2.

Figs 2, 4 –6

Rhoeo spathacea (Sw.) Stearn (Stearn 1957: 198) – Type: same as for Tradescantia spathacea.

Tradescantia discolor L’Hér. (L’Héritier de Brutelle 1789: 5, t. 12) – Type: s. loc. • America calidá, cultivated at the Royal Botanic Gardens, Kew, from a plant potentially originating from Nicaragua; 1787; fl.; s. col. s. n.; lectotype (designated here): K [K 000363274!].

Tradescantia discolor L’Hér. var. discolor (L’Héritier de Brutelle 1789: 5, t. 12) – Type: same as for Tradescantia discolor.

Tradescantia versicolor Salisb. (Salisbury 1796: 216), nom. superfl. – Type: same as for Tradescantia discolor.

Ephemerum discolor (L’Hér.) Moench (Moench 1802: 78) – Type: same as for Tradescantia discolor.

Rhoeo discolor (L’Hér.) Hance (Hance 1852: 660) – Type: same as for Tradescantia discolor.

Tradescantia discolor var. lineata Miq. ex Verschaff. (Verschaffelt 1857: 5) – Type: MEXICO – Quintana Roo • Chetumal, 6.5–7 km N of Tomás Garrido on the road which joins Highway 186 W of Nicolas Bravo; 15 Mar. 1990; fl., fr.; A. C. Sanders et al. 9921; neotype (designated here): US [US 00292627!]; isoneotype: UCR [no. 62683!].

Tradescantia discolor var. variegata Hook. (Hooker 1858: t. 5079) – Type: [Illustration] Original illustration by John Bellenden Kew Gawler at the Illustration section of the Royal Botanic Gardens, Kew’s Library and Archives, later published in Hooker (1858: t. 5079); lectotype (designated here).

Rhoeo spathacea f. variegata (Hook.) Stehlé (Stehlé 1970: 77) – Type: same as for Tradescantia discolor var. variegata.

Tradescantia discolor var. vittata Laurentius ex Regel (Regel 1868: 26) – Type: s. loc., cultivated at the Royal Botanic Gardens, Kew, of unknown wild origin; 23 Jul. 1963; fl.; H. A. Hodson 4; neotype (designated here): K [K 003355761!].

Tradescantia discolor var. vittata Laurentius (Laurentius 1859: 6), nom. nud.

“ Tradescantia agavaefolia hort. ex H. Wildpret ” (K 003355740), nom. not validly publ.

Ephemerum bicolor Moench (Moench 1802: 78), orth. var. (= Ephemerum discolor (L’Hér.) Moench).

Type

MEXICO – Campeche • San Francisco de Campeche, cultivated at the West Indies (most likely Jamaica); 1784–1786; fl.; O. P. Swartz s. n.; lectotype (designated here): S [S-R-6172!]; isolectotype: S [S 07-10830!].

