The shamrock plant, or Oxalis regnellii, appears in stores around St. Patrick's Day, even though the plant isn't from Ireland at all, but hails from South America. Along with the traditional oxalis, with its green, triangular leaves and white flowers, you can usually find the purple-leaved shamrock (Oxalis triangulata) and four-leaved Iron Cross shamrock, with a dark cross at the center of each leaf (Oxalis tetraphylla). The shamrock is easy to grow as a houseplant as long as it receives bright light, as well as water when the soil surface becomes dry. It is normal for the leaves to fold up at night or on cloudy days. If cared for properly, the shamrock plant can live for several years.
Examine your shamrock plant. If the leaves are becoming dry and the stems are collapsing, the plant may be going dormant. This rest period usually begins in the fall, according to Gerald Klingaman of the University of Arkansas Extension.
Decrease the water you give to the plant. When the leaves are all dry, cut away the dried stems and place the pot in a cool, dark place until February.
Bring your shamrock plant back into a bright location in February. Begin watering the plant again. Apply a dose of liquid flowering-houseplant fertilizer according to label directions.
Place your shamrock plant outside for the summer in a cool, shady location.
Repot your shamrock if the bulbs fill the pot and the soil around them is compacted. However, as an oxalis likes to be tight in the pot in order to flower, it is best to repot infrequently.
Repot your shamrock plant when it is dormant. Lightly tap on the bottom of the pot to loosen the roots and the soil. The entire pot of oxalis may not come out in one piece and may separate around sections of the bulbs.
Choose a pot that is only one size larger than the pot the shamrock was in, or use smaller pots to plant sections of the bulbs. Place shards of a broken terra cotta pot or small pieces of gravel over the drainage holes of the new pots.
Fill the new pots with potting soil that is well-drained. The soil should be about 3/4 inch from the top of the pot if you will be planting the individual bulbs. If you are replanting the entire plant, fill the pot with 2 inches of soil and set the plant on the soil. Work the soil around the edges of the plant. Sections of bulbs or single bulbs should be just below the soil surface.
Water until water drains through the bottom of the pot. Place the shamrock in a bright window. In about three weeks, fertilize with the liquid flowering-houseplant fertilizer.
Diseases and Insect Problems
Examine the leaves of your oxalis plant. Diseases and insects can sap a plant's vigor and cause it to look unhealthy.
Notice if there is an orange substance on the undersides of the leaves. This could be a fungal disease called rust.
Remove any leaves afflicted with rust and dispose of them in the trash. According to The Gardener's Rake, a website dedicated to gardening, the leaves should be sprayed lightly with a mixture of dishwashing soap and water. Try to keep the leaves of the shamrock dry when you water the plant.
Check the leaves for any small, white spots and webbing among the leaves. The culprits may be spider mites. The Gardener's Rake recommends spraying the leaves with a mixture of water and dishwashing soap. Allow to sit on the leaves for an hour or so and then spray the mixture off with water.
Check for cultural problems. Leggy stems could mean the plant isn't receiving enough light. Bright yellow leaves signal an over-watering problem.