When Brian Fearn exhibited a dish containing 40 different living stones at a flower show, one visitor was so fooled that she parked her handbag on top of the plants. Brian, founder of Abbey Brook Cactus Nursery in the Peak District, wasn’t worried; he has been growing Lithops for decades, and knows how tough they are. “You can walk on these plants and not know they’re there,” he explains.
The name Lithops comes from two Ancient Greek words: lithos, meaning stone, and ops, face. They grow in arid climes in southern Africa, fooling hungry grazing animals into thinking they are a cluster of pebbles scattered on the ground rather than a potential meal. They can live almost completely obscured by dust, until they give the game away with a brief annual flush of white or yellow daisy-like flowers. These tough succulents have become popular houseplants, prized for their curious appearance, but growers often find their stones end up a squishy mess – too much water and too little light are usually to blame. The basic shape of Lithops is the same, whatever the species: one pair of succulent leaves fused into a shape that resembles a pair of buttocks. A split down the centre of the leaves conceals the growing point of the plant; from this groove emerges a new pair of leaves every year: they are so economical that all the water and nutrients in the old leaves are absorbed by the new ones, leaving behind a dry husk.
When it comes to colour and pattern, though, every species is different. Among the aforementioned dish of Abbey Brook’s living stones, for instance, there are tiny stones the size of peas in palest dove grey, stippled with lilac; fat cinnamon-coloured leaves spattered with black; and jade green stones etched with veins of lime green. These markings are made up of layers of translucent cells known as leaf windows, that allow Lithops to regulate the amount of light they receive for photosynthesis and prevent overheating. These plants would never be found together in the wild, because each species has evolved to match perfectly the colour of the ground in which they sit – olive-green Lithops olivacea for instance loves to grow in outcrops of quartz, while Lithops ruschiorum is often found growing on feldspar outcrops in its native Namibia, perfectly mimicking the buff and pink hues of the rocks. Brian suggests beginners start with species from the higher-rainfall regions of the Eastern Cape, such as Lithops fulviceps or Lithops aucampiae, as these will tolerate more watering mishaps.
How to care for Lithops
The common feature of all Lithops habitats is a free-draining soil, low in humus, so when choosing a potting mix, Brian uses a 50/50 ratio of horticultural sand or grit and houseplant compost, with a top dressing of grit so there is no risk of water gathering around the plant. In summer, Lithops will revel in as much sunshine and heat as you can throw at them; you can be surprisingly liberal with the watering can – Brian’s Lithops get watered, from above, once a week. When growing as houseplants, the period from the end of September until April is the danger time, when growers must stop watering altogether, move plants to an unheated room with a minimum temperature of 4-7ºC, and let Lithops slip into dormancy. The old leaves will shrivel, but the plants will burst back into life come spring.
How to grow Lithops from seed
Lithops seed resembles dust, so sowing requires nimble fingers, or mix the seed with silver sand for easier handling. The best time to start is autumn or spring, and it’s advisable to use a heated propagator or heat mat so that the seeds are kept at a steady 20ºC as they germinate. Prepare a half-and-half mix of a good quality cactus compost and ready-dampened fine grit or sand, and press the seed on to the surface without covering – they need light to germinate. Place in a plastic bag or under a clear plastic lid, but remove once the seeds have sprouted, in anything from a couple of weeks to three months. Leave in situ until they are ready for pricking out, 12-18 months after sowing.
Jane Perrone is a garden writer