You’re a botanist, what’s this then? (Or Tradescantia spathacea, this one’s for you mum!)

Tradescantia spathacea, from my parents garden.
©Phoebe Richardson-Moy

That sentence may sound familiar to many of you who frequent this blog (followed closely by “Botany, so you’re a gardener then?” but we won’t go in to that). Being asked about the identity of a random plant that mysteriously turned up in someone’s garden is something you get used to. This blog is what happens when the universe conspires and the planets align and a class project coincides with an innocent question from the mother of a botanist…

My parents live on Lanzarote, in the Canary Islands, and I’m studying MSc Plant Diversity in Reading, so when my mother asked me about this plant my first answer was “Have you tried Google?”. After talking to a friend on Facebook who was able to give us the common name ‘Moses-in-the-Cradle’, we were able to find that this beautiful and distinctive plant is called:

Tradescantia spathacea

Common Names: Moses-in-the-Cradle, Boat lily, Oyster plant. (1)

Tradescantia spathacea is a ground dwelling plant but it is known to grow on rocky outcrops, walls and to even be epiphytic on trees and other niches with no soil.

This species is a sub-succulent herb whose leaves are imbricate, overlapping each other to form a rosette.

Tradescantia spathacea, showing leaves forming rosette, and flower-containing bracts. ©Phoebe Richardson-Moy

The leaves are green on the adaxial side and vividly purple underneath, on the abaxial side.

Leaves showing the green upper surface and purple lower surface in Tradescantia spathacea. ©Phoebe Richardson-Moy

The leaves are approximately 7.5cm wide and can reach up to around 30cm in length, this also being the average height of the plant. The leaves arise from a trunklike stem, which can be up to 20cm tall, however I have not personally seen a specimen that has a visible stem, but ones where it seems that the leaves grow from the base. (2)

The flowers are what gives this species its common names, as the small, white and three petalled flowers grow inside ‘boat-shaped’ purple bracts in the leaf axils.

Tradescantia spathacea’s boat-like bracts containing the small white flowers.
©Phoebe Richardson-Moy

The flowers and seeds are produced all throughout the year, the flowers are hermaphroditic and for cross-pollination is pollinated by insects, but can also reproduce via self-pollination in the absence of pollinators. It can reproduce by seed, cuttings, offshoots and plant fragments.(3)

A young T. spathacea grown from seed. ©Phoebe Richardson-Moy

This species is also slightly toxic for both humans and animals and can cause itching and reddening of the skin. If ingested it causes irritation to the mouth and causes abdominal pains, even being poisonous in large enough quantities. I had no problems when touching the plant, however reactions are more likely on bruised leaves or when in contact with the sap, so beware! (1)(3)

Geography

The species is native to southern Mexico, and central America, specifically Belize and Guatemala. However it has been introduced as an ornamental and a houseplant to many tropical regions, including China, Japan, Africa, southeast Asia, USA, the West Indies, Australia, the Pacific islands and the Canary Islands where I first saw it. (2)(4)

The genus Tradescantia (to which this species belongs) are native to the ‘New World’, from southern Canada to Northern Argentina and the West Indies. Some species have become naturalised in Europe, Africa, Asia, Australia and on various oceanic islands. Tradescantia spathacea is a perfect example of this. (2)

Map of Commelinaceae family distribution. From the APG website, unable to find © status. (5)

The family to which this genus belongs are mainly pantropical, reaching into temperate zones, however none of this family is native to Europe. (5)

Tradescantia spathacea was probably introduced as an ornamental plant to different countries in the nineteenth century. It is considered an invasive species in various places, the Florida List of Invasive species classifies it as ‘Category II’ (increased in abundance but not yet altered natural plant communities) but on the Pacific islands it is threatening ecosystems and regular monitoring is recommended wherever it is present. (3)

Tradescantia as a genus

Commonly known as the Spiderworts, Tradescantia is a genus consisting of 75 species of perennial plants. The species belonging to this genus tend to be upright or scrambling plants, common to wooded areas and fields and which grow to approximately 30 to 60cm high. (2)

The leaves of this genus tend to be long and thin, and the flowers are most commonly blue, but can also be pink, purple or white (as is the case of Tradescantia spathacea).

