Answer: Oxalis is a bulb-type plant with numerous species and varieties. Many have a "shamrock" shaped leaf, and they flower in many colors, including white, pink, purple and yellow. When they flower depends on the species. They take full sun or partial shade and prefer well-drained soil with consistent moisture. Oxalis should be dug and stored during the winter.
I found a description of a Oxalis regnellii var. triangularis that has "rich burgundy triangular leaves and soft pink flowers" in the Brent and Becky's Bulbs Catalogue for Summer 1999, (www.brentandbeckysbulbs.com) which sounds similar to what you have. I hope this info helps.
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