The Oxalis triangularis ‘Plum Crazy’, often called the Purple Shamrock or False Shamrock, is a visually striking houseplant prized for its deep, almost black-purple, triangular leaves. This cultivar is popular for the contrast its dark foliage provides against the delicate, funnel-shaped flowers, which range from pale pink to white. Native to Brazil, the plant exhibits a fascinating nyctinasty, where its leaves fold down at night or when stressed, resembling a cluster of purple butterflies. This perennial is commonly grown indoors in containers, where its compact, mounding habit offers a splash of rich color to any bright space.
Setting Up the Ideal Growing Conditions
The vibrant, deep coloration of the ‘Plum Crazy’ foliage depends heavily on receiving sufficient light. The plant thrives in bright, indirect light, such as a position near an east-facing window or set back a few feet from a south- or west-facing window. Insufficient light will cause the leaves to lose their intense purple pigment, resulting in a greener color and leggy growth. Conversely, direct, intense midday sun should be avoided, as it can scorch the delicate leaves, leaving them with crisp, brown edges.
A well-draining soil mix is necessary to prevent corm rot. A well-draining substrate allows excess moisture to escape quickly. A standard, peat-based houseplant potting mix should be amended with materials like perlite, pumice, or coarse sand to increase aeration and drainage. This ensures the underground corms, which store the plant’s energy, do not sit in waterlogged conditions.
Ideal growing temperatures for Oxalis ‘Plum Crazy’ range from 60°F to 75°F (15°C to 24°C). The plant is sensitive to cold drafts and extreme temperature fluctuations, so it should be kept away from exterior doors, heating vents, or air conditioning units. While the plant tolerates average household humidity, moderate humidity levels are preferred and can be maintained with a pebble tray or a humidifier nearby. The container itself must have excellent drainage holes, as standing water in the saucer will quickly lead to saturated soil.
Essential Routine Care: Watering and Fertilizing
Proper watering technique focuses on the “soak and dry” method to protect the plant’s sensitive corms from decay. The soil should be allowed to dry out at least one to two inches deep between waterings during the active growing season of spring and summer. When watering, saturate the soil thoroughly until water runs out of the drainage holes, then discard any water collected in the pot saucer immediately. The plant is less tolerant of water excess than many other houseplants.
Fertilization is only required to support the plant’s growth during its active phase, typically from spring through early fall. A balanced, water-soluble liquid fertilizer, diluted to half or quarter strength, should be applied every two to four weeks. Over-fertilizing can cause the plant to grow too quickly, potentially leading to stretched, weaker stems and a lighter leaf color. Cease all feeding as the days shorten and the plant naturally prepares for its resting period.
Pruning mainly involves removing spent flower stalks and any yellowing or damaged leaves. Removing this dead or dying foliage keeps the plant looking tidy and redirects energy toward new, healthy growth. If the plant begins to look sparse or “leggy,” trimming back longer stems encourages a denser, bushier habit. This maintenance helps ensure the plant maintains its compact form.
Seasonal Management and Troubleshooting
Oxalis triangularis naturally enters a state of dormancy, often triggered by seasonal changes, especially in the fall and winter, or when stressed by excessive heat or drought. During this period, the foliage will begin to wilt, droop, and eventually die back completely, which is a normal and healthy part of the life cycle. When this dieback begins, reduce watering significantly and completely stop all fertilization.
Energy is stored in the underground corms, allowing the plant to survive without leaves for several weeks to months. Once the foliage has died back, remove it, keep the soil nearly dry, and store the dormant pot in a cool, dark location. When new growth begins to emerge, usually in early spring, the plant is signaling its reawakening. At this point, resume regular watering and return the plant to its bright location.
Common houseplant pests like spider mites and fungus gnats can occasionally affect the plant. Fungus gnats are often a symptom of overwatering, corrected by allowing the soil to dry out more completely between waterings. Spider mites can be treated with organic solutions such as horticultural oil or neem oil, applied thoroughly to all leaf surfaces. The plant produces numerous corms, which multiply readily and can be divided during repotting every one to two years to propagate new plants.