What is Oxalis triangularis 'Marmer'?

Oxalis triangularis 'Marmer' is a tuberous perennial belonging to the family Oxalidaceae, native to the wetlands of South America — Brazil, Paraguay, Bolivia and Argentina. Its cultivar name 'Marmer' ("marble" in Dutch) refers directly to its most distinctive feature: an intensely marbled foliage of silver and green, of incomparable graphic elegance within the genus.

'Marmer' distinguishes itself from all other forms of Oxalis triangularis through three cumulative, absolutely unique characters: silver marbling far more extensive and contrasted than 'Fanny', a deep purple leaf underside very pronounced as leaves mature, and pearlescent white, barely-pink flowers — larger and far paler than those of the classic green or purple forms.

What are the unique characteristics of Oxalis triangularis 'Marmer'?

• Very extensive, pronounced silver-white marbling: the absolute signature of this cultivar. The triangular leaflets are covered with a large, irregular silver to white marbling that invades a substantial portion of each leaflet against a grey-green background. This marbling is far more extensive and contrasted than in 'Fanny' (where pearlescent marks are discreet crescent shapes) — here, the marble sometimes covers more than half the leaf surface. The graphic effect evokes white marble veins on green stone — a mineral, cool contemporary elegance.
• Deep purple leaf undersides: when a leaf is turned over, or as leaves mature, the lower surface reveals an intense deep purple to violet colour — a striking recto-verso bicolour: silver-marbled green on top, deep purple beneath. This contrast is particularly visible when the leaves fold during nyctinasty or in the wind, adding a unique extra decorative dimension.
• Large pearlescent white to very slightly pink flowers: where 'Fanny' offers clearly pink flowers, 'Marmer' bears flowers of an almost pure pearlescent white, barely tinged with the palest blush. These flowers are also larger than those of other forms. The slightly twisted-edged petals show delicate green venation at their base. They rise on long slender stems above the marbled foliage for a white/green contrast of remarkable purity.
• Fascinating nyctinasty — the plant that sleeps: like all forms of Oxalis triangularis, 'Marmer' folds its leaflets each evening at dusk and reopens them each morning — a slow but clearly perceptible movement. This also occurs during heavy rain or prolonged drought. The folding movement particularly reveals the purple undersides of the closing leaves — a nightly colour transformation.
• Triangular grey-green leaflets, large: as ssp. papilionacea, the leaflets are broad (up to 6–7 cm), triangular, carried on long fine petioles. The base colour is a slightly blue-grey green, different from the vivid glossy green of 'Fanny' — which further enhances the contrast with the silver marbling.
• Edible plant with lemony-acidic flavour: as with all Oxalis triangularis forms, the leaves, flowers and tubers are edible with a pleasant lemony, acidic flavour. The pearlescent white flowers make a particularly elegant edible decoration. Moderate consumption recommended (oxalic acid). Toxic to pets.

'Marmer', 'Fanny', 'Atropurpurea': the guide to the three forms

• 'Marmer' (this form): grey-green foliage with very extensive, pronounced silver marbling, deep purple undersides as leaves age, large pearlescent white near-pure flowers. The most graphic and contrasted of the three.
• 'Fanny': dark glossy green foliage with discreet pearlescent crescent marks, pink flowers. The largest and most verdant form.
• 'Atropurpurea': entirely deep purple foliage marbled with lighter pink, white-pink flowers. The most widely available in commerce.
• All three forms share the same cultivation requirements and the same fascinating nyctinastic behaviour.

How to grow Oxalis triangularis 'Marmer'?

• Light: bright without direct sun. An east- or west-facing windowsill is ideal indoors, or behind a sheer curtain. The silver marbling develops best in good brightness — in deep shade, the marks fade and the foliage greens up. Outdoors, dappled shade or fresh partial shade.
• Soil: draining, humus-rich, fresh, neutral to slightly acidic. Pot formula: 2/3 indoor plant compost + 1/3 perlite or sand. Drainage layer at the pot base. Pot must have drainage holes.
• Planting tubers: plant pseudo-bulbs 5 cm deep, spaced 5 to 8 cm apart, or 5 tubers in a 20 cm diameter pot. In open ground, plant in April after the last frosts.
• Watering: regular but moderate — allow the substrate to dry slightly at the surface between waterings. Fears waterlogged substrate. In prolonged drought, the plant enters temporary dormancy and re-sprouts when watering resumes. Non-calcareous water preferred.
• Temperature: ideally 15 to 25°C. Above 27°C may enter summer dormancy. Hardy to -5 to -6°C in well-drained soil.
• Feeding: flowering plant fertiliser every 2 weeks in spring and summer. Stop completely when foliage begins to yellow.

What are the care requirements?

• Winter dormancy: in November, cut back faded foliage. Move pots to a cool, dark location (5–12°C), stopping all watering. Bring out in February and repot if necessary. In open ground in mild regions, leave in place with a light protective mulch.
• Summer dormancy: if the plant loses leaves in excessive heat or drought, reduce watering and simply wait — it will re-sprout spontaneously.
• Repotting: annually in spring in a slightly larger pot. Right moment for tuber division.
• Deadheading: regularly remove spent flower stems to stimulate new bud production.

Where to grow Oxalis triangularis 'Marmer'?

• As an indoor plant: very bright east- or west-facing windowsill — its silver-marbled foliage and large white flowers create a refined, contemporary decorative effect particularly suited to modern interiors.
• In a hanging basket: the spreading habit and long white flower stems suit hanging culture near a bright window, where the purple undersides of the evening-folding leaves are particularly visible.
• On a terrace or balcony: from May to September in partial or filtered shade. The silver marbling scintillates in natural outdoor light in an incomparable way.
• As a ground-cover in dappled shade: in mild-winter regions, tapestry ground-cover under shrubs or as shaded border edging. Find our other botanical collection curiosities.
• As culinary decoration: the large pearlescent white flowers constitute one of the most elegant edible decorations available among indoor plants.

What are the advantages for collectors?

• The most graphic foliage in the triangularis group: the extensive silver marbling, grey-green base and deep purple undersides as leaves mature create a colour and texture triptych unique — no other cultivated oxalis form offers this combination.
• Nyctinasty reveals the purple underside: each evening as the leaves fold, their deep purple undersides appear — transforming the plant from a daytime silver-marbled appearance to a nocturnal purplish one. A unique, daily botanical spectacle.
• Remarkable white flowers: the large, near-pure pearlescent white flowers contrast magnificently with the marbled foliage — a chromatic pairing of rare purity and elegance.
• Triple ornamental, botanical and culinary interest: as with all Oxalis triangularis forms — decorative, nyctinastic and edible — but with the most spectacular foliage in the group.

How to propagate Oxalis triangularis 'Marmer'?

• By tuber division: in February at spring repotting. Gently separate the pseudo-bulbs keeping 2 to 3 rhizomes per section. Replant immediately in fresh draining substrate.
• No seed propagation: Oxalis triangularis produces no seeds (not self-fertile). Tuber division is the only practical propagation method.