lithops- Living Stones

Lithops is a genus of succulent plants in the ice plant family, Aizoaceae. Members of the genus are native to southern Africa. The name is derived from the Ancient Greek words (líthos), meaning “stone,” and (óps), meaning “face,” referring to the stone-like appearance of the plants. They avoid being eaten by blending in with surrounding rocks and are often known as pebble plants or living stones. The formation of the name from the Ancient Greek “-ops” means that even a single plant is called a Lithops.

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History

The first scientific description of Lithops was made by botanist and artist William John Burchell, explorer of South Africa, although he called it Mesembryanthemum turbiniforme. In 1811, Burchell discovered a specimen when picking up a “curiously shaped pebble” from the ground. Unfortunately, the documented physical description was not detailed enough to be sure which Lithops he had discovered and the name Lithops turbiniformis is no longer used, although for many years it was applied to what is now known as Lithops hookeri.

Because their camouflage is so effective, new species continue to be discovered, sometimes in remote regions of Namibia and South Africa, and sometimes in well-populated areas where they simply had been overlooked for generations.

Taxonomy

Common Name: Lithops, living stones, living stone plant, split rocks, split rock plant, pebble plant, Karas Mountains living stone, Lesliei living stone, Lithops terricolor, Truncate living stone, Salt-dwelling living stone

Scientific Name: Lithops aucampiae, Lithops dorotheae, Lithops fulviceps, Lithops hookeri, Lithops karasmontana, Lithops lesliei, Lithops localis, Lithops optica, Lithops pseudotruncatella, Lithops ruschiorum, Lithops salicola, Lithops verruculosa, Lithops viridis and other species

Family: Aizoaceae

Light: Full sun to partial shade

Water: Extremely light to none at all

Temperature: 65-80 degrees optimal, can take heat to 90-100, do not go below 50 degrees

Humidity: Tolerant of short bursts of humidit

Soil: Gritty or rocky, extremely well draining sandy soils preferred

Fertilizer: None to extremely light high-phosphorous

Pests: Spider mites most common. Can also attract thrips, scale insects, mealybugs, aphids, snails, slugs, and root knot nematodes. Mice and other small animals may eat it for its water content.

Diseases: Almost none, but can develop rot if overwatered, exposed to cold conditions, or damaged

Individual Lithops plants consist of one or more pairs of bulbous, almost fused leaves opposite to each other and hardly any stem. The slit between the leaves contains the meristem and produces flowers and new leaves. The leaves of Lithops are mostly buried below the surface of the soil, with a partially or completely translucent top surface known as a leaf window which allows light to enter the interior of the leaves for photosynthesis.

During winter a new leaf pair, or occasionally more than one, grows inside the existing fused leaf pair. In spring the old leaf pair parts to reveal the new leaves and the old leaves will then dry up. Lithops leaves may shrink and disappear below ground level during drought.

Lithops in habitat almost never have more than one leaf pair per head, presumably as an adaptation to the arid environment. Yellow or white flowers emerge from the fissure between the leaves after the new leaf pair has fully matured, one per leaf pair. This is usually in autumn but can be before the summer solstice in L. pseudotruncatella and after the winter solstice in L. optica. The flowers are often sweetly scented.

The most startling adaptation of Lithops is the coloring of the leaves. The leaves are fenestrated (having perforations, apertures, or transparent areas), and the epidermal windows are patterned in various shades of cream, grey, and brown, with darker windowed areas, dots, and red lines, according to species and local conditions. The markings function as remarkable camouflage for the plant in its typical stone-like environment.

Lithops are obligate out crossers and require pollination from a separate plant. Like most mesembs (ice plants), Lithops fruit is a dry capsule that opens when it becomes wet; some seeds may be ejected by falling raindrops, and the capsule re-closes when it dries out. Capsules may also sometimes detach and be distributed intact or may disintegrate after several years.

Propagation

Lithops seedlings

Propagation of Lithops is by seed or cuttings. Cuttings can only be used to produce new plants after a plant has naturally divided to form multiple heads, so most propagation is by seed. Lithops can readily be pollinated by hand if two separate clones of a species flower at the same time, and seed will be ripe about 9 months later. Seed is easy to germinate, but the seedlings are small and vulnerable for the first year or two and will not flower until at least two or three years old. A tray of assorted varieties looks like candies.