Origin and Habitat: North Madagascar; local endemic. Befandriana Nord to Mandritsara.
Altitudinal range: 300-1200 metres above sea level.
Habitat and ecology: They grows on steep gneiss and granite rocks rocks. Mostly in full sun, sometimes in open dry deciduous forest in light shade where they take advantage of micro-environments suitable for succulents. Accompanying species can be Pachypodium sofienseSN|14822]]SN|14822]], Uncarina sp., Aloe bulbilliferaSN|31880]]SN|31880]], Euphorbia miliiSN|23360]]SN|23360]], Kalanchoe gastonis-bonnieriSN|27797]]SN|27797]], Urera sp. and Ischnolepis sp.

• Pachypodium baronii Costantin & Bois

• Pachypodium baronii Costantin & Bois
• Pachypodium baronii var. erythreum Poiss.
• Pachypodium baronii var. typicum Pichon

• Pachypodium baronii subs. windsorii (Poiss.) Pichon
• Pachypodium windsorii Poiss.

Description: Pachypodium baroniiSN|14804]]SN|14804]] is a succulent shrub with robust, globose to bottle-shaped trunk (caudex), much branched, up to 2 (or more) m high. This species produces spectacular red flowers with a white eye in the centre and each lasts for several days. This species is relatively rare in cultivation, but is greatly appreciated and cultivated by sophisticated succulent fanciers and caudiciform collectors worldwide. Two subspecies are recognized, the nominate form and Pachypodium baroniiSN|14804]]SN|14804]] subs. windsorii. Unfortunately, in the wild it is rare and local, being recorded from only two small areas in the north of Madagascar, and the type locality of var. windsorii has been almost cleaned out by ruthless collectors.
Stem (caudex): Globose to broadly flask-shaped, thickened base 20-40 cm in length by 20-50 cm in diameter, tapering off above into a few, thick, elongated, stout ascending branches sparingly forked towards the tips 30-50 cm long, 4-8 cm in diameter, tapering to 3 cm in diameter. Pachypodium baroniiSN|14804]]SN|14804]] typically grows to 0.5-2(-3.5) metres high. Epidermis pale grey or grey-green smooth, sometimes with remnants of leaf scars. Branchlets are 1.5 -7 cm long and 0.8-1.5 cm in width and covered all over in stiff spines.
Spines: Paired, broadly conical, often curved, stiff, (2-)6-8(-9) mm long to 1-4 mm in diameter at the base. The spines are often red and pubescent, hairy when young, turning brown and glabrous and smooth.
Leaves: Loosely clustered towards the tips of the stems, elliptic to oblanceolate, 9-15 cm long, 4.5-6 cm wide, leathery, and medium green, pubescent below, shortly petiolate. Petiole pale reddish-green, pubescent, approx 3-25 mm long. Apex acute to acuminate with a soft shiny tip.The pale green midrib and dark green reticulate venation is visible when the blade is fresh.
Inflorescences: Pedunculate 3-17-flowered, 16-40 cm in length and to 4.5-12 cm across. Peduncle pale green, glabrescent and terete, 4-25 cm long, 4-6 mm wide. The pedicels are pale reddish-green, 8-23 mm long, and sparsely pubescent and hairy. Bracts oblong 5-11 mm long, 2-2.5 mm wide and longer than the sepals.
Flowers: Showy, salverform, bright red with a white eye, narrow-tubed, 5-6 cm in diameter and about 5.5 cm long. Sepals dark green, glabrous, smooth, persistent until maturity of the flower, narrowly ovate-acuminate at the apex , 2.5-6 mm long, 1.5-2.5 mm wide. Buds acuminate, tapering gradually to a sharp point, to obtuse. Corolla lobes broadly obovate, 15-19 mm long, 11-17 mm wide, rounded at apex and ciliate at the margin. The mouth is more densely pubescent and hairy. Tube 15-23 mm long,almost cylindrical, but often conically widened at the base, the upper part is almost cylindrical and slightly narrowed at the mouth. Stamens 1-1.4 cm long. Anthers very narrowly triangular 6-6.5 mm long,1-1.3 mm wide. Style 9-11 mm long with a stigmoid apex 0.1-0.2 mm by 0.3-0.4 mm. Disk composed of five unequal glands, where 2 or 2 pairs are fused partly or entirely. Ovary 2-2.5 mm long, 1.8-2.2 mm wide, pubescent on the part not covered by the disk. The ovules are approximately 50 in each carpel.
Blooming season: Flowers appear profusely over a long season from spring throughout the summer.
Fruits: The fruit is a twin horn-like cylindrical follicle (or mericarps), spindle-shaped, either straight or recurved, attenuate at the apex, small, about 4-11 cm long, 9-20 mm wide, 7-10 mm thick, pale reddish-green with longitudinal lines when fresh and when dried pale brown to pale greenish-brown to dark brown outside and whitish to very pale brown inside. Wall 1 mm thick.
Seeds Ovate to elliptic 6-7 mm long, pinkish brown.

