Around March, ‘shamrock’ plants are sold in grocery stores, discount stores and floral shops as a decoration for St. Patrick’s Day. These plants, unrelated to clovers, are a type of Oxalis, (also known as wood sorrels). The clover shaped leaves come in shades of green, red, or purple, and can fold up at night or on overcast days. The five-petaled flowers, borne on long stalks, can be white, yellow, pink or red.
When selecting oxalis plants for a seasonal decoration, choose those with lush, healthy foliage and many new flower buds. All Oxalis species need cool conditions, especially when in bloom, and bright light to thrive indoors. A bright sunny window where the temperature is no greater than 75ºF during the day and 15-25 degrees cooler at night is a good location. Keep the soil barely moist, but not wet. Most types can tolerate slight drying between watering. Fertilize monthly when plants are actively growing. Oxalis have few pests, but aphids or whiteflies may occasionally be a problem.
The plants will start to decline after a few months, usually during the summer. Instead of throwing the pot out, allow the plants to go dormant. When the leaves start to die back, stop watering and allow the leaves to dry out and turn brown. Remove the dead leaves and place the container in a cool, dark spot for 2-3 months (except the purple-leaf types, which only require about a month’s dormancy).
After this enforced rest period, move the container back to the bright window and begin watering again and fertilize or repot before returning the bulbs to the sunny window. Place them just under the soil surface in a well-drained soilless medium. New growth should begin to appear soon thereafter. Oxalis are easy to propagate when dormant by dividing the many small bulbs. The bulbs separate easily and can be potted up in small groups.
For more information about other houseplants, visit https://extension.umn.edu/find-plants/houseplants