Adromischus marianiae (Marloth) A.Berger
Mariana's Adromischus
Adromischus marianiae is considered by collectors as the jewel of the genus, with multiple forms and varieties (alveolatus, herrei, hallii, immaculatus) showing extraordinary morphological diversity in texture, color, and leaf shape. It is native to the Northern Karoo and South African Namaqualand, growing in quartz and granite rock crevices. The variety alveolatus, shown in the selected image, is especially coveted for its tuberculate leaves of volcanic appearance.
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© Crystal Buchanan Falck
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Overview
| Category | Classification |
|---|---|
| Family | Crassulaceae |
| Genus | Adromischus |
| Growth Habit | Compact plant 4–12 cm; very slow branching; very short stem; forms dense clumps over time. |
| Conservation Status | Not assessed as species; some forms (herrei, alveolatus) have pinpoint-restricted distributions with potential risk from illegal over-collection. |
| pH Target | 5.0 – 6.5 |
| Type | Quartzitic or granitic, ultra-acidic to neutral, virtually no organic matter. |
Origin & Habitat
Morphology
Enormously variable by variety — ovate to clavate (2–5 cm), with surfaces ranging from smooth (var. immaculatus) to deeply tuberculate (var. alveolatus); colors from green to dark red, brown, or garnet; no farina in most forms; in var. alveolatus texture rough as lava.
ecoVery short stem (1–3 cm) to subacaulescent; scarce branching; in var. herrei stems may be somewhat more robust.
ecoErect spike 15–30 cm; tubular flowers white-pink to pinkish-violet with dark streaks; summer flowering.
ecoVery thin and sparse roots, adapted to quartz crevices with almost no soil; one of the least developed root systems in the genus.
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Requirements
Soil & Substrate
Type
Quartzitic or granitic, ultra-acidic to neutral, virtually no organic matter.
groups Beneficial Associations
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Propagation Strategy
- 1 Select a leaf with well-developed warty tubercles; remove with gentle rotary traction, avoiding damage to the tubercles
- 2 Rest in a ventilated, dry, lightly shaded spot for a minimum of 3 days; A. marianiae is very slow, so complete callousing is essential
- 3 Position the leaf on rough mineral substrate (crushed granite + perlite) with the cut end just touching the surface
- 4 Water very sparingly (every 10–14 days); expect 5–8 weeks before seeing first roots due to the species' very slow growth rate
- 1 Sow on the surface on very fine mineral substrate; do not cover seeds with substrate
- 2 Cover with glass or film and keep at 22–25 °C; expect 3–5 weeks to germinate given the species' slow rate
- 3 Ventilate daily for a couple of minutes starting in the second week
- 4 Transplant with extreme care when seedlings are 2 cm; the root system is fragile
This is one of the slowest species in the genus; do not compare its pace with other succulents
Growing impatient with slow growth and overwatering, thinking the plant is stressed
Every 3–4 years in spring; handle with padded tweezers to avoid damaging the tubercles.
No regular fertilizer; if desired, apply very diluted mineral fertilizer (10% of dose) just once in spring.
Uses & Applications
Precautions / Toxicity
No known toxicity for humans or domestic animals; no irritant compounds reported.
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"The forms of A. marianiae have been the subject of one of the greatest taxonomic debates in the genus: authors like Toelken maintain them as varieties of a single polymorphic species, while others propose elevating them to independent species. DNA analysis published in 2018 suggests herrei and alveolatus are genetically differentiated but not to the level of full species."
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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.