The Triangle Plant, known botanically as Oxalis triangularis, is a captivating houseplant recognized for its distinct appearance. Its leaves are deep purple, almost black, and form a striking triangular shape, often appearing in sets of three. These unique leaves exhibit nyctinastic movement, folding down at night and unfurling with morning light. Delicate pinkish-white flowers often emerge, adding to its charm. Its distinctive aesthetic and dynamic foliage make it a popular indoor plant.
Caring for Your Triangle Plant
Light
Oxalis triangularis thrives in bright, indirect light. Placing the plant near a window with filtered sunlight is ideal, allowing it to receive gentle morning or late afternoon sun. Too much direct sunlight can scorch its delicate leaves, causing them to burn or develop dry, crispy edges. Conversely, insufficient light can lead to leggy or spindly growth, where stems become elongated and foliage appears sparse. If light is limited, especially in winter, supplementary grow lights can maintain vibrant color and compact growth.
Watering
Water Oxalis triangularis by allowing the top inch of soil to dry out completely before watering. Overwatering can lead to root rot, as it prefers slightly moist but not waterlogged soil. Ensure the pot has adequate drainage holes to prevent water from pooling. During the active growing season (spring and summer), the plant may require more frequent watering; less water is needed during cooler months or dormancy.
Soil
Use a well-draining soil mix for Oxalis triangularis. A mixture of equal parts peat moss, perlite, and sandy soil promotes good drainage while retaining adequate moisture. This plant prefers slightly acidic soil (pH 6.0 to 6.5). A standard premium indoor potting mix rich in organic matter and with good aeration works well.
Temperature and Humidity
Oxalis triangularis prefers moderate room temperatures, ideally between 60°F and 75°F (15°C and 24°C). While it can tolerate slightly cooler temperatures, avoid extremes and sudden fluctuations, such as cold drafts or hot radiators, as these can stress the plant. The plant thrives in average room humidity. In dry indoor environments, increasing humidity through misting or placing a pebble tray with water near the plant can be beneficial.
Fertilizing
During its active growing season in spring and summer, Oxalis triangularis benefits from regular feeding. A balanced, water-soluble fertilizer, diluted to half the recommended strength, can be applied every four to six weeks. Some growers may opt for a higher-phosphorus fertilizer to encourage more prolific flowering. Apply the fertilizer to the soil around the plant’s base, avoiding direct contact with leaves, which can cause burns. Fertilizing should be reduced or stopped entirely during the plant’s dormant period in fall and winter.
Understanding Dormancy and Revival
Recognizing Dormancy
Oxalis triangularis naturally enters a dormant phase, often in winter or when stressed by unfavorable conditions. During dormancy, the plant’s leaves may begin to die back, appearing as if the plant is dying. This is a normal part of its life cycle, allowing the plant to rest and conserve energy.
Managing Dormancy
To manage the plant during this period, gradually reduce watering and cease fertilizing entirely. Move the plant to a cool, dark location, ideally above freezing temperatures. Once the foliage has completely died back, cut off the remaining leaves.
Reviving Your Plant
This dormant period typically lasts a few weeks (three to six weeks). To bring the plant out of dormancy, gradually reintroduce water and light, moving it back to a brighter, warmer spot. New growth should emerge, signaling the end of its resting phase.
Propagating Your Triangle Plant
Method of Propagation
Propagating Oxalis triangularis is achieved through the division of its underground structures: rhizomes or bulbs. These structures resemble tiny pinecones, storing nutrients and producing new shoots.
Timing and Process
The best time for propagation is when the plant is entering or emerging from dormancy, often in fall or spring. To propagate, carefully remove the plant from its pot and gently separate the clumps of rhizomes, ensuring each section has at least one growing point or bud. Plant these divisions a few centimeters apart and 1 to 2 cm deep in small pots filled with a porous, well-draining potting mix. Water lightly after planting and maintain consistent, but not waterlogged, moisture until new growth becomes visible (which may take a few weeks).
Troubleshooting Common Issues
Leaf Discoloration and Wilting
Leaves turning yellow or brown on Oxalis triangularis can stem from several factors beyond normal aging or dormancy. Overwatering, which leads to soggy soil and root rot, is a frequent cause, as is underwatering, resulting in dry, crispy leaf tips. Lack of sufficient light can also cause leaves to turn pale or yellow, while too much direct sun can lead to browning or scorched spots. Sudden wilting can indicate stress from either overwatering or underwatering. Checking soil moisture consistently is the primary step in diagnosing wilting.
Leggy Growth
Leggy or spindly growth, characterized by elongated stems and sparse foliage, indicates the plant is not receiving enough light and is stretching to find it.
Pests
Pest infestations, while Oxalis triangularis is generally resistant, can occur with common houseplant pests like spider mites, aphids, or mealybugs. Signs include fine webbing, sticky residue, or visible insects. Organic treatment methods include rinsing the plant with a strong stream of water, or applying insecticidal soap or neem oil to the affected areas.
Lack of Flowering
Lack of flowering often points to insufficient light, as the plant requires bright, indirect conditions to produce its delicate blooms.