Description: Pachypodium baronii 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 baronii subs. windsorii. Unfortunately, in the wild it is rare and local, being recorded from only two small areas in the north of Madagascar, Pachypodium baronii 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 baronii 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
Cultivation and Propagation: Pachypodium baronii 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.