Oxalis triangularis, commonly known as the Purple Shamrock or False Shamrock, is a popular houseplant celebrated for its distinctive, deep purple, triangular-shaped leaves. These leaves possess a characteristic called nyctinasty, where they fold up at night or when the light is low, resembling a cluster of butterflies. The plant is typically grown from small, lumpy underground storage organs that are technically rhizomes or corms, though they are often casually referred to as bulbs. Planting these rhizomes is the standard method to begin cultivating this charming Brazilian native in your home.
Essential Preparation Before Planting
The optimal timing for planting Oxalis triangularis rhizomes indoors is usually in late winter or early spring, aligning with the plant’s natural emergence from dormancy. Selecting the right container is the first step, and it must have drainage holes to allow excess water to escape freely. Proper drainage is important because the rhizomes are susceptible to rot if they sit in soggy soil.
The ideal growing medium is a lightweight, well-draining potting mix that still retains moisture. Standard houseplant potting soil can be improved by amending it with materials like perlite, sand, or peat moss. This mixture ensures the soil remains loose and aerated, preventing compaction around the developing roots. A good ratio involves mixing a commercial potting mix with one part perlite to four parts soil to achieve the necessary balance of moisture retention and drainage.
Step-by-Step Planting Instructions
The small, segmented storage organs are technically corms or rhizomes, not true bulbs. To ensure a full, lush display, plant multiple rhizomes together in the same pot. When filling the container, leave enough space at the top so the final soil level is slightly below the rim.
The proper orientation of the rhizome is with the pointed or narrower end facing upward. This is the growing point from which the new foliage will emerge, and sometimes small growth tips may already be visible. Place the rhizomes about one to two inches apart within the pot to allow for clustered growth. They should be planted approximately one to one and a half inches deep, then covered gently with the remaining potting mix. Lightly firm the soil surface around the newly placed rhizomes to settle them.
Immediate Post-Planting Care
After the rhizomes are settled, provide the correct light environment to encourage sprouting. Oxalis triangularis thrives in bright, indirect light, such as that provided by an east-facing window or a few feet away from a south or west-facing one. Intense, direct afternoon sun should be avoided as it can scorch the delicate, dark purple foliage.
The initial watering strategy aims to wake the rhizomes without causing them to rot. Lightly dampen the soil after planting to settle it, but avoid soaking the medium until new growth is visible. Until the first shoots appear, the soil should be maintained only slightly moist, as overwatering during this stage causes the dormant corms to decay. The plant prefers average indoor temperatures ranging between 60°F and 75°F (15°C to 24°C). With consistent warmth and proper light, new shoots typically emerge within three to six weeks.
Understanding the Growth and Dormancy Cycle
Oxalis triangularis is a perennial plant that naturally goes through a period of rest, known as dormancy. This natural cycle ensures the plant’s long-term health and is typically triggered by changes in environmental conditions, such as reduced light, cooler temperatures, or excessive heat and dryness. For houseplants, dormancy often occurs during the winter months, but it can also happen during the summer.
Signs that the plant is entering this resting period include the foliage becoming limp, wilting, or completely dying back. When this happens, stop watering and fertilizing entirely. The pot, containing the dormant rhizomes, should be moved to a cool, dark, and dry location, such as a basement or closet, where it can rest undisturbed for several weeks or months.
To bring the plant out of dormancy, return the pot to its location with bright, indirect light and begin watering lightly again. The reintroduction of moisture and warmth signals to the rhizomes that it is time to resume the growth cycle. New shoots will quickly emerge, and the plant can then be cared for under its normal growing regimen.