Cactus (Melocactus glaucescens)

KingdomPlantae
PhylumTracheophyta
ClassMagnoliopsida
OrderCaryophyllales
FamilyCactaceae
GenusMelocactus (1)
SizeStem height: 13 - 18 cm (2)
Stem diameter: 12.5 - 24 cm (2)

Melocactus glaucescens is classified as Endangered (EN) on the IUCN Red List (1), and is listed on Appendix I of CITES (3).

This small, rounded or pyramidal cactus is highly attractive. The stem is crowned by a concentration of wool and bristles known as a 'terminal cephalium', which may reach up to 10 cm high (2), and is a feature unique to cacti from the genera Melocactus and Discocactus (4). The bristles themselves are hidden by thick, creamy-white wool through which delightful lilac-magenta flowers emerge (2). The stem of this species is a waxy, light blue colour when young, becoming greyish-green with age. The stem is composed of 7 - 15 ribs with widely spaced areoles from which brown-grey spines emerge (2). Deep magenta, or dark red coloured, rounded fruits develop from the fertilised flowers (2).

Endemic to Bahia in eastern Brazil, this species is only known from four small sites to the north and west of Morro do Chapéu (2).

Melocactus glaucescens inhabits the semi-arid forests and open areas of caatinga and campo rupestre vegetation zones. It is found in sandy soils or pure sand in the open, between low shrubs or amongst small stones (2).

Very little is known about the biology of this cactus.

This cactus is particularly attractive and has been highly prized by collectors over the years; it has suffered greatly from over-exploitation (1). Two of the sites where it occurs are close to a main road and are therefore easily accessible by collectors (3). Hybridisation (cross-breeding) with other Melocactus species also threatens the survival of this cactus in its pure form, and there is evidence of widespread hybridisation at two out of the four known sites for Melocactus glaucescens (2). An additional threat to the species is fire, which is commonly used by farmers in the area to induce re-growth of pasture for livestock grazing (2).

Melocactus glaucescens has been placed on Appendix I of the Convention on International Trade in Endangered Species (CITES) since 1992, effectively banning International Trade in wild plants of this cactus (3). The species has recently been given further protection by the formation of the Parque Estadual do Morro do Chapéu; a new protected area which encompasses most of one of the known populations (2). It is also hoped that additional fieldwork will uncover further populations of this beautiful cactus; one of the known sites was discovered as recently as 2002 (2).

For more information on Brazilian cacti see:
Taylor, N.P. & Zappi, D.C. (in press) Cacti of Eastern Brazil. Royal Botanic Gardens, Kew.

Authenticated (20/3/03) by Dr Nigel Taylor, Royal Botanic Gardens, Kew.
http://www.rbgkew.org.uk

  1. IUCN Red List (August, 2013)
    http://www.redlist.org
  2. Taylor, N.P. & Zappi, D.C. (in press) Cacti of Eastern Brazil. Royal Botanic Gardens, Kew.
  3. CITES (February, 2003)
    http://www.cites.org
  4. Hewitt, T. (1993) The Complete Book of Cacti and Succulents. Dorling Kindersley, London.