Plant of the month: August
Can you see the tall, spiky plant to the right between the benches? It is looking right at you! Its name is Pachycereus pringlei and it is arguably the tallest living cactus in the world. Cacti (or, botanically speaking, plants in the family Cactaceae) are stem succulents that have evolved in the Americas. They all share one trait that is unique to this family – the areole. An areole is a modified shoot and as a meristematic region it can grow into a branch or a leaf or a flower. Four years ago, the plant looking at you was nine feet tall (more of that later); in its natural habitat of north-west Mexico, it can grow to over nineteen metres. Night-flowering and pollinated by bats, a fully grown specimen can consume hundreds of litres of water during a rainstorm.
The first plants that graced our planet needed wet habitats. During the course of evolution plants have adapted to changing conditions. As such, cacti can be seen as among some of the most highly evolved of plants. To cope with arid conditions, they have modified their leaves into spines; their stems into photosynthetic organs; and their skin into a waxy cuticle. They absorb carbon dioxide at night (Crassulacean Acid Metabolism), can absorb water rapidly by utilising salts in their roots and can expand and contract in response to rainfall and drought through the mechanics of ribbed stems.
Four years ago, this Pachycereus pringlei was almost touching the roof of the Arid House at Winterbourne House and Garden. It was cut down and re-rooted, and earlier this year donated to us. In late May it was planted out on the Loudon Terrace, where it can be seen, looking at you.