Purple Shamrock Care (Oxalis triangularis): Light, Watering, Dormancy and Propagation

Purple shamrock (Oxalis triangularis) is a low, clumping plant with deep purple leaves made of three triangular leaflets that fold down at night like butterfly wings. Small white to pale pink flowers rise just above the foliage. People grow it for the leaf color and because it is easy to divide.

How to identify purple shamrock

Each leaf has three triangular leaflets with a clear crease down the center, held on a long, slender stalk. The Missouri Botanical Garden describes the leaves as dark purple; NC State Extension notes they can range from green to variegated to deep maroon. The leaflets fold at night, when disturbed, and, per the University of Wisconsin, on overcast days. That movement is called nyctinasty, the same thing the prayer plant does.

NC State Extension gives a height of 6 to 18 inches and a spread of 1 to 2 feet. The five-petaled flowers are white to pale pink, in clusters of two to five on leafless stalks, and they close at night too. Bloom runs from spring into summer, and the Missouri Botanical Garden says it often repeats in fall.

Below ground, the plant has storage organs that sources describe in different ways. NC State Extension calls them rhizomes with scale leaves that store water and nutrients, “like an elongated bulb.” The Missouri Botanical Garden says corms or rhizomes; the University of Wisconsin calls them small bulbs. What matters for care is that the plant rides out dormancy on these.

Kew’s Plants of the World Online accepts Oxalis triangularis, with Oxalis regnellii and Oxalis papilionacea among its synonyms. The RHS lists the purple-leaved plant as O. triangularis subsp. papilionacea. The species is native from Peru through Brazil to northern Argentina. Despite the “shamrock” name, it is not related to clover.

Light

Purple shamrock needs more light than most houseplants. NC State Extension and the Missouri Botanical Garden list full sun to part shade, and Oregon State University Extension adds that it prefers bright light. Indoors, the University of Wisconsin recommends a bright, sunny window.

In a hot south- or west-facing window, keep an eye on it in summer: NC State Extension notes that heat can push it into dormancy. For help judging the light in your home, see the houseplant light guide.

Watering

NC State Extension recommends letting the surface of the soil dry between waterings. The University of Wisconsin says to keep the soil barely moist, never wet, and notes most types tolerate slight drying between waterings. The RHS advises watering moderately while the plant is growing.

Watering changes during dormancy. The University of Wisconsin says to stop watering entirely; the RHS says to keep the soil barely moist through winter dormancy. Both aim for the same thing: storage organs that don’t sit in wet soil.

Potting mix and repotting

NC State Extension recommends a loamy potting mix with good drainage. The RHS suggests equal parts loam, leaf mold (or soilless potting mix), and grit, which holds some moisture but drains well.

The best time to repot is at the end of dormancy, before new growth starts. The University of Wisconsin says to set the bulbs just under the soil surface in a well-drained soilless mix.

Humidity and temperature

None of the sources we checked gives specific humidity needs, so normal indoor humidity should be fine.

Temperature matters more. The University of Wisconsin says the oxalis sold as houseplants need cool conditions: no warmer than about 75°F during the day and 15 to 25°F cooler at night. NC State Extension notes that heat or drought can send the plant into dormancy. The RHS recommends a cool room and cool, frost-free conditions in winter.

Dormancy

Roughly once a year the leaves start to yellow and collapse. This is a normal rest period, not a care mistake. The University of Wisconsin puts it in summer, NC State Extension in fall, and the RHS describes a winter rest. Here is the University of Wisconsin approach:

1. When the leaves start to die back, stop watering and let them dry out.
2. Remove the dead leaves.
3. Put the pot in a cool, dark spot. Purple-leaved types only need about a month there.
4. Move it back to a bright window, start watering again, and fertilize or repot.

NC State Extension keeps it simpler: cut back on watering and wait for new growth.

Fertilizing

The University of Wisconsin and the RHS both recommend feeding once a month, only while the plant is actively growing. The RHS specifies a balanced liquid fertilizer. Don’t feed during dormancy.

How to propagate purple shamrock

Division is the easy way. The University of Wisconsin says oxalis are easy to propagate when dormant because the many small bulbs separate easily. NC State Extension also mentions breaking off the scale leaves from the rhizome, which will produce new plants. The RHS and NC State list seed too, but it is rarely used for houseplants.

1. At the end of dormancy, slide the plant out of its pot and gently shake off the soil.
2. Pull the cluster of bulbs apart by hand into several small groups.
3. Plant each group just under the surface of a well-drained mix.
4. Set the pots in a bright spot and start watering lightly.
5. According to the University of Wisconsin, new growth should appear soon after.

For an overview of other techniques, see houseplant propagation methods.

Cultivars and leaf color

The purple color is a trait of the plant, not true variegation. NC State Extension lists several cultivars, two of them with a distinct pattern:

• ‘Fanny’: olive green leaves with a silver pattern in the center and soft pink flowers.
• ‘Atropurpurea’: deep purple leaves with a wide black border and light pink flowers. The University of Wisconsin describes a lighter purple V-shaped blotch on this one.

Other cultivars such as ‘Charmed Wine’, ‘Ebony’, ‘Francis’ and ‘Mijke’ have solid purple to nearly black leaves. None of the sources says what type of pattern ‘Fanny’ or ‘Atropurpurea’ has.

Common problems

Symptom	Cause	Fix
Leaves yellow and collapse	natural dormancy, heat, drought	cut back on water, let it rest, then resume watering
Rusty spots on the leaves	oxalis rust	remove affected leaves
Small insects on the leaves	aphids	rinse off or remove affected parts
Tiny white insects that fly up when touched	whiteflies	remove heavily infested leaves, isolate the plant
Chewed leaves outdoors	slugs	check plants you move outside for summer

The Missouri Botanical Garden and the RHS mention rust, the University of Wisconsin mentions aphids and whiteflies, and the RHS lists slugs for plants grown outdoors.

Toxicity

The ASPCA lists Oxalis (shamrock plant) as toxic to dogs, cats and horses. The toxic principle is soluble calcium oxalates. Clinical signs include drooling and tremors; kidney failure is rare in dogs and cats. If your pet eats some, call your veterinarian. For more plants to keep away from pets, see houseplants toxic to cats and dogs.

For people, NC State Extension rates the poison severity as low. All parts of the plant are potentially toxic, but serious effects are usually limited to eating large amounts. Keep it out of reach of small children.