Vermont Garden Journal: The Shamrock Imposter, Oxalis

Jan 12, 2018

Some may say that oxalis, or the shamrock plant, is an invasive weed, a sour-tasting groundcover or a cute houseplant. All three are correct. In warm climates, oxalis can be an attractive groundcover or a weed. In colder climates, yellow sorrel is an oxalis that grows as an understory plant in the forest. Then there's the tender houseplant versions. This is where oxalis becomes more interesting.

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 varieties including:

  • Wine:  purple leaves and white flowers
  • Molten Lava:  chartreuse foliage with yellow flowers
  • Zinfandel:  wine-red leaves and yellow flowers
  • Iron Cross:  green leaves with a burgundy cross in the center and pink flowers

These colorful oxalis make great annuals in a container, rock garden or flower border. You'll also see lots of them as houseplants in garden centers, but you'll need to be smart about growing them indoors. 

The key to success with indoor oxalis is to be merciless. It needs a dormant period in late fall and early winter. Before bringing your oxalis indoors for winter, cut back to the soil line, stop watering and store in a dark, cool room for a few months. Bring them out in late winter and they will grow better with longer, warmer days.

Oxalis can also become insect-infested. If that occurs, cut them back and repot. Also, the leaves can be poisonous to pets if eaten in large quantities.

Now for this week's tip:  low humidity in winter is rough on foliage houseplants. Remember to shower with your plants every so often to increase humidity levels and clean the leaves.