oxalis thumb Latin name: Oxalis corniculata or O. stricta (click here to distinguish between the two species, both commonly found in Oregon container nurseries).

Family:  Oxalidaceae

Common name: Yellow woodsorrel (O. stricta) or Creeping red sorrel (O. corniculata)
oxalis thumb
Life cycle:  perennial, spreads by seed, rhizome, or stolons
oxalis in pot Habit:  Small rounded clump, 4 - 8 inches tall and wide; O. corniculata grows low and more prostrate, while O. stricta is taller and more mounded.
leaf thumb
Foliage:  Palmately compound with 3 heart-shaped leaflets.  Reminiscent of 4-leaf clover.
oxalis flower
Flower:  Flowers are yellow with 5 petals and occur in an umbel (cluster).
oxalis seedpod
Seed or seedpods:  Long, thin, angular, and pubescent (more so for O. corniculata).
seedling thumb Cotyledon or seedling:  Cotyledons are small and round.  First true leaves are typical trifoliate and heart-shaped.
Roots:  Oxalis develop deep, thick taproots which make this weed difficult to hand pull from containers.

O. stricta spreads by rhizomes while O. corniculata spreads by stolons.
Control: View 2004 herbicide trials for controlling this and other common container weeds.
Look alikes: Clovers, black medic (Medicago lupulina).

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