Argyroderma pearsonii (N.E.Br.) Schwantes
Pearson's Silverstone
Argyroderma pearsonii, "Pearson's Silverstone," is a mesemb from the quartz fields of the South African Western Cape, described in honor of botanist Harold W. Pearson, first director of Kirstenbosch Botanic Garden. It is distinguished by its unusually dark violet-magenta or deep red flowers for the genus, and its grey-green to blue-grey leaves.
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Overview
| Category | Classification |
|---|---|
| Family | Aizoaceae |
| Genus | Argyroderma |
| Growth Habit | Acaulescent perennial succulent with 1–2 pairs of globose leaves; can branch and form small clumps. Active autumn–winter growth. |
| Conservation Status | Least Concern (LC) at IUCN level; like all Argyroderma, vulnerable to illegal collection and mining in the Knersvlakte. |
| pH Target | 6.5 – 7.5 |
| Type | Western Cape quartz fields; pure quartz, no organic matter, neutral to slightly acidic pH. |
Origin & Habitat
Morphology
Very succulent, globose leaves, grey-green to blue-grey, with smooth, waxy surface. Somewhat more compact and rounded than A. fissum; the central fissure is visible but not very pronounced. They measure 3–5 cm in diameter per pair.
ecoPractically invisible; emerges directly from the quartzitic substrate. Can develop a small caudex in mature plants.
ecoDark violet-magenta to wine-red flowers, 3–4 cm in diameter; the dark petal tone is the most distinctive diagnostic feature of the species. They bloom in autumn–winter during peak sunlight hours.
ecoThick, fleshy vertical roots; similar to the rest of the Argyroderma genus.
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Requirements
Soil & Substrate
Type
Western Cape quartz fields; pure quartz, no organic matter, neutral to slightly acidic pH.
groups Beneficial Associations
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Propagation Strategy
- 1 Sow in autumn when overnight temperatures drop below 20 °C; A. pearsonii needs autumn coolness to germinate properly
- 2 Use very fine quartz sand as the sole substrate; distribute seeds on the surface without burying
- 3 Keep under a glass cover with gentle misting every 2–3 days; do not waterlog the seedbed
- 4 Germination in 1–3 weeks; the characteristic purple-magenta flowers are only seen on mature plants of several years
- 1 Divide in autumn when the purple flowers appear or are about to appear; never divide in summer under any circumstances
- 2 Separate each pair of smooth leaves with a scalpel, keeping the roots intact in each division
- 3 Callous for 2–3 days before planting; each leaf pair forms an independent propagation unit
- 4 Plant in pure sand; wait to see movement in the leaves before watering (3–5 weeks)
A. pearsonii is known for its purple-magenta flowers; flowering requires strict seasonal drought/moisture cycles
Watering in summer upon seeing yellow or wrinkled leaves, causing irreversible rot
Every 4–5 years in autumn; disturb as little as possible, as it is sensitive to root disturbance.
No fertilizer for the first 3 years; after that, minimal mineral fertilizer (10% dose) once in October. Never in summer.
Uses & Applications
Precautions / Toxicity
No reported toxicity; consistent with genus profile.
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"A. pearsonii's flowers are notably darker compared to the rest of the genus; a pollination hypothesis proposes that the dark violet color may attract pollinators sensitive to longer wavelengths that predominate under the light conditions of the Knersvlakte quartz fields. This would make A. pearsonii a case of adaptation to a specific pollination niche within the genus."
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Scientific Integrity
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Sources
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Discussion
Disclaimer
This species record is provided for educational and informational purposes only. Jardín Roca Negra does not guarantee the accuracy or completeness of the data. Content is community-curated and may be subject to revision; it should not replace advice from a qualified botanist. This species may be toxic, invasive, or subject to legal restrictions — verify before handling or cultivating. Jardín Roca Negra accepts no liability for any harm arising from reliance on this information. Images are reproduced under Creative Commons or equivalent free licenses; credits are noted below each image.