Wood Sorrel, Purple Shamrock & relatives · 1 genus covered
Oxalis is one of the most consistently misunderstood houseplant genera, primarily because of its dormancy cycle. A plant growing vigorously through spring will abruptly yellow and collapse in late summer, looking completely dead. It is not. The bulbs are alive underground, resting. Growers who discard a dormant Oxalis lose the bulbs and then buy the same plant again the following year, confused by the pattern. The dormancy is normal, expected, and manageable: reduce water as leaves yellow, stop almost entirely once growth ceases, rest for four to eight weeks in a cool dark spot, and resume watering when new growth appears. The other signature characteristic is nyctinastic movement: leaves and flowers fold closed at night and in low light, reopening with the morning, driven by turgor pressure changes in response to light. Of the commonly grown species, triangularis is the most widely available and the most striking, with deep purple three-lobed leaves that darken further in bright light.
The most widely grown ornamental Oxalis. Deep burgundy-purple, three-lobed leaves that fold closed at night and in low light, reopening with the morning light. Small pink-purple flowers. The purple coloration is most intense in bright indirect light. In lower light the leaves become a duller, greener purple. One of the most visually distinctive small houseplants available. The dormancy cycle (typically late summer to early autumn) is the primary source of confusion: when leaves yellow and the plant collapses, this is normal. Reduce and then stop watering, rest the bulbs in a cool dark position for four to eight weeks, and resume watering when new growth appears at the surface.
Detailed CareA selected form of triangularis with particularly vivid purple coloration and strong flower production. Near-identical to the standard species in appearance and behavior. The distinction is the intensity and consistency of the purple. Same care in every respect, same dormancy cycle. A good choice when a reliable deep-purple form is wanted.
ToxicityFour-lobed green leaves with a distinctive dark purple-brown marking at the center of each lobe, forming a cross pattern across the leaf. Red-pink flowers in clusters. More cold-tolerant than triangularis and handles cool, bright positions that would stress other Oxalis. The cross pattern is the most graphically striking of the common Oxalis leaf forms. Same dormancy cycle applies. Slightly more forgiving than triangularis in terms of light flexibility.
ToxicityUnusual spiraling leaf arrangement with bronze-green leaves that have a warm, velvet-like quality in good light. Less widely available than triangularis. More architectural in habit. The spiral growth gives it a distinctly different character from the round-leafed species. Requires medium indirect light to maintain the bronze coloration. Same dormancy cycle as all Oxalis.
ToxicitySmall, green three-lobed leaves with delicate pink flowers. More compact than triangularis. More tolerant of lower light conditions than the purple species — useful for positions where triangularis would become leggy. Good for terrariums where the small scale works well. The same dormancy cycle applies, though it may be less pronounced in consistently warm, well-lit terrarium conditions.
Toxicity