Bibliography: Major references and further lectures
1) S. H. J. V. Rapanarivo “Pachypodium (Apocynaceae)” CRC Press, 01/Jun/1999
2) Werner Rauh “The Wonderful World of Succulents: Cultivation and Description of Selected Succulent Plants Other Than Cacti” Smithsonian Institution Press, 1984
3) Werner Rauh, Herman Schwartz “Succulent and xerophytic plants of Madagascar” Volume 2 Strawberry Press, 1998
4) G. D. Rowley: Pachipodium. In: Urs Eggli: "Illustrated Handbook of Succulent Plants: Dicotyledons." Springer Verlag, 2002
5) G. D. Rowley “Pachypodium & Adenium.” in: Cactus File, Cirio Pub. Services, 5: 1-79. 1999
6) Urs Eggli, Newton L.E. & Rowley G.D., CITES "Aloe and Pachypodium Checklist", Board of Trustees of the Royal Botanic Gardens, Kew, 2001
7) Urs Eggli “Illustrated Handbook of Succulent Plants: Dicotyledons” Springer Science & Business Media, 2002
8) Wikipedia contributors. "Pachypodium baronii." Wikipedia, The Free Encyclopedia. Wikipedia, The Free Encyclopedia, 9 Sep. 2015. Web. 15 Sep. 2015.

Cultivation and Propagation: Pachypodium baroniiSN|14804]]SN|14804]] is one of the most attractive species in the entire genus that can be grown both indoors, as well as outdoors in warm climates. It’s a rare and slow growing species and an impressive caudex can be developed over the years. In the winters it is deciduous. Pretty cold sensitive- supposedly prone to rot if wet in winter cold. It may be grown as a specimen among rocks and low-growing plants in a hot rockery. It may also be grown in a heavy container on the sunny patio.
Soil: Needs a gritty, porous cactus potting mix with peat gneiss sand, pH 4-5. It needs larger pot sizes than other species.
Watering: Water sparingly in the heat of the growing season to encourage new growth, foliage and flowering, and give extra well-drained soil to avoid waterlogged conditions, no water from late autumn to mid-spring. The watering program will change depending on temperatures and stage of growth, but it is best not to let this plant dry out completely for any length of time. Indoors it is best to keep it on the dry side, or it is prone to rot. Outdoors it must be protected from the rain in winter. Do not let this specimen sit damp in cool weather. The older it gets the less water it must receive!
Hardiness: It is sensitive to cold and should be kept totally dry in winter .Temperature from spring to autumn: nocturnal 12°C and diurnal up to 40°C. Wintering: nocturnal 12°C and diurnal 20°C or more, but it demonstrates some cold resilience if dormant and the soil is bone dry in winter. Protect from frost. It tends to lose its leave and go dormant in winter (USDA Hardiness zones: 10 – 11).
Exposure: It like full sun to light shade.
Maintenance: This Pachypodium will not require any pruning to look like a very interesting and unusual bonsai, but after several years it can outgrow its indoor location, requiring a 'pruning'. It has amazing regenerative properties.
Repot: Repot the plant every 3 years; this is quite tricky given all the spines. The best way is to wrap several layers of newspaper around the trunk where it is to be handled.
Warning: This plant has spines use caution when handling.
Propagation: Seeds or (rarely) cuttings. Fresh seeds results in a remarkable yield of new plants, perhaps 90% and seedlings grow fairly easily. Soak seeds in warm water for 24 hours before sowing in a 5 mm deep, sterile, moist sandy medium (4 parts fine and 4 parts coarse river sand 1 part sieved, well-rotten compost; 1 part perlite; 1 part vermiculite. Keep the mix moist and at a temperature of 27–35°C to ensure rapid germination. Seed start sprouting in just 3-4 days ( but continue to germinate erratically for about 6 month) they are also propagated by removal of branches from old plant (if they need to be pruned). They should be allowed to dry for 5 to 8 days before potting up, however the cuttings often fail to root. Seedlings grow fairly slowly compared to other Pachypodium species. Young plants have more conical spines and begin early to swell nicely, branch and even flower. It can flower when it is 4 years old.