Description

Herbs 10–60 cm tall, 10–70 cm diam., bromelioid rosettes. Stems ascending to erect, base becoming prostrate in older individuals, rooting at base or the nodes touching the substrate; internodes 0.2–3.1 cm long, distally shorter, light green to green to dark green or vinaceous to purple. Leaves spirally-alternate; sheaths (1 –) 1.6–3.4 cm long, green to cream-coloured to pink to purplish-pink becoming vinaceous to purple towards the apex; blades 15.3–35.2 × 2.4–6.8 cm, ascending to patent, adaxially dark bluish-green to greyish-green to dark green to green, abaxially vinaceous to purple, margin vinaceous to purple; midvein slightly conspicuous to conspicuous, adaxially impressed to canaliculate, becoming slightly prominent on the upper third, abaxially slightly prominent, round, secondary veins 3–5 pairs, inconspicuous, becoming more evident on both sides when dry. Synflorescences composed of a solitary main florescence or a main florescence and 1–4 (– many) coflorescences; synflorescence internodes 0.6–3.9 cm long, light green to cream-coloured to purplish-pink; synflorescence leaves (peduncle bracts) present, bracteose or reduced to a bladeless sheath, chartaceous, adaxially cream-coloured to light green, abaxially green suffused with pink to vinaceous. Inflorescences with peduncle 1.1–4.5 cm long, light green to cream-coloured to pale pink; supernumerary bracts present, sometimes absent, when present much narrower than the cincinnus bracts, otherwise similar; cincinnus bracts 1.9–4.8 × 1.9–6.9 cm, subequal to unequal to each other, widely trullate to very widely trullate to rhombic to transversally trullate, conduplicate, overlapping, adaxially light green to green, becoming cream-coloured to light green towards the basal third, pink to vinaceous along the veins and margin, abaxially pink to purplish-pink to vinaceous to purple, becoming cream-coloured to pale pink towards the basal third, vinaceous to purple along the veins and margin, base cuneate to obtuse to truncate, not saccate, apex acute to acuminate; double-cincinni 10–50 - flowered; bracteoles with base suffused with light green, apex suffused with pale pink. Flowers with floral buds 2.8–5.5 × 1.2–3.5 mm, light green to white to pale pink; pedicels 0.8–1.7 cm long, white to light green or pale pink to pale reddish-pink; sepals 3.2–5.9 × 1.7–3.6 mm, oblong to lanceolate to ovate, membranous, not dorsally keeled, hyaline to semi-opaque, light green to white to pale pink, apex acute, straight; petals 4.6–8.1 × 4.3–7.8 mm, widely trullate to very widely trullate to rhombic; stamens with filaments 4.4–8.3 mm long, anthers 0.5–0.8 × 0.7–1.3 mm, connective yellow to ochre to orange-yellow, anther sacs red to maroon to brown; ovary 1.3–2.2 × 1.2–1.7 mm, style 1.9–4.7 mm long. Capsules 2.2–4.2 × 1.7–2.8 mm, oblongoid, when immature pink to reddish-pink to vinaceous, becoming tan-coloured when mature. Seeds 1.8–3.7 × 1–1.7 mm, narrowly oblong to oblong-elliptic, sparsely farinose to farinose, farinae white, outer rim conspicuously scrobiculate, ridges continuous to the ones from the central testa, central testa faintly scrobiculate, ridges radiating from the embryotega.

Palynological description

Pollen flattened-convex in equatorial view. Axis P - 17.4 (18.4 ± 0.5) 19.4 × E - 24.4 (32 ± 1) 45.4 µm. Sulcus 26.7 (35.8 ± 0.7) 45.4 × 12.3 (13.9 ± 0.2) 16.2 µm, membrane verrucate-granulate with sparse nanogranules. Sexine ultrasculpture microverrucate-perforate, sparsely rugulate. Exine 1 (1.1 ± 0.1) 1.25 µm thick; tectum tectate-perforate (Fig. 2 D – F).

Distribution

Tradescantia spathacea is restricted in the wild to the Yucatán Peninsula and surrounding areas, occurring in Belize, Guatemala, and Mexico (Campeche, Chiapas, Oaxaca, Quintana Roo, Tabasco, Veracruz, and Yucatán) (Fig. 4). It is naturalised in Cuba, the Antilles, the West Indies, Honduras, Nicaragua, Costa Rica, and Panama, and widely cultivated elsewhere. It is very frequently found growing around ancient Mayan sites, as it was domesticated for the production of purple dye (Standley and Steyermark 1952).

Habitat and ecology

Tradescantia spathacea can be found growing from 0–600 m a. s. l. in lowland to lower montane rainforests, more commonly as terrestrial or rupicolous, but also as an epiphyte.

Phenology

Tradescantia spathacea flowers and fruits profusely throughout the year if conditions are suitable, especially in cultivation. In the wild, it is most frequently found in bloom and fruit from October to June. Wild forms of T. spathacea flower readily in cultivation, including as indoor container plants, without any apparent requirement for seasonal or environmental triggers. It is strongly to partially self-compatible, with some individuals and populations showing lower pollination success, fruit formation and seed set in selfed flowers. This is supported by cultivation observations by two of us. Plants cultivated by MOOP were found to be highly self-compatible, with over 70 % of flowers developing into fruits and consistently setting viable seeds. Alternatively, plants cultivated by AR had a low fruit set rate when in isolation, with fruits producing (0 –) 1–2 fertile seeds due to abortion.

Vernacular names

Commonly known in Mexico (Spanish) as maguey morado and maguey rojo (Campeche, Quintana Roo, and Yucatán).

