Origin and Habitat: Type Locality 15 km East of Mariental, Namibia.
Habitat: It grows on gravelly plains and flats in calcareous soil thickly strewn with smooth, white pebbles and which this Lithops resembles to an unbelievable degree, this camouflage allows them to escape detection and is a very effective strategy for escaping predation. They are pollinated by bees, flies, wasps, gnats, bugs and other insects that are common in the area.

• Lithops vallis-mariae C281 TL: 15 km E of Mariental, Namibia

• Lithops vallis-mariae (Dinter & Schwantes) N.E.Br.
• Lithops villetii var. deboeri (Schwantes) D.T.Cole
• Mesembryanthemum vallis-mariae Dinter & Schwantes
• Lithops vallis-mariae C060 30 km SSW of Mariental, Namibia
• Lithops vallis-mariae C066 20 km E of Gibeon Station, Namibia
• Lithops vallis-mariae C166 110 km NNE of Keetmanshoop, Namibia
• Lithops vallis-mariae C167 (syn. margarethae) TL: Near Berseba, Namibia
• Lithops vallis-mariae C182 125 km N of Keetmanshoop, Namibia
• Lithops vallis-mariae C238 85 km NE of Keetmanshoop, Namibia
• Lithops vallis-mariae C281 TL: 15 km E of Mariental, Namibia
• Lithops vallis-mariae C282 125 km North of Keetmanshoop, Namibia.
• Lithops vallis-mariae C296 40 km SSE of Koës, Namibia
• Lithops vallis-mariae var. margarethae (Dinter & Schwantes) N.E.Br.

• Lithops vallis-mariae cv. Valley Girl S.A.Hammer

Description: This peculiar species is characterised by a minutely pitted top surface, which appears uniform to the naked eye, consists in reality of a large number of ridges with vermiform convolutions. These peculiar vermiform ridges have the appearance of fine sintered limestone and only found in this species.
Habit: It is an acaulescent perennial, geophytic, succulent, seldom solitary, usually forming clumps of 2-4 head, occasionally with up 10 or more heads.
Bodies (Paired leaves): Medium sized, compact, obconic, truncate in profile, slightly convex; 25-40 mm long, 20-30 mm broad, fissure shallow, faces reniform, slightly rugose, opaque pale grey-white, or grey-white tinged with creamy yellow, green, beige or pink and very minutely wrinkled or dotted with pin-pricks. Top with many depressions, giving the appearance of a large number of dots or points. Margin and windows absent or very obscure or very opaque, yellowish-white to bluish-white. Islands manifest only as areas enclosed by channels. Channel often absent, very thin, sometimes quite deeply pitted, channels opaque to very obscurely translucent grey, bluish grey, pinkish grey or pinkish brown, Rub absent.
Flowers: Daisy-like, diurnal, small 15-30 mm in diameter, yellow, straw yellow, sometimes orange-yellow, may be tinged with bronze or pink.
Blooming season: Autumn (in habitat blooms in April)
Fruits: Mostly 5-chambered capsules, profile boat-shaped, flat, occasionally slightly convex, faces broadly elliptic.

Bibliography: Major refences and further lectures
1) Heidrun E. K. Hartmann “Aizoaceae F – Z” Springer 2002
2) Achim Hecktheuer “Mesembs, mehr als nur Lithops” Books on Demand GmbH Norderstedt. 2008
3) Desmond T. Cole & Naureen A. Cole, Uwe Beyer, Yves Delange “Les Lithops” SUCCULENTES Spécial 2008 AIAPS (now Terra seca). 2008
4) Desmond T. Cole & Naureen A. Cole “LITHOPS Flowering Stones” Cactus & Co. Libri. 2005
5) Yasuhiko Shimada “The Genus Lithops” Dobun Shoin. 2001
6) Rudolf Heine “Lithops - Lebende Steine” Neumann Verlag. 1986
7) Bernd Schlösser “Lithops – Lebende Steine” Praktische Anleitung für die Zimmerkultur. BussinessPoint MEDIA. 2000
8) Steven A. Hammer “Lithops – Treasures of the veld” British Cactus and Succulent Society. 1999
9) Desmond T. Cole “Lithops – Flowering Stones” Acorn Books 1988
10) Rudolf Heine “Lithops – lebende Steine” Neumann Verlag. 1986
11) David L. Sprechman “Lithops” Associated University Presses, Inc. 1970
12) Gert Cornelius Nel “Lithops” Hortors Limited, South Africa 1946
13) Edgar Lamb "The illustrated reference on cacti and other succulents" Blandford Press. 1978
14) Christopher Brickell, Royal Horticultural Society "RHS A-Z Encyclopedia of Garden Plants: K-Z., Volume 2" Kindersley, 2008
15) G. C . Nel “Lithops: Plantae succulantae, rarissimae, in terra obscuratae, e famailia Aizoaceae, ex Africa australi” Hortors Limited, Cape Town, South Africa 1946
16) Heidrun E. K. Hartmann "Illustrated Handbook of Succulent Plants: Aizoaceae F-Z" Springer, 2002
17) Steven A. Hammer "Lithops: Joyaux du veld" Editions Quae, 25/nov/2010
18) Doreen Court “Succulent Flora of Southern Africa” Struik Nature, 2010

