Argyroderma testiculare Photo by: Valentino Vallicelli
Origin and Habitat: Vanrhynsdorp District, Western Cape, South Africa.
Altitude range: 120 - 400 metres above sea level.
Habitat and ecology: This species grows on quartz flats, among pebbles.
Synonyms:
Description: Argyroderma testiculareSN|33232]]SN|33229]] is a dwarf, compact, perennial succulent, reduced to a single leaf-pair, sometimes branched, and forming short columns. The older leaf-pairs persist, and remain yellow for some time, and become black later.
Derivation of specific name: Latin “testicularis”, “testiculare”, Shaped like testicles.
Leaves: Paired and appressed, half-ovoid, distinctly keeled, 25-35 mm long,15-25 mm broad, separated by 4-10 mm gap at the apex, dark green, yellow and eventually black with age, the old leaf-pairs forming a tight persistent bowl around the base of the foliage leaves. Flower colour often varies between populations and sometimes even within a population.
Flowers: Single, almost stalk-less or very short stalked, bracteolate, 25-35 mm in diameter, deep purple, rarely pink, white or yellow, inner petals often shorter. Argyroderma species are obligately outcrossing and flowers are pollinated primarily by small solitary bees
Blooming season: Argyroderma begin blooming the rainy season (winter rains) starts, developing their fruits and new leaves during the rains. In habitat flowering starts in April, in northern hemisphere mostly in Augusts.
Fruits (hygrochastic capsules): Long stalked with a rounded, apically narrowed base and an oblique, longish hypanthium, the bracteoles not touching the base of the capsule, locules 12-18. The fruits are persistent on the parent plant.
Seeds: Smooth, brown.
Chromosome number: 2n = 18.
Note: In growth and leaf form, the species resembles Argyroderma pearsoniiSN|33229]]SN|33232]], differing mainly in the yellow old leaves, the keel, and the brighter flowers with a strikingly dense petal arrangement in many populations resulting in a beautiful show.
Bibliography: Major references and further lectures
1) Heidrun E. K. Hartmann“Aizoaceae A – E” Springer (2001)
2) Lorraine Harrison “Latin for Gardeners: Over 3,000 Plant Names Explained and Explored” University of Chicago Press, 21 September 2012
3) James Cullen, Sabina G. Knees, H. Suzanne Cubey “The European Garden Flora Flowering Plants: A Manual for the Identification of Plants Cultivated in Europe, Both Out-of-Doors” Cambridge University Press, 11/Aug./2011
4) ALLAN G. ELLIS, ARTHUR E. WEIS, AND BRANDON S. GAUT "EVOLUTIONARY RADIATION OF ‘‘STONE PLANTS’’ IN THE GENUS ARGYRODERMA (AIZOACEAE): UNRAVELING THE EFFECTS OF LANDSCAPE, HABITAT, AND FLOWERING TIME" Evolution, 60(1), 2006
Cultivation and Propagation: Argyroderma is easy to grow. Argyroderma are more forgiving than Lithops of excess water (though it should be rarely given in summer) and thrive in light winter rains in temperate climates and were heading for summer dormancy.
Soil requirements: It needs a very draining mineral, rather acidic, substrate. A mixture comprising 20 % pumice grit, 20% lava grit, 20% quartz grit, 20% coarse river sand and 20 % garden soil seems well suited.
Water needs: Requires little water otherwise its epidermis breaks (resulting in unsightly scars). Water minimally in summer, only when the plant starts shrivelling. But be careful with watering (rot sensitive).
Fertilization: Fertilize moderately during the growing season with diluted high potassium fertilizer.
Hardiness: It is fairly cold resistant and hardy to -5°C (or less if dry) depending on the clone.
Exposure: Need full sun, (with insufficient illumination bodies get thinner as a result of the lack of sun) but keep cool and shaded in summer,
Propagation: Seeds or division of larger clumps. Argyroderma is very easy to start from seed. Seeds germinate in 7-14 days at 21°C. Although they will start from cuttings, it is quite difficult to get them to root. If they start to rot there is usually part of the plant that can be removed and possibly rooted.
