Purple Shamrock
Oxalis triangularis · False Shamrock
A low, clumping plant from southern South America with deep maroon-purple leaves, each made of three triangular leaflets. Every evening those leaflets fold straight down and the flowers shut, then they reopen by morning.
Family
Oxalidaceae
Origin
South America
In the wild
Grows from corms
Indoors
0.15–0.45 m
Growth
Moderate
With pets
Toxic
Where it's from
Brazil and Paraguay
South American native
From Brazil and Paraguay, naturalised in Florida, Louisiana and parts of India.
Grows from corms
A geophyte that stores energy in underground corms and retreats into them through bad seasons.
Outdoors: zones 8–11
Hardy to about minus 5°C. Elsewhere a houseplant, or lifted and stored over winter.
The plant that sleeps
Each evening the three triangular leaflets fold straight down like a closing umbrella, and the flowers shut with them; by morning they open again. This daily turgor-driven movement is called nyctinasty. The same retreat instinct sends the whole plant dormant for weeks, only to spring back from its corms.
A daily clock
Leaves open by day and fold down at night, driven by water pressure in the leaf, not by growth.
Not dead, just napping
Heat or the end of the season triggers dormancy. Cut back water and new shoots return in four to six weeks.
It multiplies underground
One pot quietly becomes a colony of corms, so dividing them gives free plants every year or two.
How to keep it
LightBright light
A bright window keeps the purple deep and triggers blooming. North-facing is too dim.
WaterLet the surface dry
Let the top dry between waterings; it cannot sit in wet soil. Stop watering once it goes dormant.
HumidityAverage is fineOrdinary household humidity suits it. No misting needed.
TemperatureCool, around 15°CPrefers cool to moderate rooms. Above about 27°C it can wilt and go dormant; freezing kills the corms.
SoilLoamy, well-drainedA free-draining mix in a pot with a drainage hole. Plant corms about an inch deep.
FeedingLight, when growingA light feed during active growth. Pause when it is dormant.
DifficultyEasyBeginner-friendly and low-maintenance, as long as it drains well.
With petsToxicSoluble calcium oxalates. Drooling and tremors if eaten in quantity; dose-dependent.
PropagationDivision of cormsLift the clump and separate the small corms, then replant about an inch deep.
RepottingEvery couple of yearsWhen the clump crowds the pot. Divide the corms at the same time.
What the data says
What it costs
A cheap, mass-produced seasonal plant, sold hard around St Patrick's Day. No collector market.
$5–20
Corm packs run cheapest; small potted plants a little more. Named selections like 'Mijke' cost only slightly extra.
IUCN · Not evaluated
In the wild
The comfortable case: abundant in cultivation, with no conservation tension anywhere.
Not evaluated on the IUCN Red List, and there is no recorded threat. It is mass-propagated from corms and has even naturalised beyond its native range, in Florida, Louisiana and parts of India. Thriving everywhere it grows.
When it sulks
Mushy stems, collapseOverwatering or no drainage. The most common problem by far.
Leaves stop openingUsually dormancy from heat or the end of the season, not death. Cut back water and wait.
Faded, pale purpleToo little light. Move it somewhere brighter.
Orange pustules on leavesOxalis rust. Prune off the diseased foliage.
Wilting in heatMove it to a cooler, shadier spot.
Varieties & company
The varieties
subsp. papilionaceaMijkeAtropurpureaGreen wild type
Pairs with · keep apart from
CalatheaFernsPeace LilySnake PlantCactiSucculents
A new plant, every week.
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