Whether you grow shamrock plants indoors as a houseplant or outdoors in frost-free zones, oxalis triangularis is simple to grow and care for if you use correct proportions of water and sunlight. Oxalis triangularis is a deciduous ground cover with small flowers and clover-like leaves. Its triangular-shaped leaves fold along the vein and look like butterflies fluttering above slender stems. All Oxalis leaves are light sensitive, opening to receive sunlight and closing at night or when under shade – sometimes looking like many perched butterflies.
Oxalis triangularis comes in two varieties: green leaves with white flowers, often referred to as Oxalis Regnellii, and purple leaves with white or pink flowers, commonly called Purple Shamrock. Their bright foliage can bring color to otherwise drab winter windowsills when grown in pots indoors.
To grow shamrocks, place up to five bulbs in an 8” pot to create a houseplant, or tamp the bulbs into the soil outdoors, spaced 3” apart and 1 to 2” inches deep. Water the soil well, but make sure it drains adequately, as too much moisture can cause the roots to rot. You can expect to see flowers within 10 weeks.
Too little light can cause your plant to get thin and weak. Place the plant in a southern window (northern if you are in the southern hemisphere) or possibly a western or eastern. Better yet, let your plant spend time outdoors during good weather for a boost – just be sure to acclimate the plant first.The purple shamrock is sensitive to light, and its leaves close up at night and in overcast conditions. Plant or place it an environment free from temperature extremes. The brighter the light source, the more colorful the foliage and flowers. Avoid prolonged periods of direct sun and heat, however, which can cause the shamrock to go dormant prematurely.
In general, aim for a daytime temperature of 60-70F, especially when the plant is blooming. When planted outdoors, purple shamrocks should fare well in frost-free regions that correspond with the U.S. Department of Agriculture’s “hardiness” zones 6 through 10.
When watering your shamrock, keep the soil barely moist, and allow the top inch of soil to dry before the next watering. Use a houseplant fertilizer mixture every two to four weeks to maintain the plant’s overall health.
Like other plants grown from bulbs, the purple shamrock requires one or more “rest periods,” particularly during autumn. If your plant looks “tired” after it blossoms, stop watering it and let it go dormant for approximately one month, then fertilize and water as usual once it rejuvenates.
You will not typically see many pests on Oxalis. Check beneath the leaves for aphids, spider mites and other pests before bringing it into your home and you should be fine. If you ever do end up with an infestation you can’t get a handle on, simply wait until the plant goes dormant again. Remove all the leaf litter and the bugs are gone.
Height: 6-12 in (15-30 cm)
Light: Bright light
Water: Allow top inch of soil to dry between waterings.
Humidity: Average indoor humidity
Temperature: Prefers cool temperatures, especially while in bloom; 55-65°F, 13-18°C at night/not warmer than 75°F, 24°C during the day.
Soil: Any good potting mix.
Fertilizer: Feed every 2 weeks while plant is growing with a balanced liquid fertilizer diluted by half. When blooming stops, feed every other month.
Propagation: Divide the plant by gently pulling apart its small, tuberous roots into smaller clumps and potting them in separate containers.