There are various members of this genus that can cause toxic reactions, characterised by red, itchy skin, as previously mentioned Tradescantia spathacea is an example of this.

A curious fact about some members of this genus is that the cells of the stamen hairs are coloured blue, but when exposed to ionising radiation (i.e. Gamma rays), these cells mutate and change to be coloured pink, making them one of the few known tissues that can effectively show ambient radiation levels. (6)

Part of a bigger family

Tradescantia belongs to the family Commelinaceae following the APG III system (and was the same in APG and APG II). Many species from this family are cultivated as ornamentals. The members of this family tend to be herbs with soft and fleshy leaves with closed sheaths. (5)

Another view of T. spathacea bracts where the flowers are contained. ©Phoebe Richardson-Moy

The inflorescences usually are many-flowered and often have large, leafy, boat-shaped bracts (as we have seen in Tradescantia spathacea). The flowers always lack nectar, and usually last for one day only and tend to be blue or pink. However, the variation in morphology, especially in the flower and inflorescences, is considered to be exceptionally high amongst the angiosperms. (7)

Uses

The main use of Tradescantia spathacea is as ornamentals and houseplants in tropical and temperate regions where this plant has been extensively commercialised for many years, as mentioned earlier this plant was introduced to other countries in the 1800’s. (3) There are many plants of this growing in the Americas bed in our Tropical Glasshouse.

It is also used in traditional medicine in Mexico and southeast Asia, where the flowers and leaves are used to treat cancer, superficial mycoses, coughs, colds, and dysentery. Scientific papers on the medicinal value of Tradescantia spathacea have been published, and it has been reported to possess anti-microbial, insecticidal, anti-inflammatory, anti-cancer and anti-fertility activities. (8)

And finally

So, there you have it, the most complete answer to this “You’re a botanist” question that I can come up with! To think that the pretty little plant in my mother’s garden comes with such a history, colonising countries, getting classified as invasive, that it can be toxic it you fancied eating enough of it, but at the same time has anti-cancer properties…

After this, I am going to try to not get frustrated when someone asks for the name of a garden plant from a place I’m not familiar with. I’ll remember that every garden plant has an origin, and a story. And that this is the reason I am a botanist.

You are welcome Mum, and thank you for the challenge.

References

(1) Floridata: Tradescantia spathacea [Online] Available here. Retrieved 21-11-2014.

(2) David R. Hunt,  (1986). “Campelia, Rhoeo and Zebrina united with Tradescantia: American Commelinaceae: XIII“. Kew Bulletin 41 (2): 401–405.

(3) Invasive Species Compendium. Tradescantia spathacea datasheet. [Online] Available here. Retrieved 21-11-2014.

(4) Kew Royal Botanic Gardens. World Checklist of Selected Plant Families [Online] Available here. Retrieved 21-11-2014.

(5)Angiosperm Phylogeny Website. Commelinaceae family. [Online] Available here. Retrieved 21-11-2014.

(6) Sadao Chikawa,  (1972). “Somatic Mutation Rate in Tradescantia Stamen Hairs at Low Radiation Levels: Finding of Low Doubling Doses of Mutations“. The Japanese Journal of Genetics 47 (6): 411–421.

(7) Jean H. Burns, Robert B. Faden, and Scott J. Steppan (2011). Phylogenetic Studies in the Commelinaceae Subfamily Commelinoideae Inferred from Nuclear Ribosomal and Chloroplast DNA Sequences. Systematic Botany, 36(2):268-276.

(8)Sriwanthana, Busarawan, et al. “In vitro effects of Thai medicinal plants on human lymphocyte activity.” In vitro 29 (2007): 1.