These masters of camouflage often grow unnoticed on rocks or sand. Their low profile lets them withstand drying winds and go unseen by herbivores. These plants tolerate extreme temperatures of up to 70oC by day, dropping to near freezing at night. Living stones belong to the Aizoaceae family, made up of 140 genera native to the deserts of South Africa. They belong to genus Lithops (from the Greek word lithos, stone) and are recognizable by their two fleshy leaves separated by a slit from which flowers and new leaves emerge. They bloom briefly, abandoning their camouflage just long enough to attract pollinators.
These plants had their heyday back in the times of the dinosaurs, some 150 million years ago. Although they resemble palm trees, they are actually related to conifers, in that they produce cones where the sexual cells form. The plants are either male or female, so it takes one plant of each sex to produce viable seeds. This is a problem for the many cycads on the Red List of endangered species (IUCN). Their popularity with collectors and landscape gardeners, in particular, has caused their populations to decline.
Cycads comprise three plant families and include the genera Cycas, Zamia, Encephalartos and Dioon, all of which can be seen in the Hacienda and Arid Regions Greenhouse.
This kind of cacti, native to moist tropical forests, often grow high up in trees, clinging to them for support without actually feeding on them.
Not much sunlight penetrates through the canopy, so the stems of epiphytic cacti are generally flattened or cylindrical, to capture as much light as possible. Since there are fewer herbivores this high up, their spines are smaller. They produce colourful, fleshy fruit, to attract birds and help spread their seeds.
The best-known epiphytic cactus is probably the Christmas cactus (Schlumbergera x buckleyi), but there are many other interesting species on the market.