Oxalis corniculata (Amrul):

A Comprehensive Botanical and Ecological Account of a Resilient Herb

Oxalis corniculata, commonly known as Amrul in eastern India, is a small yet remarkably adaptable herbaceous plant belonging to the family Oxalidaceae. Despite its modest appearance, the species occupies a wide ecological niche and is recognized for its persistence across disturbed landscapes, agricultural fields, forest edges, and coastal plains. Its ability to thrive under varying moisture, soil, and light conditions has allowed it to establish a nearly cosmopolitan distribution.

In the lower Gangetic delta and the peripheries of the Sundarbans, Oxalis corniculata is a familiar component of ground-level vegetation. It often appears spontaneously in homesteads, pathways, embankments, and fallow lands, reflecting both ecological resilience and close association with human-modified habitats. This article presents a detailed scientific overview of the species, addressing its taxonomy, morphology, habitat preferences, ecological functions, and conservation context, with particular reference to the Sundarbans region.

Taxonomy & Classification

Oxalis corniculata is a member of the genus Oxalis, which comprises a large and diverse group of herbaceous plants commonly referred to as wood sorrels. The genus is characterized by trifoliate leaves and the presence of oxalic acid, which imparts a sour taste to the foliage.

• Kingdom: Plantae
• Clade: Angiosperms
• Clade: Eudicots
• Order: Oxalidales
• Family: Oxalidaceae
• Genus: Oxalis
• Species: Oxalis corniculata

The species name corniculata refers to the horn-like shape of its elongated fruiting capsules. Taxonomically, the species is notable for its morphological plasticity, which has historically led to confusion with closely related taxa.

Morphology & Field Identification

Oxalis corniculata is a low-growing, creeping perennial or annual herb, often forming dense mats close to the ground. Its distinctive leaf shape and bright yellow flowers make it easily recognizable in the field.

Stem and Growth Habit

The stems are slender, prostrate, and extensively branched, often rooting at the nodes upon contact with moist soil. This creeping habit allows rapid lateral spread and contributes to the plant’s success in disturbed environments. Stems may appear green, reddish, or purplish depending on light exposure.

Leaves

Leaves are trifoliate, with each leaflet heart-shaped and measuring 1–2 cm in length. The leaflets fold inward at night or under low light conditions, a phenomenon known as nyctinasty. The foliage is typically green but may develop a purplish tint under stress.

Flowers and Fruits

Flowers are small, solitary, and axillary, with five bright yellow petals. Flowering occurs throughout much of the year under favorable conditions. The fruit is a narrow, cylindrical capsule that dehisces explosively when mature, dispersing seeds over short distances.

Habitat & Distribution

Oxalis corniculata demonstrates exceptional ecological flexibility, inhabiting a wide range of natural and semi-natural environments. Its success is largely attributed to its rapid growth, vegetative propagation, and efficient seed dispersal mechanisms.

Global Range

The species is distributed across tropical, subtropical, and temperate regions worldwide. It occurs naturally or as a naturalized species in Asia, Africa, Europe, the Americas, and Oceania. Its global presence reflects both natural dispersal and unintentional spread through human activity.

Preferred Habitat

Preferred habitats include moist lawns, garden beds, roadsides, agricultural margins, forest clearings, and riverbanks. The plant thrives in well-drained soils but tolerates compaction, moderate salinity, and fluctuating moisture levels.

Occurrence

In India, Oxalis corniculata is one of the most commonly encountered herbaceous plants, present in both rural and urban landscapes. It occurs year-round in regions with adequate moisture and appears rapidly after rainfall in drier zones.

Preferred Habitat in the Sundarbans Region

Within the Sundarbans and its adjoining areas, Oxalis corniculata is predominantly found in village courtyards, embankments, canal edges, forest fringes, and reclaimed agricultural lands. While it does not occur within core mangrove forests, it flourishes in buffer zones influenced by freshwater input.

The species tolerates slightly saline soils and high humidity, making it well suited to deltaic environments with fluctuating hydrological conditions.

Ecological Role

Oxalis corniculata plays a multifaceted ecological role despite its small size. As a ground-covering species, it helps reduce soil erosion, particularly during monsoon rains. Its creeping growth stabilizes exposed soil surfaces in disturbed areas.

The flowers attract a variety of small pollinators, while the plant contributes organic matter to the soil through rapid biomass turnover. Its presence also supports microfaunal communities within the soil layer.

Habitat Alteration

Although Oxalis corniculata is resilient, extreme habitat alteration can influence its distribution. Intensive land paving, excessive herbicide use, and prolonged flooding may locally suppress populations.

In coastal delta regions, increasing soil salinity and changes in freshwater availability may alter competitive interactions with other herbaceous species.

Conservation Efforts

Oxalis corniculata is not currently considered threatened due to its widespread distribution and adaptive capacity. However, conserving diverse ground flora remains important for maintaining ecological balance.

In the Sundarbans region, sustainable land-use practices and preservation of semi-natural habitats indirectly support the continued presence of this species.

Did You Know?

• The leaves of Oxalis corniculata exhibit night-time folding behavior.
• The plant disperses its seeds through explosive fruit dehiscence.
• It is often one of the first plants to colonize disturbed soil.
• The sour taste of the leaves is due to the presence of oxalic acid.

External Reference

For detailed botanical classification and additional information, consult the relevant entry on Wikipedia.