House plants who impersonate rocks

... The lure of lithops begins with a double-take, the realization that these pebbles are actually plants, alive and growing. See these succulents in a specialty nursery — or run across them at Home Depot or Lowe’s — and you may feel like a gem collector who can’t resist a few more cabochons. Perhaps the mottled pink ones? Or maybe the lovely dove gray flecked with green?

Lithops can be almost as tough as stones too. They’ve adapted to the most inhospitable growing conditions imaginable: sandy deserts that get no rain most of the year. Ascetics of the plant world, lithops spurn rich soil and regular water. Conventional wisdom about how to keep a plant happy doesn’t apply. . . .

“The secret is to observe them, which, by the way, is not a chore but a pleasure,” Hammer says.

He suggests growing lithops in coarse, fast-draining soil. In their native habitat, the plants thrive in mineral-based soils poor in organic matter, and they receive only a few inches of rain a year. A good soil mix is more white than brown: Think one part commercial potting soil with twigs removed, and two parts perlite or pumice. If you use perlite, which floats, add a top dressing of gravel. The addition of decomposed granite will help toughen the plants.

Grow lithops in pots, not garden beds. Indoors, Hammer says, “they grow very well in a bright eastern window, close to the glass.” A southern exposure will work as well; west isn’t quite as good; and northern will invite failure.

The type of pot doesn’t matter much, but if you’re concerned about overwatering, clay will keep them drier — and will last longer than plastic.

The plants need four or five hours of full sun daily. Given too little light, lithops will elongate. Morning sun is ideal. Protect them from scorching afternoon sun in summer. If new plants have been in a greenhouse, introduce them to sun gradually so they don’t burn. One trick is to drape them with a paper napkin for several days.
Eccentric little rock stars

Known as the living stone plant they are from South Africa and love heat and drought. Flowers come in the fall and early winter. They are succulents, so lots of heat, light and very little water is called for.

Put them on your sunniest windowsill. Plant them in sand or gravely soil. Shallow pots are best. The average rainfall in their native climate is 2″ a year. Go very easy on the watering.

Flowers come up through the split in the middle and look like tiny daisies.

After flowering bodies form new leaves and the old leaves dry up. What leaves you ask? The part of the plant you see is the leaves. They generally get one new pair of leaves per year.

Only water in the summer if they appear to begin to wrinkle or shrivel. Give them a good once a year drenching when you see flowers. Water very lightly when you water the rest of the year. Do not water when new leaves are forming. New leaves draw water from older leaves that is why the older ones shrivel. Water again when old leaves are gone and new leaves are growing.

If they begin to get thin and leggy they need more light. Often they will lean towards the light when it is too little for them. If they receive too much sun they will get white burn spots.

Keep them warm, over 40’F.

More information:
A huge selection of pictures of various Lithops
Cultivation of Lithops