Houseplant · Oxalidaceae
False Shamrock
Oxalis triangularis
Purple, three-cornered leaves that open by day and fold up at night, grown from easy little bulbs.
Bright indirect
55–75°F · 13–24°C
USDA 8–11
6–18 in · 15–46 cm
Overview
False shamrock is grown for its leaves more than its flowers. Each one splits into three deep purple, triangular leaflets that open in the morning and fold down at dusk, so the whole plant seems to breathe through the day. It comes from Brazil and Paraguay, where it grows from small bulbs, and it makes an easy, striking houseplant on a bright windowsill.
What throws most people is the way it dies back. After a hot stretch or in autumn, the leaves yellow and collapse and the pot looks done for. It isn't. The plant is just going dormant, resting its bulbs underground until you give it a cool spell and start watering again, and then it returns in full.
It asks for very little. Bright indirect light, soil kept barely moist, and the patience to let it rest are about all it needs. The one real catch is that every part holds oxalic acid, so it's worth keeping away from pets that like to chew.
Care
The short version: bright indirect light, soil kept barely moist but never soggy, and average room warmth between 55°F and 75°F (13°C to 24°C). Let it die back and rest when it wants to, then water again to wake it.
Light
Give it bright, indirect light for the deepest leaf color. It takes some full sun and copes with partial shade, but too little light leaves the plant leggy and washes the purple out toward green.
Water
Keep the soil barely moist but never wet, letting the top inch or so dry between drinks, since soggy soil rots the bulbs. When the leaves start to die back, ease off and then stop watering altogether to let the plant rest.
Soil
Plant in a loose, well-drained potting mix, soil-based or soilless. It isn't fussy about texture and handles a wide pH band from 6.0 to 8.0, so almost any general houseplant mix works as long as water runs through it freely.
Temperature
Ordinary room warmth suits it, ideally 55°F to 75°F (13°C to 24°C) with cooler nights. It dislikes real heat, which is often what tips it into an early dormancy.
Humidity
Average household air is fine, so there's no number to hit. The plant cares far more about steady moisture at the roots than about the moisture in the air.
Feeding
Feed with a balanced houseplant fertilizer about once a month, but only from spring through fall while the plant is actively growing. Stop completely once it goes dormant, since dormant bulbs can't use it.
Pruning
Pruning is mostly tidying. Pull or snip off any yellowing or dead leaves, and cut out any foliage marked by rust as soon as you see it to stop the fungus spreading.
Repotting
Repot every few years, or sooner once the bulbs crowd the pot and the leaves shrink. Set the bulbs just under the surface in a well-drained mix, which is also the right moment to divide a clump that has grown dense.
Size & spacing
Expect a low mound about 6 to 18 inches (15 to 46 cm) tall, spreading 12 to 24 inches (30 to 61 cm) wide. Its small size and slow, neat habit make it an easy fit for a windowsill or a shelf.
Troubleshooting
False shamrock has few troubles, and the big one looks far worse than it is. Learn to tell a normal die-back from a real problem and the rest is easy. Match what you see below before you reach for the watering can.
Rusty orange pustules and spots on the leaves
This is oxalis rust, a fungus that raises orange to brown bumps on the leaf surface with discolored patches around them. Snip off and bin the affected leaves as soon as you spot them. Give the plant more room for air to move and keep water off the foliage, since the spores spread on wet leaves.
Fix:
- Prune and dispose of diseased foliage
- Improve air circulation and avoid wetting foliage
Leaves yellow and collapse and the plant looks dead
This is almost always natural dormancy, not a sick plant. False shamrock grows from bulbs that rest each year, usually after a hot spell or in autumn, and the leaves simply die back while the bulbs wait underground. Stop watering, clear away the dead growth, and park the pot somewhere cool and dark for about a month before you bring it back into the light and start watering again.
Fix:
- Stop watering and let the leaves dry out
- Remove dead foliage and place the pot in a cool, dark spot for about a month
- Resume watering and return to light when new growth appears
Toxicity
Treat this as a mildly toxic plant, not a harmless one. Every part holds soluble oxalic acid, and the ASPCA lists it as toxic to cats, dogs, and horses. A small nibble usually causes only a sore mouth or a queasy stomach, but a large mouthful can lower blood calcium and strain the kidneys, so keep it out of reach of pets and children.
Toxic to
Cats · Dogs · Horses · Rabbits · Livestock · Birds · People
Cats Caution
A small nibble usually causes nothing worse than drooling and a queasy stomach. It takes a big mouthful of leaves to do real harm, and even then the bitter taste tends to stop a cat well before that point. Watch for vomiting or tremors if one eats a lot.
Dogs Caution
Dogs that chew a leaf or two may drool a little and have an upset stomach for a while. The risk only climbs if a dog works through a real quantity of foliage, which can bring on vomiting and, rarely, lowered blood calcium.
Horses Caution
A passing taste is unlikely to trouble a horse. The concern is grazing on a large or steady amount of the plant, which the soluble oxalates can turn into colic and signs of calcium imbalance over time.
Rabbits Caution
The same oxalates that bother cats and dogs apply here, so keep it off the menu. A stray bite is minor, but rabbits shouldn't be allowed to graze on the leaves.
Livestock Caution
Goats, sheep, and cattle face the same dose-driven risk. Trouble comes from eating the plant in bulk rather than a single mouthful, so keep larger plantings out of reach of grazing animals.
Birds Caution
Best treated as off-limits for pet birds. The oxalic acid in the leaves can irritate the gut, and there's no reason to let a bird pick at it.
People Caution
This isn't a plant grown to eat, and the leaves are tart with oxalic acid. A child who chews on one might get a sore mouth and an upset stomach, so keep it out of small hands, but the bitter flavor usually cuts a taste-test short.
All parts have toxic potential; keep out of reach of pets and children.
Helpline numbers
United States
ASPCA Animal Poison Control: (888) 426-4435 (fee applies)
Poison Control: (800) 222-1222
Canada
Poison Centres: 1-844-764-7669
Varieties
The plant you find sold as false shamrock is nearly always the purple-leaved form. It's the one worth knowing.
Oxalis triangularis subsp. triangularis
This is the purple-leaved form everyone pictures, carrying deep maroon triangular leaflets in threes that fold shut each night or whenever the plant is jostled.
How to propagate
False shamrock multiplies almost on its own, since one pot soon fills with small bulbs that come apart with a gentle pull.
Bulbs & cormsEasy
During dormancy · A few weeks once watering resumes and new growth begins
Wait until the plant is dormant, then tip out the clump and pull apart the many small bulbs, which come away from each other with almost no effort. Tuck them into fresh pots in little groups, just under the surface of the soil. New leaves appear within a few weeks once you start watering again.
DivisionEasy
During dormancy or at repotting · A few weeks
When a pot gets crowded, lift it at repotting time or during dormancy and split the dense knot of bulbs into smaller groups. Replant each group and they settle in within a few weeks.
Myths
False shamrock works like a pothos or philodendron, causing only brief mouth irritation.
The two plants hold different kinds of oxalate. A pothos carries insoluble crystals that only sting the mouth on contact, but false shamrock holds soluble oxalate that the body absorbs, which in large amounts can lower blood calcium and strain the kidneys. The ASPCA lists it as toxic to cats, dogs, and horses, so a big mouthful is a real concern even if a small nibble is not.
When the leaves die back, the plant is dead and should be thrown out.
A bare pot looks finished, but the bulbs are just resting through a normal dormancy. Stop watering, set the pot somewhere cool and dark for about a month, then water again, and fresh leaves push right back up.