Etymology

From the combination of the Greek “σπάθη” (spáthē, meaning “broad blade”) + the suffix “-āceā” (indicating “resemblance” or “similarity”) in reference to the spathe-like cincinnus bracts.

Preliminary IUCN conservation assessment

Tradescantia spathacea has a wide EOO (ca 521,395 km 2) and AOO (ca 1,328 km 2). It is consistently observed in the wild, forming large subpopulations, in addition to being widely cultivated around the world, even becoming slightly invasive in several countries. Thus, following the IUCN (2012) criteria and the IUCN Standards and Petitions Committee (2024) recommendations, we suggest that it be considered Least Concern (LC, criterion B).

Selected examined material

MEXICO – Campeche • Hopelchén, Jardín Botánico de Zoh-Laguna a 10 km al N de Xpujil, camino a Dzibachén; 22 Jul. 1996; fl., fr.; P. Alvaro M. 405; MEXU. – Chiapas • Ocosingo, a 12 km al NO del Crucero de Bonampak; 12 Feb. 2003; fl., fr.; G. Aguilar M. & C. Chancayun 5595; MEXU. – Oaxaca • St. Maria Petapa, jardin de Sra. Crisofora; 14 Sep. 1992; fl.; B. Frei 142; FB, MEXU, ZT. – Quintana Roo • Carretera Chetumal-Escárcega, a 4 km de la desviación de Chetumal; 25 Sep. 2004; fl., fr.; R. Duno de Stefano & B. Torke 2017; CICY, MEXU. – Tabasco • Nacajuca, Tapotzinfo cerca de Masateupa, al norte de Nacajuca; 17 Jan. 1979; fl.; A. Martínez & C. Cowan 1891; MEXU. – Veracruz • Cercanias de San Andres Tuxtla; Jun. 1955; fl.; Dr. Sandoval s. n.; MEXU [MEXU no. 6819]. – Yucatán • Izamal, Walls of Cenotes and ruins; Jun. 1916; fl.; G. F. Gaumer et al. 23381; F, MA, MO, US.

BELIZE – Cayo • Near Terra Nova Forest reserve, ca 21 km N of Black Man Eddy Village and the Belize River; 5 Jul. 1995; fl., fr.; D. E. Atha et al. 974; K, NY. – Orange Walk • Honey Camp; Nov. 1928; fl., fr.; C. L. Lundell 101; K, US. – Toledo • Dolores, ca 40 km SW of Punta Gorda; 1 Feb. 1990; fl., fr.; M. J. Balick et al. 2570; NY, US.

GUATEMALA – El Petén • Uaxactún; 23 Apr. 1931; fl., fr.; H. H. Bartlett 12701; MICH, US.

Notes

Tradescantia spathacea is likely the most well-known species in the genus, easily recognised by its bromelioid habit, strongly discolourous leaves, axillary inflorescences with large boat-shaped bracts, and small, white flowers barely exserted from the bracts. Pollen grains of T. spathacea are smaller [P - 17.4 (18.4 ± 0.5) 19.4 × E - 24.4 (32 ± 1) 45.4 µm] and flattened-convex, with a longer but narrower sulcus [26.7 (35.8 ± 0.7) 45.4 × 12.3 (13.9 ± 0.2) 16.2 µm], membrane verrucate-granulate with sparse nanogranules, sexine microverrucate-perforate and sparsely rugulate, and generally thinner exine [1 (1.1 ± 0.1) 1.25 µm].

Horticulture and cultivars

Tradescantia spathacea is one of the oldest cultivated species in the genus. Natural wild forms of the species are now rare in cultivation, and the majority of cultivated specimens belong to the miniature-sized Bantam Group, established here. Most cultivars are selected for their variegated foliage, which seems to display a range of chimeral albino mutations. We accept six cultivars for T. spathacea, with five of these representing miniature forms, for which we establish a new Group.

Cultivation requirements are flexible, and a range of soil types, light levels, and temperatures is tolerated. Container-grown specimens are susceptible to root and stem rot from excess moisture, but are highly tolerant of drought. Growth is rapid, and propagation is easily achieved through stem cuttings, which also results in the production of numerous plantlets below the cut.