can grow in, preventing erosion.[12]
Medicinal and cultural significance
Centella cordifolia is known to treat rheumatism and arthritis,[7][2] though widespread adoption and evidence for this is limited. The herb is said to have an indigenous cultural significance,[7] again with limited information available.
