Oxalis regnellii 'Triangularis' (Purple and Black False Shamrock) - Oxalis regnellii triangularis like cool air and moist soil while they are growing. A suitable compost for shamrocks consists of 2 parts peat moss to 1 part loam to 1 part sand. Bright indirect light is best, but they will grow in lower light levels. Fertilize weekly while they are growing with a balanced fertilizer. No matter what you do, they will seem at times to be unhealthy and lose their leaves. When this happens, they are "tired," so let them "rest." Shamrocks are bulbs, and they require a dormant period every once in a while. Restrict all watering. As with any bulb, let the leaves die back naturally. Do not remove any leaves until they are brown. Let the bulbs stay dormant for 3 to 4 weeks, then water and fertilize. In most indoor-grown shamrocks, this dormant period occurs 2 to 3 times a year.