Alluaudia montagnacii Rauh
Montagnac's alluaudia
Restricted to the southernmost tip of Madagascar, around Cape Santa Maria. Named after the collector Montagnac. Produces distinctively horizontal to ascending branching patterns different from the more vertical A. ascendens. Especially threatened by its extremely restricted distribution.
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Overview
| Category | Classification |
|---|---|
| Family | Didiereaceae |
| Genus | Alluaudia |
| Growth Habit | Columnar succulent shrub or tree with horizontal to ascending branching |
| Conservation Status | Vulnerable to Endangered; extremely restricted distribution at Cape Santa Maria, Madagascar |
| pH Target | 7.0–8.5 |
| Type | Coastal calcareous sand or alkaline mineral substrate |
Origin & Habitat
Morphology
Small, oval, 6–14 mm, succulent and glossy; shed in the dry season; emerging in groups at the spiny nodes of the stems.
ecoErect main stem 3–7 cm diameter with markedly horizontal to ascending lateral branching; paired spines 1–2.5 cm on prominent tubercles.
ecoVery small, unisexual (dioecious) flowers, greenish; grouped in short terminal clusters during the wet season (November–January in the Southern Hemisphere).
ecoRoot system adapted to the sandy and calcareous coastal soils of southernmost Madagascar; extensive shallow roots to capture sparse rainfall.
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Requirements
Soil & Substrate
Type
Coastal calcareous sand or alkaline mineral substrate
groups Beneficial Associations
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Propagation Strategy
- 1 Cut a stem section of 20–35 cm in the middle of summer.
- 2 Allow the cut to callous for 2–3 weeks in a warm dry environment.
- 3 Plant in pure calcareous sand with very little initial watering.
- 4 Roots may take 8–12 weeks; do not move or over-water.
- 1 Difficult to obtain seeds outside Madagascar; use fresh material if possible.
- 2 Sow in calcareous sand at 28–32 °C.
- 3 Very irregular germination between 3 and 16 weeks.
- 4 Seedlings are extremely sensitive to excess moisture.
This is the most demanding Alluaudia; reserved for experienced collectors.
Any watering in winter, absolutely fatal for this species.
Only when strictly necessary; every 5–7 years at most
No fertilisation in winter; a minimal cactus feed (1/8 dose) only once in summer
Uses & Applications
Precautions / Toxicity
Sharp spines represent physical hazard. Sap mildly irritating on contact with sensitive skin.
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"A. montagnacii is one of the least studied Didiereaceae. Its horizontal branching pattern differentiates it ecologically from the rest of the genus, possibly as an adaptation to the strong sea breezes of Madagascar's southernmost cape."
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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.