The oxalis bowiei, or wood sorrel plant, is often sold as a shamrock, lucky shamrock or Irish shamrock plant. Oxalis is not a true shamrock but simply looks quite a bit like the very difficult to grow true Irish shamrock plant. The oxalis grows from a small bulb, and as such must be allowed to go dormant, usually about once a year, for two or three months to maintain its vitality.
Place your oxalis plant in a bright, sunny location; it thrives in the bright light but relatively cool temperatures usually found just inside a south-facing window during the winter.
Check the soil dryness in your oxalis pot every few days by pressing a finger about an inch beneath the surface. Water as necessary to keep the soil just barely moist; err on the side of too little water, as if the soil dries out a little between waterings it will not harm the plant.
Fertilize your oxalis every couple of weeks with a half-strength, all-purpose, balanced liquid fertilizer.
Watch for tall, lanky growth on your oxalis, a sign that your plant may need more light or cooler conditions. If you see yellowing on the leaves, you may need to water it less; if it wilts, water it a bit more.
Expect your oxalis to naturally start dropping leaves or "drying up" during the summer or when exposed to temperatures about 75 degrees Fahrenheit. The plant is not actually dying but is going dormant. Stop watering and fertilizing the plant. You can either cut it back yourself or let it die off naturally, then place it, pot and all, in a cool, dark place for a couple of months.
Check on your oxalis every week once two months of dormancy have passed. Once you see signs of new growth, move the plant back to its sunny window and resume your normal watering and fertilizing schedule again.