Publication: Succulenta (Netherlands) (5) 52 (May 1961)
Description
Lithops karasmontana var. summitatum, is a controversial name, sometimes considered nomina nuda, used to indicate one of the innumerable local form of the very variable Lithops karasmontana.
Taxonomy notes: Gert Cornelius Nel in 1946 wrote that the species L. summitata created by Dinter in 1927, was supposed by the author to differ from L. karasmontana in certain respects. There were two kinds of plants on the same plate both of which he called L. summitata. The one on the extreme left was very decided darker colouration in the depressions than the others. He goes on to say that L. summitata is “hellgrau-blau am Kegelteil” (greyish or brownish blue on the cone part ) with very branched grooves printed superficially and L. karasmontana “taubengrau-blau.” (greysh-blue). This assumes that there is a definite colour called taubengrau‑blau. It is clear that these fine differences in colour cannot possibly be used to distinguish species. Dinter also asserted that the weight of the seed of L. summitata is 0.072 mg. and that of L. karasmontana is 0.064 mg. That is driving the art of distinguishing species to a very fine point indeed. Since these forms coexist in nature, names have a good secondary importance from this point of view and the two “species” result hardly discernible. Moreover there are not “pure” stand or colony of L. summitatum; on the other hand, specimens conforming to the description of this taxon occur in most colonies of L. karasmontana. There seems therefore to be no reason for retaining this as a separate species or variety. Desmond Cole does not mention nor “summitatum” nor “lateritia” in varieties of L. karasmontana. The first is similar to the variety Lithops karasmontana var. lericheana, while the second, it is often presented as a cultivar of Lithops karasmontana var. mickbergensis. But in karasmontana seedlings, there are all possible forms. With patience, time and space, one must be able to produce nice cultivars. Although the distinction between these forms is very artificial to a botanical point of view, it can be justified from a horticultural point of view if the difference is really stable and obvious.
Remarks: In the trade, “summitatum” is often used to indicate Lithops karasmontana var. lateritia and Boer also used the name “var. summitatum” for a cultivar with pure red top of L. karasmontana, but others red topped forms are similar and plants from different localities look more like it.
Bodies (paired leaves): Inversely cone-shaped or club-like truncate, rounded to 25 mm high; a deep, greyish beige cleft dividing tops into unequal or unequal parts, the upper surface light brown with subdued greyish-purple blotching. The “summitatum” still found in the trade (referable to Lithops lateritia) have top of lobe flat or subconvex tinted a pale red-ochre, orange, brick-red or bright rusty-red mostly lined; window semi-opaque, surface slightly uneven, the depressions coloured darker than the ridges, which are coloured a deeper brick-red.
Flowers: White
Specific name: The neuter specific adjectives “summitatum” agrees with Mesembryanthemum but not with the feminine noun Lithops. However the incorrect name “summitatum” (not “summitata”) has been conserved.
Origin and Habitat
Namibia. Karas Mountains.
Cultivation and Propagation
Need an open mineral, fast draining mix and the maximum amount of light you are able to give them. The basic cultivation routine is: Stop watering after flowering. Start watering after the old leaves completely dry. (Usually late March or Early April) Water freely during the growing season, soak the compost fully but allow it to dry out between waterings, no water when cold. Some growers fertilize frequently, some hardly ever. Keep them dry during the winter. Nearly all problems occur as a result of overwatering and poor ventilation especially when weather conditions are dull and cool or very humid. This plant is best for a well lit area (Bright shade to full sun).
Remarks: After flowering in the autumn and extending through winter season the plant doesn’t need watering, but they will still be growing, the new bodies will be increasing in size extracting water from the outer succulent leaves, allowing them to shrivel away. In fact the plant in this time extracts water and nutrient stored in the outer succulent leaves, allowing them to dehydrate relocating the water to the rest of the plant and to the new leaves that form during this period until the old leaves are reduced to nothing more than “thin papery shells”.
Bibliography
Major references and further lectures
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Steven A. Hammer “Lithops: joyaux du veld” Editions Quae, 2010
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Gert Cornelius Nel “Lithops” Hortors Limited, South Africa 1946
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Excelsa, Editions 1-6 Aloe, Cactus and Succulent Society of Rhodesia, 1971
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Alfred Byrd Graf “Exotica, series 4 international: pictorial cyclopedia of exotic plants from tropical and near-tropic regions” Roehrs Co. Publishers, 1985
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Desmond T. Cole & Naureen A. Cole “LITHOPS Flowering Stones” Cactus & Co. Libri. 2005