Lithops (N. E. Br.)

Lithops purchased at Kew Gardens

Lithops recently purchased at Kew Gardens

Family: Aizoacea, Subfamily: Ruschioideae, Vernacular names: Living Stones, Stoneface, Pebble Plants, Flowering Stones, Mimicry Plants.

Lithops, native to the deserts of South Africa, are often called ‘living stones’ for obvious reasons, evolving as they have to blend in to the dry, rocky habitats of southern Africa. The genus Lithops represents 37 species and is part of the Aizoaceae family otherwise known as ‘Mesembs’ which constitutes around 1,900 species of succulent plants.

Bisected Lithops leaves

Bisected Lithops leaves

For Lithops, protection against herbivorous predation in such arid environments is paramount.  The plants have grow two succulent leaves each season which will open into a slit, the following seasons two leaves grow up and out of this. These leaves even have ‘weathered’ looking ridges and lines on them which improves camouflage. The stem is greatly reduced in these plants meaning the leaves are essentially fused to the taproot. They grow new leaf pairs every year, going through a cycle of active growth and dormancy (growth in cooler months, rest and dormancy in hot summer months).  When you see a plant with many sets of leaves, therefore, you know that it is at least several years old. Interestingly, in the wild they grow with only the top of their leaves poking out of the ground which makes them less easy to spot, able to retain moisture and keeps them cool. In cultivation, however, they tend to do better raised mostly out of the soil.

Lithops in the great outdoors

Lithops in the great outdoors

Usually Lithops must be 3-5 years old before flowering. When they do so it is in autumn and early winter and tends to result in a yellow or white daisy-like flower head.

Lithops pseudotruncatellus

 

The enthusiasm for Lithops has led to their over exploitation in the wild, forcing some species to near extinction. The cultivated varieties are still readily available in garden centres and are grown world-wide.

 

References:

- USDA, ARS, National Genetic Resources Program.
Germplasm Resources Information Network – (GRIN) [Online Database: Accessed 18th Feb 2013].

- http://www.lithops.info/en/ [Online: accessed 18th Feb 2013]

- http://faculty.ucc.edu/biology-ombrello/POW/living_stones.htm [Online: Accessed 18th Feb 2013]

Images:

- http://www.plantsystematics.org/cgi-bin/dol/dol_terminal.pl?taxon_name=Lithops&rank=genus

- http://www.lithops.info/en/botany/dissection.html

- http://www.kkagrawal.com/lithops1.htm

- http://letterslinedup.blogspot.co.uk/2010_04_01_archive.html

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