Velvet cactus mostly displaced by Mexico City

'Feel the surface of this cactus' said Manuel (Bonilla Rodríguez), pointing at a large Opuntia in front of me. Now I've grown Opuntia in the past and I know that they have tiny little irritating 'glochids' among their spines, and you want to avoid getting them stuck in your skin (a magnifying glass and tweezers are needed to remove them all).

It turned out he meant the surface of the cactus stem (or cladode), in between the glochids and spines. It was worth it. So soft and velvety. Quite unexpected in big tough cactus.

It is the aptly named Opuntia tomentosa, its surface covered in soft, short hairs. This is not an uncommon cactus and was one of the first to be brought into cultivation in Europe from its native habitat in Mexico and Guatemala.

Indeed, according to A History of Succulent Plants (by Gordon Douglas Rowley), the Bavarian Prince-Bishop of Eichstatt was in the (late) 16th century able to brag about his giant Opuntia tomentosa: 'an estimated 3,000 joints and 5.5 metres tall with a circumference of 19 metres'. The cactus was one of only a small number of succulent plants from South Africa and Central America to feature in Hortus Eystettensis (by Basil Besler), a book published in 1613 documenting all the plants grown at Eichstatt Castle.

[This illustration is from where is is labelled as Opuntia ficus-indica, and indeed the label hints at that name, but Mr Rowley seems convinced it is Optuntia tomentosa.]

In Australia it is also not uncommon. The Velvet Tree Pear is a declared weed in New South Wales, Northern Territory, Queensland, South Australia and Western Australia. Generally you shouldn't grow or spread it in this country.

If you were to do so (but you can't), or you track some down as an environmental weed, you'd notice the beautiful velvet surface and the colourful flowers - mostly yellow with red outer markings. For the botanical aficionado, as with other cacti, many of the brightly coloured floral adornments are petal-like sepals (the outer, usually green appendages) rather than true petals. We call these petaloids.

In Mexico City the Velvet Tree Pear is part of the original vegetation that lined the large lake now (after draining) replaced by that city. In a restored remnant near the National Autonomous University of Mexico you can find plenty of this species nestling alongside Agave salmiana, Echeveria gibbiflora and the occasional dryland oak, Quercus deserticola.