Synonyms:

Lithops rubra
Mesembryanthemum opticum var. rubrum

Habitat:

Lithops optica var. rubra is native to Namibia, in particular from the west area of Lüderitz. It grows among the rocks, scattered in small colonies, in semi-arid climates, at variable ranges of altitude, on rather sandy soils. Its native climate its cool due to the proximity of the Atlantic ocean, that provides frequent fogs and a rainfall concentrated in the winter, between 20 and 50 millimeters a year.

Description:

Lithops optica var. rubra is actually identical to the regular species Lithops optica, with the exception of the red-purplish colour of the stem, that earned the cultivar the name “Rubra”, meaning “red”. It is a dwarf succulent plant that grow at ground level and form clusters of purplish stems similar to pebbles, adapted for camouflaging among the rocks of their rocky, arid environment and for minimizing the water loss through the stem surface. With age, the clusters of L. optica var. rubra can include up to 20 little bodies. Like any Lithops, L. optica var. rubra has a main pair of opposite, ear-like leaves with a central fissure, from which new vegetative bodies and flowers sprout. The pair of leaves is often unequal, slightly oblong, always smooth and with perfectly rounded margins. The margins often show spotted patterns, coloured in paler red, more pinkish. The body becomes wrinkled during dry summers and it’s replaced by the new one sprouting from the central fissure. In the Autumn, the flowers sprout from the central fissure. They are daisy-like and have crowded, numerous white petals opening late in the day and closing at sunset. Flowers are soon replaced by the fruits, which are 5-chambered capsules that open when moistened (it is probably a mechanism to ensure that seed dispersal occurs only at sufficient humidity to allow germination).

Cultivation:

Lithops optica var. rubra is rather easy to grow: here below are our cultivation tips.

Keep in a bright spot all year round except in Summer, when it should be kept in light shade, in a cool spot.
Lithops optica var. rubra can survive at temperatures down to -5ºC, as long as it’s kept dry. Nevertheless, to stay safe, we suggest to keep indoors or to shelter it during the Winter months.
Water scarcely, always waiting for the soil to dry up before each irrigation. Water once every one-two weeks, depending on the temperature, from mid-spring to autumn. With the fall of the temperatures, reduce the watering dfrequency until stopping completely in Winter and early Spring, to allow the plant to have the right vegetative rest.
Choose a well-draining substrate. A standard soil for cactaceae will do good. Also a sandy gravel mixture will be ok. The best results will be obtained with a shallow pot, not much wider than the plant’s diameter.
This tiny plant, like all Lithops, is very slow-growing, so you won’t need to repot so often. However, once every three years, you might repot and change the substrate. The right period to do so is late Winter-early Spring, at the end of the vegetative rest.
Fertilization is not indispensable. You may feed this plant once a year by diluting a specific fertilizer for succulents in watering, but the plant will thrive anyway. Also, an excessive amount of fertiliser in the “diet” of Lithops may cause a weakening of its leaves tissues, making it subsceptible to rot. 

Propagation:

The propagation of Lithops optica var. rubra can be carried out through seeds, cuttings or division of the “bodies”. Plants can be hand pollinated, using a small paint brush. Always cross different clones as the plants are self-sterile. Seeds will remain viable for many years, if stored in cool, dry places. Sow them in Spring/Autumn: germination will occur in one-two weeks, at 15-21ºC. To obtain a complete germination of all your seeds, remember to keep the substrate moist all the time until you see the plantlet sprouting. Shoots might be taken off though Lithops prefer to grow in undisturbed clusters: which is the main reason why growers prefer sowing as a reproduction method.

Curiosity:

Lithops optica is dominant, and the form rubra is recessive. This means that seeds of the form rubra will more probably produce a regular Lithops optica instead of a new Rubra. Being their natural pollinators absent outside of their natural habitat, plants can be hand pollinated, using a small paint brush. Cross different clones as the plants are self-sterile. The seed will remain fertile for many years if stored in a cool dry place.

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