Cultivation and Propagation: The Lithops (a.k.a. Living Stones) are some of the world's most fascinating plants and are sought by the collector of succulent plants. Paying attention to the particular growing requirement of Lithops is especially important. If you provide the Lithops with the right conditions, they will reward you with their unique shape, size, colour and a proliferation of blooms in autumn. However, Lithops are tricky plants that are very particular about their growing conditions and require the right maintenance in order to keep happy. But don't be afraid even the best growers have plants that mysteriously dry up, or leave during the night. While Lithops are picky about their care, if you are patient and remember the basics, your efforts will be rewarded. Being small plants, a representative collection can be grown on a patio table, a sunny windowsill or a shelf in the greenhouse.
Growing rate: Slow growing for a mesemb.
Soil: They grow best in an open mineral, sandy-gritty soil and requires good drainage as they are prone to root rot. They can grow outdoor in sunny, dry, rock crevices (protection against winter wet is required) They can also be cultivated in alpine house, in poor, drained soil.
Repotting: They may stay in the same pot for many years. Plants grown in larger containers have frequently relatively poor flowers. Flowers might improve when the plants are given their own, small individual pots.
Watering They Require little water otherwise the epidermis breaks (resulting in unsightly scars). The basic cultivation routine is: Stop watering after flowering. Start watering after the old leaves are 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. In the winter season the plant doesn’t need watering, the plant in this time extracts water from the outer succulent leaves, allowing them to shrivel away, relocating water to the rest of the plant and to the new leaves that form during this period. If grown in a container, bottom watering by immersing the container is recommended. Water sparingly only when warm, no water when cold. Nearly all problems occur as a result of overwatering and poor ventilation, especially when weather conditions are dull and cool or very humid. They must have very dry atmosphere.
Fertilization: Feed them once during the growing season with a fertilizer specifically formulated for cactus and succulents (high potash fertilizer with a dilute low nitrogen), including all micro nutrients and trace elements diluted to ½ the strength recommended on the label. They thrive in poor soils and need a limited supplies of fertilizer to avoid the plants developing excess vegetation, which is easily attacked by fungal diseases. Some growers fertilize frequently, some hardly ever. However, for the highly succulent mesembs, (Lithops, Conophytums, etc.) fertilization is not really necessary.
Light: They prefer a very bright situation and in winter they need the maximum amount of light you are able to give them, but keep more cool and partially shaded in summer. The only exception to this is seedlings in their first year that enjoy a shades place. Such tiny plants can easily get scorched or broiled and their appearance spoiled (this may not matter in the wild, where the Lithops have probably shrunk into the ground and becomes covered with sands). Outdoor (Lithops prefer full sun, with some shade in the hottest summer months. High levels of light are needed in autumn to flower and for good plant development. The low intensity of sun light during the growing season of this species generally prevents the white flower flowers from opening.
Special Advice: Lithops are best planted in a sunny and airy part of the greenhouse, and not too close to the glass roof or sides of the house as the plants can overheat during hot spells.
Hardiness: They require a minimum temperature 5°C (But will take a light frost and are hardy down to -7° C for short periods if they are in dry soil). USDA zones 9A – 11.
Uses: Container, rock garden.
Pests & diseases: Lithops may be attractive to a variety of insects, but plants in good condition should be nearly pest-free, particularly if they are grown in a mineral potting-mix, with good exposure and ventilation. Nonetheless, there are several pests to watch for:
- Red spiders: they may be effectively rubbed up by misting the vulnerable plants every day.
- Mealy bugs: occasianlly they develop aerial into the new leaves and flowers with disfiguring results, but the worst types develop underground on the roots and are invisible except by their effects.
- Sciara Flies: they are one of the major problems for seedlings. It is a good practice to mulch your seedlings with a layer of grit, which will strongly discourage the flies.
- Scales, thrips and aphids: (they are rarely a problem.)
It is wise to treat your whole collection with a systemic insecticide twice a year in spring and autumn.
- Rot: it is only a minor problem with mesembs if the plants are watered and “aired” correctly. If they are not, fungicides won't help all that much.
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".
Propagation: Seed or (or rarely) cuttings. The small seeds can be sown in pots of fine, well-drained sand, any time during the spring and summer months when temperatures are warm. Cover the seeds with a very fine layer of grit and water from below with a fungicide to prevent damping off. For the first 3-4 days cover the pots with a sheet of glass/clear perspex to keep the humidity levels high. Remove the glass and replace it with light shadecloth and mist once or twice a day for the next two weeks after which most seeds should have germinated. From then on mistings can be reduced to every second and then every third day as the little plants grow. Take the cuttings from a grown-up mother plant. Each cutting must contain one or more heads along with a fraction of root and permit them to dry out a couple of days, lay the cuttings on the soil and insert the stem end partially into the soil. Try to keep the cutting somewhat upright so that the roots are able to grow downward. It is relatively difficult to root Lithops from cuttings and generally pointless as well, so quick are they from seed.
Comment: Improvement of Lithops characteristics: Some growers (but not all!!) think it is very intriguing to reinforce any characteristic of cultivated Lithops of by crossing two similar selected plants and then back-crossing with the mother plant. This way we can eventually get some interesting results. Of course, many of the nicest Lithops we grow in cultivation have already been selected over time. However many Lithops are already nice plants which can’t really be improved, on the other hand one could try to improve the colour or the markings etc. Now if we have two particular plants we may attempt to breed between them and can maybe get a whole improved population and then select some better offspring to continue the selection.
Seed production: Plants can be hand pollinated, using a small paint brush. Remember always to cross different clones as the plants are self-sterile. The seed will remain viable for many years provided it is stored in a cool dry place.