Oldenlandia

Scientific name

Oldenlandia L.

Common names

starviolet

Family

Rubiaceae

Similar genera

Bacopa, Boltonia, Dentella, Diodia, Justicia, Veronica

Native distribution

South America

Species cultivated

Oldenlandia salzmannii (DC.) Benth. & Hook.f. ex B.D. Jacks.

Adventive distribution

Oldenlandia lancifolia (Schumach.) DC. is introduced into South America, Central America, West Indies and Mexico.

O. salzmannii is introduced into the southeastern United States (AL, FL).

Weed status

not weedy

Habit

creeping herb; terrestrialterrestrial:
(adj) growing on land as opposed to living in water
, emergentemergent:
(adj) (syn. emersed) with parts raised out of the water; extending up out of the water
or submergedsubmerged:
(adj) (syn. submersed) under water; submerged below the water surface
for short periods

Brief description

Stem creeping to slightly ascending, filiformfiliform:
(adj) thread-like; long and thin
, faintly squarish, sparsely branched usually from the base, glabrousglabrous:
(adj) without hairs or scales
; rooting at lower nodes. Leaves oppositeopposite:
(adj) (of leaves) two leaves per node; in pairs on opposite sides of an axis
, decussatedecussate:
(adj) arranged along stem in pairs, with each pair at right angles to the pairs above and below
; petiolepetiole:
(n) the stalk of a leaf
flattened, lower half united to stipules; stipules minute, thin; leaf bladeblade:
(n) (syn. lamina) the flat, expanded part of a leaf, frond, or petal (excluding, e.g., the petiole)
narrowly to broadly elliptic; marginmargin:
(n) edge; rim
entireentire:
(adj) having a continuous margin that is not toothed or lobed
or usually with several trichome-like setae of varied lengths, giving the marginmargin:
(n) edge; rim
a lobedlobed:
(adj) divided into (usually rounded) segments
appearance if short and blunt; venationvenation:
(n) the arrangement of veins in a leaf
obscure, midribmidrib:
(n) the main or central vein, line or rib in a leaf or perianth segment
only. Flowers in leaf axils, solitary or 2 per node; pedicelspedicels:
(n) the stalk of a single flower in an inflorescence, or of a grass spikelet
straight or somewhat curved; sepals 4, fused, lobes ovateovate:
(adj) egg-shaped in outline; generally with the broad end at or near the base
, apexapex:
(n) the point farthest from the point of attachment; the tip (often pointed)
acuteacute:
(adj) tapering to a sharp, pointed apex with more or less straight sides; broader than acuminate; forming an angle of less than 90 degrees
; corollacorolla:
(n) the inner whorl(s) of the perianth; all the petals of a flower
campanulatecampanulate:
(adj) bell-shaped
, 4-lobed, lobes ovateovate:
(adj) egg-shaped in outline; generally with the broad end at or near the base
, apexapex:
(n) the point farthest from the point of attachment; the tip (often pointed)
± acuteacute:
(adj) tapering to a sharp, pointed apex with more or less straight sides; broader than acuminate; forming an angle of less than 90 degrees
, externally glabrousglabrous:
(adj) without hairs or scales
, internally hairy; white to pinkish.

Natural habitat

wet soil and shallow water, amphibiousamphibious:
(adj) of a plant able to live on land or in water
to emergent

Additional comments

Within this genus of nearly 250 species, here we focus solely on the aquatic species Oldenlandia salzmannii. It is often referred to and offered under the synonym Hedyotis salzmannii.

Oldenlandia was often treated as a subgenus of Hedyotis, later being recognized as a distinct genus due to chromosome and pollen data (Lewis, 1965). Although acknowledged as separate genera, an unequivocal phylogeny has yet to be published. A recent phylogenetic tree produced from limited molecular data still offers insight to the most probable placement of O. salzmannii. This poorly supported phylogeny demonstrates that O. salzmannii, although not nested within Oldenlandia, is more closely related to this genus than Hedyotis (Neupane et al, 2015). Further studies must be done but for now the accepted name in most flora, and the one we recognize here, is O. salzmannii.