Oxalis triangularis

Classification System: APG IV

Superregnum: Eukaryota
Regnum: Plantae
Cladus: Angiosperms
Cladus: Eudicots
Cladus: Core eudicots
Cladus: Rosids
Cladus: Eurosids I
Ordo: Oxalidales

Familia: Oxalidaceae
Genus: Oxalis
Subgenus: O. subg. Oxalis
Sectio: O. sect. Ionoxalis
Species: Oxalis triangularis
Name

Oxalis triangularis A.St.-Hil., 1825
Synonyms

Homotypic
Acetosella triangularis (A.St.-Hil.) Kuntze, Revis. Gen. Pl. 1: 93. 1891.

Heterotypic
Acetosella catharinensis (N.E.Br.) Kuntze, Revis. Gen. Pl. 1: 93. 1891.
Acetosella oxyptera (Progel) Kuntze, Revis. Gen. Pl. 1: 93. 1891.
Acetosella palustris (A.St.-Hil.) Kuntze, Revis. Gen. Pl. 1: 93. 1891.
Acetosella papilionacea (Hoffmanns. ex Zucc.) Kuntze, Revis. Gen. Pl. 1: 93. 1891.
Acetosella regnellii (Miq.) Kuntze, Revis. Gen. Pl. 1: 93. 1891.
Acetosella yapacaniensis Kuntze, Revis. Gen. Pl. 3[3]: 31. 1898.
Oxalis catharinensis N.E.Br., Gard. Chron. ser. 3, 1: 140. 1887.
Oxalis corumbaensis Hoehne, Relat. Commiss. Linhas Telegr. Estratég. Matto Grosso Amazonas 5, Bot. pt. 6: 30, pl. 125. 1915.
Oxalis delta Vell., Fl. Flumin. 4: 195, t. 178. 1827.
Oxalis glaberrima Norlind, Ark. Bot. 20A(4): 26, pl. 3, fig. 4. 1926.
Oxalis oxyptera Progel, Fl. Bras. 12(2): 489, pl. 103. 1877.
Oxalis palustris A. St.-Hil., Fl. Bras. Merid. (A. St.-Hil.). 1: 128. 1825.
Oxalis palustris var. major A. St.-Hil., Fl. Bras. Merid. (A. St.-Hil.). 1: 127. 1825.
Oxalis papilionacea Hoffmanns. ex Zucc., Akad. Wiss. Wien, Math.-Naturwiss. Kl., Denkschr. 9: 148, pl. 7. 1825.
Oxalis regnellii Miq., Linnaea 22: 545. 1849.
Oxalis regnellii var. catharinensis (N.E.Br.) Norlind, Ark. Bot. 14, no. 6: 10. 1915.
Oxalis tenuis R.Knuth, in?
Oxalis triangularis f. glabrifolia Chodat, Bull. Herb. Boissier, sér. 2, 2: 738. 1902.
Oxalis triangularis subsp. papilionacea (Hoffmanns. ex Zucc.) Lourteig, Flora Ilustrada Catarinense 1(OXAL): 101. 1983.
Oxalis triangularis var. lepida Progel, Vidensk. Meddel. Dansk Naturhist. Foren. Kjøbenhavn 19–20. 1879.
Oxalis venturiana R.Knuth, Repert. Spec. Nov. Regni Veg. 23: 281. 1927.
Oxalis vernalisFredr. ex Norlind, Ark. Bot. 14(6): 9. 1915.
Oxalis yapacaniensis (Kuntze) K.Schum., Bot. Jahresber. (Just) 26, pt. 1: 360. 1900.

References

Saint-Hilaire, A.F.C.P. 1825. Flora Brasiliae Meridionalis 1:102.
Brako, L. & Zarucchi, J.L. 1993. Catalogue of the Flowering Plants and Gymnosperms of Peru. Monogr. Syst. Bot. Missouri Bot. Gard. 45: i–xl, 1–1286.
Lourteig, A. 2000. Oxalis L. subgéneros Monoxalis (Small) Lourt., Oxalis y Trifidus Lourt. Bradea 7(2): 201–629.
Nesom, G.L. 2009.. Taxonomic notes on acaulescent Oxalis (Oxalidaceae) in the United States. Phytologia 91(3).

