Oxalis deppei, commonly known as the shamrock plant or lucky clover plant, appears in stores before Saint Patrick's Day. These plants get their common name from their leaves' clover-like appearance. Shamrock plants differ from clover, however, as their leaves close at night and they produce tubular white, pink, lavender or red flowers in spring. Shamrock plants make excellent houseplants, although they should be allowed to go dormant several times a year. They can be successfully grown outside in rock gardens or containers. You can choose plants with purple, green or variegated foliage.
Growing Oxalis Plants Indoors
Choose firm rhizomes with three to five "eyes" or buds.
Fill the container you will be using with general-purpose potting soil. Any size or shape container will work--it just has to be big enough to hold the rhizome.
Remove the soil from the container and add enough horticulture sand to equal one-quarter the total volume of soil. Mix the soil and sand together. Adding sand gives you a faster-draining potting medium while still allowing the soil to hold water. Refill the pot with the potting mix.
Bury the Oxalis rhizome in the mix. The rhizome should barely be covered by soil. You don't want to see the rhizome but you don't want it covered with more than a 1/4 inch of soil.
Keep your shamrock plant moist but not soggy. Allow the surface of the soil to dry slightly before watering.
Place your shamrock plant in bright indirect light.
Allow your oxalis to go dormant two or three times a year. When the leaves and stems start to turn yellow, stop watering the plant, move it to a cool, dark room and allow the plant to die back to the rhizome. Remove the dead leaves and stems. Purple-leafed shamrocks will only need one to two months of dormancy; green-leafed shamrocks will need two to three months.
Bring your shamrock plant back into bright indirect light after its period of dormancy. Water as usual. Fertilize with a 10-10-10 commercial or organic houseplant fertilizer according to package directions. You should see new growth in one to three weeks.
Re-pot your shamrock in fresh soil once a year. It is easiest to re-pot just after a dormancy period before new growth starts. Replace all of the soil in the container using the soil/sand mix. Thoroughly wash the container or use a new one.
Planting Oxalis Outside
Plant Oxalis bulbs outside in early spring.
Choose a location that receives four to six hours of sunlight a day. The soil should be well-drained with a pH of 4.0 to 5.0. Afternoon shade works best for Oxalis in all areas of the United States.
Dig a hole twice as wide and deep as the rhizome.
Place the rhizome in the hole and cover it with 2 to 3 inches of soil.
Allow the top 1/2 inch to 1 inch of soil around the shamrock plants to dry before watering.
Fertilize your shamrock plants when they start to produce flowers, usually in late spring early summer, with a 10-10-10 commercial or organic fertilizer. Fertilize again when the plant stops flowering.
Lift Oxalis rhizomes in the fall after the plant has died back. Brush off as much soil as possible. Wrap each rhizome in paper towels and store them in a dark, dry, cool room.