Aloe calcairophila Reynolds
Limestone-loving aloe
Aloe calcairophila is a small aloe endemic to the western limestone karst of Madagascar, where it colonises crevices and fissures in calcareous rock with extremely well-drained and poor soils. Its epithet "calcairophila" reflects its unique affinity for calcareous substrates, setting it apart from most aloes that prefer acidic soils. Its orange-red tubular flowers emerge on slender peduncles during the dry season.
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Overview
| Category | Classification |
|---|---|
| Family | Asphodelaceae |
| Genus | Aloe |
| Growth Habit | Small rosette, solitary or in sparse clusters |
| Conservation Status | Endangered |
| pH Target | 7.5–8.5 |
| Type | Calcareous lithosol, extremely porous and poor |
Origin & Habitat
Morphology
Lanceolate leaves 15–25 cm long, grey-green with faint longitudinal lines, white marginal teeth 1–2 mm and a slightly tuberculate surface.
ecoPractically stemless; the rosette sits directly on limestone exploiting minimal soil accumulations.
ecoTubular flowers 2.5–3 cm long, orange-red, in simple racemes on slender 30–50 cm peduncles. Flowering in the dry season.
ecoFine contractile roots penetrating limestone fissures to anchor the rosette and extract water in lithosolic soils.
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Requirements
Soil & Substrate
Type
Calcareous lithosol, extremely porous and poor
groups Beneficial Associations
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Propagation Strategy
- 1 Sow in highly porous calcareous substrate at 24–28 °C.
- 2 Keep slightly moist with spray and cover with clear film.
- 3 Germination in 3–6 weeks; gradually remove film.
- 4 Seedlings are delicate; transplant very carefully at 3–4 cm.
- 1 Separate sparse offsets with a clean knife during the warm season.
- 2 Allow to callus for 3–4 days in a very dry environment.
- 3 Plant in calcareous gravel with minimal initial watering.
- 4 Root in 6–9 weeks.
Replicate the natural habitat: calcareous substrate, full sun and prolonged drought.
Frequent watering, fatal for this ultra-xerophytic species.
Every 4–5 years; handle with gloves due to spines
No regular fertilisation; optionally one minimal dose of alkaline mineral fertilizer in spring
Uses & Applications
Precautions / Toxicity
Toxic if ingested; spines cause physical injury. Keep out of reach of children and pets.
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"A. calcairophila is one of the few aloes in the world with documented preference for alkaline calcareous substrates; most of the genus tolerates or prefers acidic soils, making its root biochemistry and micronutrient absorption at high pH an active area of research."
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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.