Adansonia rubrostipa
Red-stalked baobab
Adansonia rubrostipa, known locally in Madagascar as 'fony', is the smallest baobab in the genus and the only one adapted to growing in pure sandy soils and coastal dunes. Endemic to the arid zones of southwestern Madagascar, it is distinguished by its bulbous, stocky trunk of reddish-orange color (hence its epithet 'rubrostipa', 'red stalk'), its low stature compared to other baobabs, and its extraordinary resistance to salinity and extreme desiccation. It is a highly valued species in botanical collections for its compact silhouette and adaptation to extreme conditions.
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© Olivier Lejade
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Overview
| Category | Classification |
|---|---|
| Family | Malvaceae |
| Genus | Adansonia |
| Growth Habit | Low to medium-sized deciduous tree with a markedly bulbous trunk and sparse crown. The trunk can be wider than tall in old specimens. Very slow growth. |
| Conservation Status | Vulnerable (VU) according to the IUCN. Threatened by sand extraction from the coastal dunes it inhabits, excessive grazing, and climate change accelerating desertification. |
| pH Target | 6.5–8.0 |
| Type | Pure or near-pure sand, very permeable, nutrient-poor, with tolerance to light salinity. |
Origin & Habitat
Morphology
Markedly bulbous and short trunk, reddish-orange or reddish-brown in color with gray patches. The bark is smooth and shiny, especially striking at the base. The bottle-shaped form and reddish color are the most distinctive features of the species and give it a succulent caudex appearance.
ecoDigitate leaves with 5–7 narrow and lanceolate leaflets, grayish-green in color. They are smaller and narrower than those of other species in the genus, as an adaptation to reduce transpiration in its extremely arid and saline environment.
ecoMedium-sized white flowers (8–14 cm in diameter) with characteristic reflexed petals. As in the entire genus, they open at dusk and are short-lived (one night). The peduncle is long and pendulous. Pollination in its habitat is carried out mainly by bats and moths.
ecoSmaller fruits than other species in the genus (10–18 cm), ellipsoid to globose in shape, with a thin woody shell. The dry pulp contains small seeds embedded in reddish-orange fiber, which contrasts with the white pulp and is characteristic of the species.
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Requirements
Soil & Substrate
Type
Pure or near-pure sand, very permeable, nutrient-poor, with tolerance to light salinity.
groups Beneficial Associations
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Propagation Strategy
- 1 Use fresh seeds less than 2 years old. Viability decreases rapidly over time.
- 2 Scarify the seed coat with 80-grit sandpaper, sanding in one direction until the whitish cotyledon is visible in backlight.
- 3 Soak in mineral water at room temperature for 12–24 hours. Seeds that float after 24 hours are discarded.
- 4 Sow in pure quartz sand (not garden substrate) in shallow trays. Cover with 0.5 cm of sand.
- 5 Maintain at 30–38 °C with light misting once a day. Avoid waterlogging.
- 6 Germination in 1–3 weeks. Seedlings are more robust than those of other species in the genus from the first months.
- 7 Transplant individually when seedlings are 5–8 cm tall, using pure sand with 10% added perlite.
It is the most pot-cultivation-adapted species in the genus: its compact final size allows it to be kept indoors with full south-facing window sun.
Using organic substrate or garden soil: it retains too much moisture and rots the caudex.
Every 3–4 years or when roots emerge through drainage holes. Repot at the beginning of spring, before budding.
Very moderate fertilization: one monthly application with cactus and succulent fertilizer (low-nitrogen formulation) during active growth months (May–August). Never fertilize during dormancy.
Uses & Applications
Precautions / Toxicity
No known toxicity. The fruit pulp is consumed locally by people and wild animals without documented adverse effects.
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Plant Health
Rot from excess moisture: this is the most serious threat in cultivation. The bulbous trunk softens and collapses quickly if the substrate retains moisture. Treatment is exclusively preventive: pure sand as substrate and zero watering during dormancy.
Spider mites (Tetranychus urticae): in dry indoor environments, mites can colonize foliage causing bronze stippling and defoliation. Treatment: temporarily increase ambient humidity and apply systemic acaricide (abamectin).
Superficial bark discoloration: white or gray spots on the trunk caused by lichens or algae under conditions of excess ambient humidity. No vital risk. Treatment: improve ventilation and sun exposure.
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"A. rubrostipa is the favorite among caudiciform collectors thanks to its bright red bulbous trunk that resembles a terracotta bottle. It adapts better to pot cultivation than other species in the genus, given its smaller final size. It is ideal for large-scale bonsai ('fat trunk bonsai'). Its tolerance to some salinity makes it an interesting candidate for gardening projects in Mediterranean coastal areas."
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Scientific Integrity
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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.