Alluaudia ascendens (Drake) Drake
Ascending alluaudia
Columnar succulent endemic to the spiny forest of southern Madagascar. Forms slender, erect stems with paired spines and small oval deciduous leaves. Can reach 6–12 m in the wild. Dioecious (separate male and female plants). Adapted to the extreme seasonal drought of the Toliara spiny forest.
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Overview
| Category | Classification |
|---|---|
| Family | Didiereaceae |
| Genus | Alluaudia |
| Growth Habit | Columnar succulent shrub or tree, erect spiny stem with paired spines, deciduous |
| Conservation Status | Vulnerable; threatened by destruction of Madagascar spiny forest for charcoal and agriculture |
| pH Target | 6.5–8.0 |
| Type | Stony arid mineral substrate, no organic matter |
Origin & Habitat
Morphology
Small, oval to orbicular, 5–15 mm, succulent, deep green; deciduous in the dry season; emerging in pairs from tubercles beside the spines.
ecoColumnar stems, slender, 3–8 cm diameter, grey-green, densely covered with 1–3 cm spines in pairs emerging from helical tubercles.
ecoVery small, greenish to whitish, unisexual (dioecious plant); grouped in small terminal cymes during the wet season.
ecoDeep branched root system adapted to the stony soils of the spiny forest; capable of extracting moisture in conditions of extreme aridity.
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Requirements
Soil & Substrate
Type
Stony arid mineral substrate, no organic matter
groups Beneficial Associations
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Propagation Strategy
- 1 Cut a 20–40 cm stem in summer using a sterilised tool.
- 2 Allow the cut to dry in a warm dry place for 1–2 weeks.
- 3 Insert in dry mineral substrate and begin watering minimally after 3–4 weeks.
- 4 Roots emerge in 4–8 weeks; avoid moving the pot during this period.
- 1 Use fresh seeds (viability decreases rapidly).
- 2 Sow in sandy substrate at 25–30 °C with minimal moisture.
- 3 Germination is irregular: may occur between 2 and 12 weeks.
- 4 Seedlings are very slow; maintain warmth and intense light.
Water mainly in summer (May–September in cultivation); reduce drastically in winter.
Watering in winter, causing rot at the base of the stem.
Every 3–5 years in summer when roots outgrow the pot
Very diluted mineral fertilizer (1/4 dose) once in spring and once in summer
Uses & Applications
Precautions / Toxicity
Spines are a physical hazard; sap may cause mild irritation on sensitive skin. Handle with gloves.
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"The spiny forest of southern Madagascar is one of the most unique ecosystems on the planet, with over 90% of its plant species endemic. A. ascendens is one of its dominant structural elements, acting as a 'nurse tree' for many other understorey 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.