Oxalis stricta is a perennial herb to 50 cm tall, colonial from long thin, pale, succulent, rhizomes, branching and sending up new shoots, roots associated with VA mycorrhizas (Brundrett and Kendrick 1988); stem usually erect, hairy, some hairs septate, base of stem often reddish; no stipules.
Leaves alternate, 3-parted, leaflets heart-shaped, notched at tip, bright green, somewhat succulent, sour to taste, to 3 cm wide, leaf stalk unlobed. Leaves folded at midday and during night.
Flowers yellow, 5-parted, radially symmetrical, petals 0.4-0.9 cm long, self-fertile (autogamous), (Mulligan and Kevan 1973), inflorescence branched with oldest flower at top.
Fruit stalk horizontal or erect, not sharply bent downward; capsule 5-parted, green, ribbed, 0.8-1.5 cm long, hairs, if any, septate; seeds numerous, brown ridged; seeds eaten by birds and mammals.
Wetland status: UPL.
Frequency in NYC: Occasional.
Origin: Apparently native to North America.
Habitat: Open areas and part shade in disturbed soil, gardens, roadsides, trail edges.
Notes: Plants eaten by some mammals (Martin et al. 1951). Attacked by the maize rust fungus Puccinia sorghi and other species of Puccinia (Lovett-Doust et al. 1985). Very similar to O. dillenii, difficult to distinguish.