While green carnations are all the rage on St. Patrick’s Day, I would rather give a shamrock plant to a loved one. Oxalis, or the shamrock plant, can be an invasive weed in warm climates, a sour-tasting ground cover in cold climates or a cute houseplant. I want to focus on the houseplant versions.
First of all, oxalis may be called the shamrock plant, but it's not related to true shamrocks. True shamrocks are in the Trifolium or clover family.
Oxalis has a number of colorful new varieties on the market. The Proven Winners Charmed Series features Wine with purple leaves and white flowers, Molten Lava with chartreuse foliage and yellow flowers, and Zinfandel with wine red leaves and yellow flowers. Iron Cross has green leaves with a burgundy cross in the center and pink flowers.
Many try growing oxalis as houseplants and end up tossing them because they look ratty. The key to success is to be merciless. Grow oxalis in a sunny window now and move them into a part-shade location for summer. Then oxalis needs a dormant period in late fall and early winter.
Before winter, cut them back to the soil line, stop watering and store them in a dark, cool room for a few months. Bring them out now and they will grow better with the longer, warmer days.
Oxalis also can become insect infested indoors. Cut them back if that occurs and repot them. They will regrow from their tiny bulbs. Oh, and oxalis leaves can be poisonous to pets if eaten in large quantities.