Vernacular names
English: False Shamrock

Oxalis triangularis, commonly called false shamrock, is a species of perennial plant in the family Oxalidaceae. It is native to several countries in southern South America. This woodsorrel is typically grown as a houseplant but can be grown outside in USDA climate zones 8a–11, preferably in light shade.

The deep maroon leaves are trifoliate, like species in the clover genus Trifolium which are commonly called shamrock, hence the name “false shamrock”. An interesting feature is that the leaves close like an umbrella at night (See the timelapse video below) or when disturbed or if kept under harsh sunlight. The white or pale pink five-petalled flowers also close at night.

Description

Growing to 50 cm (20 in) tall and broad, the subspecies O. triangularis subsp. papilionacea, the purpleleaf false shamrock, is hardy in mild and coastal areas of Britain, down to −5 °C (23 °F), and has won the Royal Horticultural Society’s Award of Garden Merit.[1] It is a perennial plant without aerial stem, formed by leaves borne by a long petiole emerging at the ground level of a tuberous rhizome (5 cm long, over 10 - 15 mm in diameter, fully covered with scales). The leaf is formed of three sessile leaflets, obtriangular to obovate-triangular, glabrous, arranged in the same plane perpendicular to the petiole.[2]

The five densely haired sepals are 5 to 5.5 mm long, narrow and slightly reddish at the top. The five white petals are about 2 inches long and oblong-lanceolate. The stamens and the style are densely hairy. The limb of the wild species is green but purple cultivars have been selected for horticulture. The petiole, soft, whitish, is 15 to 25 cm long. Flowering takes place from spring to autumn.
Movement
File:Oxalis Triangularis Photonasty Timelapse.ogvPlay media
A timelapse of the leaves of O. triangularis closing at night. The recording is at ~750x actual speed and covers a 1.5 hr period of time.

The leaves of O. triangularis move in response to light levels, opening in high ambient light (in the day) and closing at low light levels (at night). During this movement, the leaflets fold at the level of the central vein. This movement is not due to growth and is instead powered by changes in turgor pressure in cells at the base of the leaf. It is an example of photonasty.
Range

The species is distributed in several countries of South America: Brazil, Bolivia, Argentina and Paraguay. It is a neophyte in the United States in the states of Florida and Louisiana. It is also widely found in East India abundantly in states like Nagaland and Manipur.
Cultivation and life cycle
Ornamental shape with red leaves

O. triangularis requires bright indirect sunlight supplemented with a cool indoor temperature of 15 °C (59 °F). It can tolerate higher indoor temperatures but will go into dormancy prematurely and/or begin to take on a "tired" appearance if temperatures exceed 27 °C (81 °F) for prolonged periods of time. It thrives in an average potting soil with good drainage.

Mature plants are cut back to the soil every 3–5 years in early summer or during the dormancy period. Young plants are cut back to the soil every year in early summer or during the dormancy period, until they reach maturity. Fearing frost, they are usually grown indoors. They are planted in soil rich in humus and well drained. They should be watered only when the topsoil looks dry. In winter, they should not be watered.[3]

The subspecies Oxalis triangularis subsp papilionacea has won the Royal Horticultural Society's Award of Garden Merit.[4]
Usage

The leaves are eaten raw or cooked and have an acidic taste due to their oxalic acid content. Leaves and flowers can be used as a decoration for salads. When consuming larger amounts of leaves, the oxalic acid can cause discomfort. The rhizomes are eaten raw or cooked and have a sweet taste.
Propagation

Oxalis triangularis grows from corms, propagated by division. Like other corms, it goes through regular dormancy periods; at the end of each period, the corms can be unearthed, offsets cut and replanted in appropriate soil, where they will grow into new plants.[5]
References

"RHS Plantfinder - Oxalis triangularis subsp. papilionacea". Retrieved 16 April 2018.
Guy L. Nesom: Taxonomic notes on acaculate oxalis (Oxalidaceae) in the United States. In: Phytologia, Volume 91, Issue 3, December 2009.
Flora of Peru (Volume 2) . In: J. Francis Macbride (ed.): Botanical Series . Volume III, No. 2 . Publication (Field Museum of Natural History), Chicago 1949, pp. 83-84
"Oxalis triangularis subsp. papilionacea". RHS. Retrieved 18 January 2021.
"Oxalis regnellii atropurpurea - Purple Shamrock". Plant of the week. Archived from the original on 2011-08-11. Retrieved 2011-06-01.