Origin and Habitat: Endemic to Brasil (only known from four small sites from Chapada Diamantina, to the north and west of the municipality of Morro do Chapéu, Bahia, extent of occurrence ca 1,500 km2.
Altitude: 700–900 metres above sea level.
Habitat: Its natural habitats are semi-arid forests and open areas of caatinga and campo rupestre where it grows between low shrubs or on flat exposed sloping areas, on sandy soils or pure sand or on crystalline rock outcrops with accumulation of gravel.
Ecology: The showy colours, tubular structure, and abbundant nectar of flowers suggests that this plant is ornithophilous (Pollinated by birds. Chlorostilbon aureoventris and other hummingbird are the most frequent flower visitor but some butterfly species visit the flowers too. Melocactus glaucescensSN|11349]]SN|23685]] is often found growing, at least in some portions of its areal, along with Melocactus paucispinusSN|23701]]SN|23701]] and Melocactus concinnusSN|23685]]SN|11349]]. The overlap in the flowering period and the similarity in the guild of pollinators favour the occurrence of natural hybridization. The dispersal of seeds is carried out mainly by lizards and also by some ants. Fruit emergence and extrusion rates are concentrated in the morning, increasing their chances of being taken on the same day, thus avoiding desiccation and predation. The species is threatened by small-holder and agro-industrial agriculture, cattle ranching and local collection. Man-made fires and illegal plant collection also pose a threat.

• Melocactus glaucescens Buining & Bredero

Description: This is a small species with highly attractive bluish stems and tall creamy-white cephalia.
Stem: Solitary, rounded or pyramidal 14-18 cm tall, 14-25 cm in diameter, waxy, light blue colour when young, becoming greyish-green with age.
Ribs: 7-15 (but most frequently 11) acute.
Areoles: Widely spaced 1-1,8 cm apart.
Radial spines: 4-6(-7) brown-grey, the lowermost up to 2,5 cm long..
Central spines: 1(-2) stouter, ascending, of the same colour up to 1,5 cm long.
Terminal cephalium: up to 10 cm high, crowned by a concentration of short bristles almost hidden by thick, creamy-white wool.
Flowers: 2,1 mm long, 6 mm wide, delightful lilac-magenta .
Fruit: Rounded to egg shaped, up to 12 mm long x 6 mm wide, deep magenta, or dark red, developing from the fertilised flowers.
Seeds: 1-1,3 mm long, 0,8-0,9 mm wide, strongly tuberculate at end opposite hilum.
Remarks: Isolated plants of Melocactus glaucescensSN|23685]]SN|23685]] rarely produce fruits (presents self-incompatibility and allogamy).

Bibliography: Major references and further lectures
1) COLACO, Miguel A.S. et al. "Reproductive biology of Melocactus glaucescens Buining & Brederoo and M. paucispinus G. Heimen & R. Paul (Cactaceae), in the Chapada Diamantina, northeastern Brazil." Rev. bras. Bot. 2006, vol.29, n.2, pp. 239-249. [Online] <http://www.scielo.br>. Downloaded on 14 February 2014
2) Stuart Max Walters “The European garden flora. 3.[Angiospermae], Dicotyledons. [Casuarinaceae to Aristolochiaceae]” Cambridge University Press, 1989
3) Edward Anderson “The Cactus family” Timber Press, Incorporated, 2001
4) David R Hunt; Nigel P Taylor; Graham Charles; International Cactaceae Systematics Group. "The New Cactus Lexicon" dh books, 2006
5) Urs Eggli, Leonard E. Newton "Etymological Dictionary of Succulent Plant Names" Birkhäuser 2004
6) Taylor, N. P. 1991. "The genus Melocactus (Cactaceae) in Central and South America." Bradleya 9: 1–80.
7) Nigel Taylor, Nigel P. Taylor, Daniela C. Zappi, “Cacti of Eastern Brazil” Royal Botanic Gardens, Kew, 15/gen/2004
8) Braun, P., Machado, M., Taylor, N.P. & Zappi, D. 2013. Melocactus glaucescens. In: IUCN 2013. "IUCN Red List of Threatened Species." Version 2013.2. <www.iucnredlist.org>. Downloaded on 14 February 2014.

Cultivation and Propagation: These cacti are not the easiest things to grow and aren’t plants for beginners. In northern hemisphereMelocactus glaucescens grows from April to October, it can’t endure long stretches of total dryness, and also too much water will rot it, as its weak root systems tends to be inefficient at sucking up water from wet soil. Nonetheless, again as a result of their tropical origins, they need a fair amount of water, but allow the soil to dry quite a bit before watering again. Melocactus rests from October to April but can’t stand cold, or even fairly cool temperatures, so is indispensable to keep it above 8-12°C at all times, severe damage or death occurring at temperatures that the great majority of cacti wouldn’t mind in the least and prefer more frequent water in winter than other cacti, say once a month. Do not feed in winter.
The root system is weak and generally resents being repotted and can take a long time to re-establish. The soil mix should be very quick draining, prefers very bright light, not as much as the most arid growing cacti, but plenty nonetheless.
Propagation: Exclusively by Seeds. Sow in February-march in a light, sandy, porous soil. Cover germinating tray with glass to prevent seed from drying out. Germination is most successful at a temperature of 18 to 22° C.