Light
Lithops want sun, but on their own terms. NC State and Wisconsin Extension both recommend 4 to 5 hours of sunlight in the morning and partial shade in the afternoon. Wisconsin says a southern window is usually best, with an unobstructed eastern exposure as a good alternative; a greenhouse is better still. That is the University of Illinois Extension's direct level, right at the glass.
Too little light is a slow killer. Wisconsin describes the sequence: the plant grows slender and elongated, leans to one side, loses its coloring and turns greenish, and eventually dies if conditions do not improve. NC State calls this etiolation. The opposite risk is real too. Wisconsin warns that moving a plant abruptly into brighter light can sunburn it fatally, so make every increase over a week or two, and watch hot afternoon sun through a south window in summer.
| Range | Bright light to direct sun, best in direct sun |
|---|---|
| Foot-candles | 300 to 1,500 fc (3,229 to 16,146 lux) |
| Windows | South, East · morning sun only |
| Sources | North Carolina Extension Gardener Plant Toolbox; University of Wisconsin-Madison Extension; University of Illinois Extension |
Water
Water by the plant's stage, not by the date. Wisconsin Extension gives the general cycle, which NC State's profile follows. Water from late spring into early summer. Stop when the plant goes dormant in summer; if it shrivels badly, give just enough to restore a firm look, wetting only the top half inch of soil. Resume in late summer or early fall when growth and flowering begin, a stage you can recognize when the fissure starts to open. NC State's rule for that period is once every 2 weeks.
Then comes the step that matters most. Wisconsin says lithops should be left totally dry through winter and spring, so the old leaf pair dries out while the new pair develops. By early spring the new body should be visible, emerging from the fissure at about 90 degrees to the old one. Water again only when the remains of the old leaves are completely shriveled and dry. Water given too soon makes the old leaves try to keep growing, and the plant does not develop properly; NC State adds that overwatering causes yellow, mushy leaves, brown spots and splitting.
When you do water, drench the pot and let it dry out completely, which Wisconsin estimates at probably 1 to 2 weeks, then wait a couple more days. Water in the morning so the top layer dries fast. Wisconsin's summary is the best rule for this plant: if in doubt, don't.
| Rule | When the mix is dry all the way down: only in the growing periods, drench the pot and let it dry out completely, then wait a little longer |
|---|---|
| Winter | No water at all through winter and early spring while the old leaf pair is absorbed and the new one forms; resume only when the old leaves are completely shriveled and dry. |
| Watch for | Watering follows the plant's yearly cycle, not the calendar: late spring into early summer, then late summer and fall. |
| Stop watering during summer dormancy; if a plant shrivels badly, moisten only the top half inch of soil. | |
| Water given while the old leaves are still plump makes them keep growing, and the new pair cannot develop properly. | |
| Sources | North Carolina Extension Gardener Plant Toolbox; University of Wisconsin-Madison Extension |
Soil and pH
Use a cactus mix or a fast-draining, gritty blend: Wisconsin suggests adding sharp sand, perlite or decomposed granite to houseplant potting mix. The pot is more important than it looks. Lithops have an extensive root system, so Wisconsin recommends pots about 3 to 5 inches deep with drainage holes, larger than the plant's size suggests. Set the top of the plant slightly above the soil surface rather than buried as in the wild, and topdress with gravel, which looks natural and keeps the body dry.
| Mix | Cactus mix, or houseplant potting mix with plenty of sharp sand, perlite or decomposed granite, in a pot 3 to 5 inches deep with drainage holes. |
|---|---|
| Ingredients | cactus potting mix, sharp sand or decomposed granite, perlite, gravel topdressing |
| Sources | North Carolina Extension Gardener Plant Toolbox; University of Wisconsin-Madison Extension |
Humidity
Lithops thrive in low humidity, according to Wisconsin, and some species in the wild depend on mist or fog for moisture. Indoors, dry air is no problem. What they do need is fresh air: stagnant, humid conditions around a wet pot invite rot, and Wisconsin notes they handle very high temperatures as long as ventilation is good.
Temperature
NC State says lithops thrive between 65 and 80°F (18 and 27°C) and can tolerate 90 to 100°F, but not temperatures below 40°F (4°C); they must be protected from freezing. On a winter windowsill, keep them back from cold glass on frosty nights. Summer heat is less of a worry than summer water, since the plants are dormant then and a wet pot in hot weather rots quickly.
| Minimum | 40°F (4°C) |
|---|---|
| Ideal | 65 to 80°F (18 to 27°C) |
| Humidity | Dry air is fine. Thrives in low humidity and needs plenty of fresh air, especially in hot weather (Wisconsin Extension). |
| Sources | North Carolina Extension Gardener Plant Toolbox; University of Wisconsin-Madison Extension |
Fertilizer
Feed rarely. Wisconsin Extension advises fertilizing lithops sparingly with a low-nitrogen, high-potassium product. The University of Illinois Extension's general ceiling for houseplants is once every 1 to 3 months, and for living stones the slow end of that range, at reduced strength and only during a watering period, is plenty. Never feed during the dry winter and spring phase, when the plant is living on its old leaves.
| When | Sparingly, and only while the plant is being watered in active growth, every 8 to 13 weeks, none in winter |
|---|---|
| What | Low-nitrogen, high-potassium fertilizer, such as a cactus or tomato feed, half strength |
| Sources | University of Wisconsin-Madison Extension; University of Illinois Extension |
Work out the dose for your watering can with the fertilizer dilution calculator →
Repotting
Lithops rarely need repotting. Wisconsin says it is quite possible to keep one in the same pot for 10 or 20 years, and the plants can live 40 to 50 years. Unlike most succulents, they do not want a snug pot: the extensive roots need depth, so if yours came in a shallow nursery cell, move it into a 3 to 5 inch deep pot. Handle the taproot gently, replant in dry mix with the body just above the surface, and water only when the plant is in a growing phase.
- Roots circle the bottom of a pot shallower than 3 inches
- A clump of heads has filled the surface
- The mix has broken down and stays wet after watering