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Plant of the Month

January 2015

Borzicactus sextonianus

Borzicactus as a genus is just over a 100 years old, having been described in 1909, but it has had a somewhat chequered history. Kimnach (1960) lumped several genera into it, while Hunt et al. (2006), in their survey of the whole cactus family, went even further and combined it with Cleistocactus. Charles (2010), however, reported that 'Recent molecular phylogenetic data assembled by Dr. Boris Schlumpberger (currently being prepared for publication) suggest that Cleistocactus sensu stricto and Borzicactus represent distinct lineages each deserving their own generic rank'. This is followed by Hunt (2013). Borzicactus, therefore, consists of about 20 species with flowers that are diurnal, reddish, tubular and strongly zygomorphic (bilaterally symmetrical) from Peru and Ecuador (Charles, 2010; Hunt, 2013).

Borzicactus sextonianus has also had a tortuous taxonomic history. It began life inappropriately as an Erdisia (Backeberg in Backeberg & Knuth, 1936), then became a Loxanthocereus, Maritimocereus, Borzicactus, Cleistocactus, and currently is back in Borzicactus (Rauh, 1958; Backberg, 1959; Hunt et al., 2006; Hunt, 2013). Kimnach (1960) merged five species of Loxanthocereus and Maritimocereus saying that 'When united, all form a species varying in minor spine characters and..…floral differences are minor'. A broad view of the species was similarly taken by Rowley & Donald (1975), who may have been the first to publish a colour photo of a plant in flower.

Fig. 1. Borzicactus sextonianus in flower, from near Chala, Peru. A fruit with dried flower remains attached is developing near the stem tip.

The plant is variable and two different clones are shown here. The first (Fig. 1) was raised from seed collected by Clarke Blunt and Paul Hoxey. This matches most closely the typical form of B. sextonianus with short, jointed stems, the single stem being only 20cm long with 13 ribs, and spines up to 2.5cm long. The flower is about 10cm long (longer than the 5-6cm generally recorded, eg by Rauh, 1958; Hunt et al., 2006), with a woolly tube. The fruit is up to 2cm long, slightly ovoid, green in colour with the dead remains of the flower being persistent.

Fig. 2. Borzicactus sextonianus (formerly Maritimocereus gracilis) growing in a 32 cm diameter hanging basket.

The second plant, obtained as Maritimocereus gracilis but subsequently renamed as B. sextonianus, is much more robust, with three procumbent or sprawling stems, the longest being 55cm (Fig. 2). It has 10 ribs and the spines are shorter, being up to 1.5cm long. This species is, however, recorded as having stems up to 2m long and 3cm in diameter (Backeberg, 1959). The flower is similar to the other clone at about 10cm long (Fig. 3).

Fig. 3. Borzicactus sextonianus (M. gracilis) flower.

B. sextonianus, then, is a variable species and certainly well worth growing for its magnificently large zygomorphic flowers. It is recorded from coastal Peru, from Mollendo to Chala (Kimnach, 1960).

A puzzle as yet unresolved is who the species name 'sextonianus' commemorates. Backberg (in Backberg & Knuth, 1936) did not record the etymology when he first described the species. Who, then, was Sexton?

Colin C. Walker

References:

Backeberg, C. (1959) Die Cactaceae. Vol. II. Gustav Fischer, Jena.

Backeberg, C. & Knuth, F.M. (1936) Kaktus-ABC. Gyldendal, Copenhagen.

Charles, G. (2010) Notes on Borzicactus in northern Peru. Bradleya 28: 1-14.

Hunt, D. (ed.) (2013) The New Cactus Lexicon. Illustrations. dh books, Milborne Port, England.

Hunt, D., Taylor, N. & Charles, G. (eds.) (2006) The New Cactus Lexicon. 2 vols. dh books, Milborne ऀPort, England.

Kimnach, M. (1960) A revision of Borzicactus. Cact. Succ. J. (U.S.) 32: 8-13, 57-60, 92-96, 109-112.

Rauh,W. (1958) Beitrag zur kenntnis der peruanischen kakteenvegetation. Sitzung. Heidelberg. Akad. ऀWissenschaften. Jahrgang 1958, 1. Abhand. Springer Verlag, Heidelberg.

Rowley, G.D. & Donald, J.D. (1975) Borzicactus sextonianus (Back.) Kimn. Ashingtonia 1: 130-131.

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