Cardamine occulta
Hornem.Annual herb to 40 cm high with a fibrous root system; flowering stems erect or decumbent and rooting at nodes, largely glabrous throughout. Leaves glabrous on upper surface, sometimes ciliate along margins; basal leaves few, not forming a rosette or persisting; cauline leaves (2–)4–7, larger than basal leaves, (1.5–)3–7 cm long, pinnate or pinnately lobed with (2–)3–4 pairs of lateral pinnae, terminal pinna larger, often 3-lobed. Racemes few–many-flowered; sepals 1.3–2 mm long, occasionally with a few hairs; petals c. 3 mm long, white; mature style to c. 1 mm long. Fruits inclined at 45°–90° to a flexuose rachis, not or hardly overtopping open flowers of the same inflorescence, 1.5–2.3 cm long, 1.0–1.5 mm wide; pedicles 3–8 mm long; seeds c. 0.8–1.0 mm long. Flowers mostly Jul.–Feb.
VVP, VRiv, MuF, GipP, EGL, HSF, Strz. Also in WA, NSW. Probably native to Eastern Asia. Naturalised in Canada, Europe, Mexico, and USA. Collected from urban areas, particularly inner suburbs of Melbourne (but also Bundoora, Orbost, Echuca and Numurkah areas), growing in nurseries, cracks in pavement, garden beds and on wet mud in artificial lakes and ponds.
Marhold et al. (2016) have established that the correct name for the plants previously known as Cardamine aff. flexuosa sensu Fl. Victoria 3:435 (1996) is Cardamine occulta. Cardamine occulta is readily distinguishable from typical C. flexuosa, C. hirsuta and C. corymbosa (which also grow in urban environments), by the absence of scattered hairs on the upper leaf surface. It also also differs in not forming a distinct rosette—only a few basal leaves develop and these are not persistent. Well-developed specimens produce long, secondary branches from the base and leaf axils of the primary flowering stem. Although sometimes apparently glabrous, close inspection generally reveals the presence of hairs on flower buds and young axillary shoots. These hairs are never present in otherwise similar native species, notably C. moirensis.
Marhold, K.; Slenker, M.; Kudoh, H.; Zozomova-Lihova, J. (2016). Cardamine occulta, the correct species name for invasive Asian plants previously classified as C. flexuosa, and its occurrence in Europe. PhytoKeys 62: 57–72.
