These are highly developed members of the Mesembryanthemum family which also includes the ‘Livingstone Daisy’ which many people grow in their gardens. The body comprises a pair of fused leaves with a variable sized fissure in the centre, through which the flower appears, usually sometime between July and December. Flower colour is normally yellow or white, depending on the species.
The whole genus comes from South Africa and Namibia. Because these are very high light level areas, the plants deal with this by growing relatively flush with the ground, the bodies consisting of large, relatively transparent water cells with the plant chlorophyll contained on the inner surface of the leaves. The tops of the leaves contain a windowed area (not always apparent) through which the light shines. This is reduced in level via the window and water cells, and the normal plant processes take place inside the plant body rather than on the outer surface, as with normal plant leaves. Each year the plant regenerates its leaves, the water content of which is transferred from the old to one or more new bodies, leaving the dried remains of the former to protect the latter until it is time to grow again. This normally takes place between October and May in the UK.
Cultivation is fairly simple, a free draining growing medium (I use a John Innes no 2 compost with 50% small grit mixed with it). Because the bodies renew each year, it is not necessary to feed, provided re–potting takes place every 4 to 5 years. Give them as much light as possible, but ensure that there is adequate movement of air over the plants to prevent scorch. It is best not to grow the plants flush with the soil in cultivation, just bury the roots in the soil and top dress with small stones. Water once the old leaves have dried up (usually in early June) and continue until the end of October, then stop until the same time the following year.. The plant shown is Lithops marmorata which has a fairly wide distribution, occurring from western Bushmanland into Namaqualand. The windows in this species are fairly apparent and the flower colour, as can be seen, is white.
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