How to Grow Oxalis
You can’t miss it in the garden center. The deep maroon – almost black – foliage of purple Oxalis pops against all the other greenery in the houseplant section, making it a favorite with shoppers.
Oxalis often is mistakenly referred to as a shamrock or lucky four-leaf clover – and with good reason. In Ireland, four different species of Oxalis – the largest genus in the wood-sorrel family – are commonly associated with good luck. But its American cousins, especially the four-leafed Oxalis tretraphylla, are popular both indoors and out for their easy care.
While some species of Oxalis are invasive weeds that wreak havoc with lawns, such as Bermuda buttercup (O. pes-caprae) and creeping wood-sorrel (O. corniculata), these showier versions are hardy to zone 5. They include the rosy-flowered O. depressa and the pink sorrel (O. tretraphylla), often erroneously sold as “four-leaf clover.”
The mounding plants grow 6 to 12 inches tall and sport eye-catching shamrock-shaped leaflets ranging from chartreuse to dark maroon and multiple combinations in between, including ones with speckles.
Perhaps the most popular these days is the purple oxalis, O. triangularis, commonly called purple shamrock. A native of Brazil, it features dark purple triangular leaflets that close at night.
This oxalis prefers light shade and moist, well-drained soil. Indoors, give it bright light and cool temperatures (60 to 70 degrees) – the brighter the light, the more vibrant the foliage and flowers – but avoid extremes. Feed it a regular houseplant fertilizer.
Here’s hoping for the luck of the Irish – even though the plant’s from Brazil!