Each plant is unique. Size, shape, fullness, and variegation will vary.
Lithops are small succulents native to the dry regions of southern Africa, where much of the plant grows at or below the soil surface and the exposed leaf tops resemble the surrounding stones. Each body is formed by a pair of thick, water-storing leaves separated by a central fissure. Their colors and markings vary tremendously between species, from gray, tan and brown to green, rust and pinkish tones. Mature plants can produce daisy-like flowers from the center of the leaf pair, usually during their active growing period. Their unusual appearance is only part of what makes Lithops different from most houseplants. Their entire watering cycle follows the way they replace and recycle their leaves.
Lithops remain extremely compact above the soil, but below the surface they develop a substantial root system with a taproot that extends much deeper than the visible plant suggests. Each year, a new pair of leaves develops inside the existing pair. The new leaves gradually use the water stored in the old leaves, causing the old pair to wrinkle, collapse and eventually become thin and papery. Do not peel or remove those shrinking leaves. They are supplying the developing plant with stored water and nutrients. An established plant may eventually divide and produce two bodies where there was previously one.
For natural light indoors, place Lithops directly in a south-facing window or within approximately 1 foot of a west-facing window. They prefer approximately 2,000–4,000 foot-candles at the leaves. Foot-candles simply tell you how much light is actually reaching your plant. Lithops naturally grow in extremely bright environments, and insufficient indoor light can cause the normally compact body to stretch upward and become taller and narrower. If a plant has been growing in substantially lower light, increase its exposure gradually rather than moving it immediately into dramatically stronger light.
Under a grow light, use a full-spectrum 5000–6500K fixture positioned approximately 6–10 inches above the plants, aiming for the same 2,000–4,000 foot-candles at the leaves. Kelvin describes the color of the light, while foot-candles tell you how much light is actually reaching the plant. Healthy Lithops should remain low and compact rather than stretching upward toward the fixture. Raise or lower the light as needed to maintain useful intensity as the growing setup changes.
Soil is especially important with Lithops. Use a very gritty mix made primarily from mineral material with only a small amount of organic potting material. Approximately 80–90% mineral material and 10–20% organic material is a useful target. The mineral portion can include ingredients such as pumice, perlite, lava rock, coarse horticultural grit or other porous, fast-draining mineral material. The finished mix should look and feel much more like grit and small stone than conventional potting soil. Avoid a rich, peat-heavy mix that stays wet around the roots. Use a container with a drainage hole, and choose a pot deep enough to accommodate the taproot rather than placing the plant in an extremely shallow decorative container.
Water when your plant needs watered, but with Lithops, the plant’s stage of growth determines whether it needs water at all. During active growth, usually around late summer into fall, the plant can be watered thoroughly and then allowed to dry completely. Dry soil by itself is not a reason to water again. Look at the established leaf pair. When an actively growing plant begins showing slight wrinkling or loss of firmness after the mix has been dry, it may be using its stored water and be ready for another watering. Lithops should not be kept lightly or continuously moist.
When a new pair of leaves begins developing inside the old pair, stop normal watering. This commonly happens through winter into early spring. The old leaves are supposed to wrinkle dramatically, collapse and look as though they are dying. During this stage, that appearance is not a request for water. The developing leaves are absorbing the moisture stored in the old pair. Adding water while the plant is trying to complete this process can leave it with more moisture than it can use. Wait until the old leaves have been largely absorbed and are thin and papery before gradually returning to active-growth watering. The plant’s physical stage matters more than the date on the calendar.
Once the old leaf pair has been absorbed, the new pair becomes the active plant and watering can gradually resume when it shows that it is using its stored moisture. During very hot summer conditions, Lithops may also slow their growth and use very little water, so another dry period can be normal. This is why a weekly or even monthly watering schedule does not work well for them. At different points in the year, the exact same plant may need a thorough watering or may need no water at all.
Learn to distinguish normal leaf replacement from a thirsty plant. Wrinkling of the old outer leaves while a new pair is visible inside is normal and is a reason to withhold water. Slight wrinkling or softening of the established active leaf pair, after the previous leaves have already been absorbed and the root zone has been dry, can indicate that the plant is using its stored water. A body that becomes unusually swollen, translucent or splits in unexpected places can be a reason to evaluate whether it has received more water than it can currently use. Stretching upward and losing the compact stone-like shape points toward insufficient light rather than a watering problem.
Success looks like a Lithops that remains compact, develops a new leaf pair normally and completely absorbs its previous leaves before continuing its next growth cycle. Flowering can occur once a plant is mature enough, but the clearest sign of success is simply watching it complete that annual cycle without trying to force growth with additional water. With Lithops, understanding what stage the plant is in before reaching for the watering can is far more important than following a schedule.
