Purple shamrock care guide

The purple shamrock has deep purple leaves made of three triangle-shaped leaflets, like butterfly wings. The leaves fold down at night and open in the morning. Small pink or white flowers bloom above the leaves on and off for months. It grows from small bulbs, and it needs a rest now and then. It is toxic to cats and dogs.

Light

Give it bright indirect light. An east or west window is ideal. A few hours of morning sun deepens the purple.

In low light, the stems stretch long and flop over. Hot afternoon sun scorches the leaves.

Water

Water when the top 2 to 3 cm (1 in) of soil is dry. Water until it drains, then empty the saucer.

The bulbs rot in soggy soil. When it is resting, stop watering. Read how to tell if a houseplant is overwatered or underwatered.

Soil and potting

Use a well-draining houseplant mix.

The bulbs multiply fast and fill the pot. Repot every year or two, in spring or while it is dormant. Plant the bulbs about 2 cm (1 in) deep. See how to repot a houseplant step by step.

Humidity and temperature

Average room air is fine. It likes cool to average rooms between 15 and 24°C (60 and 75°F). Heat above about 27°C (80°F) can push it into rest.

Feeding

Feed monthly with a balanced liquid fertilizer at half strength while it is growing. Skip feeding while it is dormant.

Why the leaves close at night

The leaves fold down like closed umbrellas in the dark and open again in the light. This is normal. They also move through the day to follow the light. If the leaves stay closed in the day, it needs more light.

Dormancy

After months of growth, a purple shamrock may wilt and die back, even with good care. It is not dead. The bulbs are resting.

When the leaves start to die back, stop watering. Cut off the dead leaves. Move the pot to a cool, dim spot and leave it dry for four to eight weeks. When small new shoots appear, move it back to bright light and start watering again. It regrows fast.

Pruning

Pull off yellow or faded leaves at the base. Cut spent flower stems at the soil. If it gets leggy, cut it back to the soil. New leaves grow from the bulbs in a few weeks.

Propagation

Divide it in spring or while it is dormant. Tip the plant out of its pot and break apart the clusters of small bulbs. Plant a few bulbs together in each new pot, about 2 cm (1 in) deep. Water a little and keep them in bright light.

Problems

What you see	Most likely cause
The whole plant wilts and dies back	Dormancy. Let it rest.
Long, floppy stems	Not enough light
Leaves stay closed in the day	Not enough light
Yellow leaves and soggy soil	Too much water
Scorched, faded leaves	Too much hot sun
White powder on leaves	Powdery mildew
Fine webbing under leaves	Spider mites

Pests

Spider mites, aphids, and whiteflies are the most common pests. Rinse the leaves in the shower. Spider mites often push it into early dormancy. Cut it back, let it rest, and it regrows clean.

Pet safety

The ASPCA lists shamrock plant, Oxalis, as toxic to cats and dogs. It contains soluble oxalates. Eating it can cause vomiting and diarrhea. Large amounts can harm the kidneys. Keep it out of reach.

Varieties

• Purple shamrock, Oxalis triangularis, has deep purple leaves and pale pink flowers.
• Oxalis triangularis ‘Charmed Wine’ has dark burgundy leaves and a compact shape.
• Green shamrock, Oxalis triangularis subsp. papilionacea, has green leaves and white flowers.
• Iron cross oxalis, Oxalis tetraphylla ‘Iron Cross’, has four green leaflets with a dark purple center.