Old World Diamond-Flower / Carpet-weed (Note: This is a broadleaf plant, not a true grass)
Oldenlandia corymbosa (syn. Hedyotis corymbosa) · Warm-season, Annual, C3 Dicot (broadleaf weed)
Grass Family
Rubiaceae (Coffee family), not Poaceae
Grass Category
Invasive/Weed, Wetland/Riparian plant, lawn competitor
Variety / Cultivar
Common wild type
Hardiness Zones
USDA Zones 8-11; frost-sensitive annual; thrives in heat and monsoon-like conditions.
About This Grass
A low-growing, sprawling herbaceous plant with square-ish green stems. It forms a dense mat-like cover. It produces very small, four-petaled white or pale lavender flowers on slender stalks (corymbs) emerging from leaf axils.
Blade Characteristics
Leaves (not blades) are opposite, linear-oblong to narrowly elliptic, 0.5-1.5 inches long, sessile or nearly so; margins are flat or slightly revolute; distinct midrib; no ligule or auricles (stipules present instead).
Root System
Fine, shallow taproot with many fibrous lateral roots; efficient at colonizing damp, disturbed soils; fast establishment in moist areas.
Growing Information
Origin Region
Native to Africa and Asia; naturalized throughout the Americas and Southeast Asia in tropical/subtropical regions
Growth Habit
Prostrate, spreading, and many-branched herb; forms low mats; primary spread by seed and occasional rooting at nodes
Sunlight & Water Needs
Partial sun to full sun; prefers high moisture and humidity; thrives in muddy, heavy, or poorly drained soils; low drought tolerance.
Mowing & Maintenance
Usually managed as a weed; survives low mowing due to prostrate growth; can be controlled by improving drainage and using selective broadleaf herbicides.
Special Characteristics
Very high moisture tolerance; can survive short-term waterlogging; grows in gaps between paving stones and in bare patches of lawns.
Ecological Information
Introduced/Invasive in many regions; minimal wildlife value; acts as a pioneer species in disturbed, wet soils; often used in traditional herbal medicine in Asia.