Living stones are unusual succulents that have evolved to resemble the pebbles and rocks that litter their native habitats through southern Africa. These very small plants hug the ground and grow extremely slowly—it can take years for a plant to fill its pots with new leaves. Structurally, living stones are comprised of two fused leaves above ground that connect to an underground stem with a long root.
The leaves are extremely thick, and the degree of fusion depends on the species. Some species appear to be a single leaf, with hardly any evidence of the leaf fusion, while others are deeply lobed to the level of the soil. These plants are great collectibles, but require a careful hand with the water. Too much water and the leaves will burst, or the plant will die from beneath. If you provide them with good conditions, they will flower in mid- to late summer with white and yellow daisy-like flowers that emerge from between the leaves.
Light: Living stones thrive in full sunlight, so provide as much light as possible. Weak lighting will cause elongated leaves and washed out patterns on the leaves.
Water: Living stones have a definite annual cycle (see Grower's Tips below) that should be carefully followed. In the summer, as the plants are dormant, it is okay to lightly water them if the leaves shrivel.
In general, plants should not be watered during their summer dormancy or the winter.
Temperature: Warm in summer (household temperatures are fine) and colder in winter months (down to 55˚F at night).
Soil: Use a cactus mix or very fast-draining potting soil mixed with sand.
Fertilizer: Fertilizer is not necessary.
Most living stone species can be propagated from. Seedlings typically take two to three years to reach maturity and begin flowering.
Living stones are very slow growing, small plants, which makes them ideal as houseplants (once you get the hang of their watering schedule). Older plants form attractive clumps of "pebbles" in their pots, which are highly prized. In general, plants should only be repotted if there are cultural problems (soggy soil) or the plant has outgrown its dish container, which will only happen every several years.
The group of plants known as living stones all is from the Mesembryanthemum family of plants. Within this family, there are several genera that are found in cultivation, including the Lithops and Conophytum. Within these two genera, there are dozens of species, and their identification can be confusing for anyone except hardcore enthusiasts and biologists. Indeed, because the growing requirements for most living stones are similar, it's best to pick your plants based on your preference. That said, however, different species have different cycles and may flower and go into dormancy at different times of the year. Watch your plants closely to gain clues.
Living stones develop a new set of leaves every year, with new leaves emerging in the fall and growing through the winter and into the summer. In late summer, the plant will go dormant, and water should be severely restricted to prevent bursting leaves. The flowers appear near the end of summer or fall, first showing up as a small bud forcing its way between the leaves and growth will begin again. It's safe to water during this period. The leaves will still be growing heading into the winter, but you should stop watering, even as the older leaves shrivel up and encase the new growth. In the spring, it's safe to begin lightly watering again as the plant begins to grow again, heading toward their summer dormancy period and the emergence of new leaves in the fall. Keep an eye out for common pests like scale, which can chew away at the plant's foliage and cause serious damage.
They can be dealt with using a good pesticide, but make sure it's eco-friendly!