Appearance

Crassulaceae

Crassula

The family that gave Crassulacean Acid Metabolism its name — leaves that keep their stomata shut through the day and take in carbon dioxide at night instead, which is why they lose so little water and why they grow slowly. Kew accepts 220 species and gives the genus range as cosmopolitan, though the centre of it is southern Africa.

Native to Cosmopolitan, with most species in southern Africa

How Crassula generally wants to be treated

Species pages start from this and record only where they differ.

Light
Four or more hours of direct sun a day, or a bright south-facing window — two extension services give the same figure independently. No source at this level publishes a lux number. Too little light gives deep green leaves, drooping stems and no red in the margins; the compact shape is a light effect, not a genetic one.
Water
Let the mix dry out, then water deeply. Overwatering drops the leaves and rots the stem, and it is the way most of these die. Cut back sharply in winter — that is well documented as practice, though it is horticultural practice rather than anything derived from the plant's physiology, and it is worth being honest about which.
Humidity
No requirement. Ordinary dry room air is what it is built for.
Temperature
65-75 °F (18-24 °C) by day and 50-55 °F (10-13 °C) at night is the published optimum. The cool nights are not an indulgence — nocturnal gas exchange is when a CAM plant does its work.
Substrate
Free-draining and gritty — a cactus mix, or ordinary compost cut heavily with sharp sand or perlite. Depth matters less than drainage; these are shallow-rooted.
Fertilizer
Very little. Clemson feeds once every three or four months. A CAM plant's daily carbon gain is modest by design, so feeding it like a fast-growing foliage plant gives it nothing it can use.
Propagation
Leaf and stem cuttings, both easy. Let the cut surface callus before it touches the mix. No extension source I found gives a rooting timescale, which is worth knowing before you conclude yours is slow.
Dormancy
None documented as a physiological rest. Growth slows in winter with the light and the temperature, and the watering follows.
Common problems
  • Root and stem rot from overwatering — far and away the commonest cause of death, and the reason the pot matters more than the plant
  • Leggy stems with widely spaced deep-green leaves and no red margins mean too little light
  • Mealybugs and spider mites. But do not reach for insecticidal soap: Clemson warns it may damage jade plants and Wisconsin flags phytotoxicity independently. Alcohol on a cotton bud is the documented alternative
  • Leaf drop after a period of drought is normal and recoverable; leaf drop on a wet plant is not
  • A plant that never flowers is usually beside a lamp. Flowering is triggered by long nights, so a plant getting evening light indoors will not do it
  • Every part is toxic to cats and dogs, and unusually the toxic principle has never been identified

Sources 1234567891011

In the collection