Today's photograph and write-up are courtesy of one of my UBC Botanical Garden colleagues, Eric La Fountaine, taken during one of his visits to the Boyce Thompson Arboretum in Arizona. Eric writes:

Because of their interesting and colourful form, species of Melocactus are a favourite of hobbyists. They have two distinct growth phases. In the juvenile phase, the typical-looking spiny globe or cylinder is formed. In the adult phase, a cephalium forms at the growth point of the base. This fuzzy-looking structure is a mass of areoles, which bear the reproductive structures. Cephalia can vary considerably in size, colour and structure. They are slow growing, but may persist for years and produce flowers each season (via Anderson's 2001 work, The Cactus Family).

Melocactus peruvianus is native to Peru and Ecuador at elevations below 1270 metres. Its dark green globose or cylindrical base grows to around 20 cm tall and wide. The cephalia are generally small, but can grow as tall as 20 cm. It forms bright red flowers and fruit.