Oxalis corniculata
Found creeping along the Lowland Meadow floor with clover-like trifoliate leaves and small yellow flowers, this pantropical weed self-colonized the system in April 2025 and spreads by explosive seed capsules and node-rooting stems.
A pantropical weed that self-colonized the Lowland Meadow in April 2025, initially mistaken for clover by the observer; its trifoliate heart-shaped leaves, yellow flowers, and creeping ground-hugging habit are characteristic of Oxalis corniculata, one of the most widespread small weeds in the world.
Oxalis corniculata is a small annual or perennial herb in the wood sorrel family (Oxalidaceae). It is one of the most widely distributed weed species in the world, found across tropical, subtropical, and warm temperate regions on every inhabited continent. In South Florida, it is a ubiquitous volunteer in lawns, garden beds, sidewalk cracks, potted plants, and any moist disturbed soil with adequate light.
The plant grows low to the ground with slender creeping stems that root at the nodes as they spread. Leaves are compound, with three heart-shaped (obcordate) leaflets on a long petiole, resembling clover in general outline but without the white chevron markings characteristic of white Dutch clover. Flowers are small, five-petaled, and yellow. Pigmentation varies: high-light plants tend toward reddish-purple tints in the stems and leaf undersides, while shaded plants remain green throughout.
All parts of the plant accumulate oxalic acid, giving the leaves, stems, and flowers a distinctly sour taste and making "sourgrass" a widely used common name. The oxalic acid is not harmful in incidental quantities but can be problematic for animals that graze heavily on the plant.
O. corniculata displays nyctinasty: the leaflets fold downward at night and reopen in daylight. The same folding response occurs when the plant is touched or exposed to intense heat. This movement is driven by turgor pressure changes at the base of each leaflet and is visible without magnification.
The plant reproduces primarily by seed. Each ripe seed capsule is torpedo-shaped and explosively ejects its seeds when touched, a mechanism called ballistic seed dispersal; seeds scatter several centimeters to a meter from the parent plant. The plant also spreads vegetatively via the creeping, node-rooting stems. Seeds are persistent in the soil and can germinate over an extended period after dispersal.
In natural and garden settings, O. corniculata is primarily a competitor for light and soil space in disturbed substrates. It functions as a low-growing photosynthetic primary producer; fallen leaves and stem material contribute to the detrital base. It is grazed by a range of generalist invertebrate herbivores. In miniBIOTA's Lowland Meadow, the plant self-colonized a closed terrestrial substrate and functions as a small-scale ground-cover producer on the meadow floor.
In the Lowland Meadow, Creeping Woodsorrel functions as a low-growing photosynthetic producer and ground-cover plant on the meadow floor. Its modest size and creeping habit place it in the understory plant layer beneath taller grasses and herbs. Fallen leaves, stem fragments, and seed capsules contribute to the detrital base accessible to soil detritivores including Earthworm and Springtail. The explosive seed dispersal mechanism allows rapid local spread from a single founding plant if substrate conditions remain favorable.
Not deliberately introduced. Oxalis corniculata is a pantropical weed that routinely self-colonizes any moist disturbed soil with adequate light. Entry into miniBIOTA probably occurred via windblown seed or in soil or potting mix associated with another plant introduction. The April 6, 2025 observation is the first and only documented record.
April 6, 2025: Creeping Woodsorrel observed growing spontaneously in the Lowland Meadow; observer initially mistook it for clover. Self-colonized; not deliberately introduced. No subsequent observation has been recorded. Current presence and population size are unknown.
Photosynthetic primary producer in the Lowland Meadow. As a small ground-cover plant, its contribution to total primary production is modest, but fallen leaves and stem material contribute to the detrital base available to soil detritivores including Earthworm and Springtail. Leaves contain oxalic acid, which may deter some generalist grazers.
One of the most environmentally tolerant weeds in the world; thrives in moist disturbed soils across a wide range of temperature, light, and pH conditions. In miniBIOTA's Lowland Meadow, the principal constraint would be substrate moisture; the plant will establish in any patch of moist soil with adequate light. No miniBIOTA-specific tolerance measurements on record.
No reproductive events documented in miniBIOTA. Oxalis corniculata produces ripe seed capsules that explosively eject seeds when touched or disturbed, allowing rapid local spread. The plant also roots at stem nodes as stems creep along the substrate surface. Both mechanisms can establish new individuals from a single founding plant.
No ecological interactions involving Creeping Woodsorrel have been documented in miniBIOTA beyond the April 2025 observation. If present, it provides detrital input to soil detritivores and possible browsing material for terrestrial herbivores.
Follow this species across the habitats where it currently appears in the miniBIOTA biosphere.
