4.2. Senna Meridionalis 7694

🌿 Senna meridionalis (commonly known as the Taraby plant or Madagascar Bonsai Senna, and historically classified under the basionym Cassia meridionalis) is an extraordinary, pachycaul caudiciform shrub or small tree in the legume family, Fabaceae. It is endemic to the arid southern and southwestern regions of Madagascar, particularly across the calcareous limestone plains, spiny thickets, and dry deciduous forests surrounding Toliara and the Mahafaly plateau. In its native habitat, it endures blistering tropical heat, poor stony soils, and prolonged dry seasons by storing moisture and vital nutrients within a swollen, succulent trunk base and gnarled, zig-zagging branches. It is a premier collector-level houseplant, revered by succulent enthusiasts and bonsai connoisseurs for its naturally sculpted silhouette, delicate pinnate leaves, and bright yellow blossoms.
FUN FACT
Senna meridionalis forms a distinctive pachycaul architecture where the plant can grow up to 60 centimetres with a stem of fourteen centimetres.
FOLIAGE AND GROWTH HABIT
Senna meridionalis develops a swollen, pachycaul caudex that forms an impressive basal trunk, reaching up to 14 centimetres in thickness while the plant typically attains 40 to 60 centimetres in height in indoor container culture. In wild habitat, mature specimens can develop into stout shrubs up to 2 metres tall over many decades. The trunk is cloaked in smooth to finely fissured, pale silvery-grey to buff-brown bark that displays attractive textural character with age. Radiating from the main trunk is an intricate framework of stiff, zig-zagging, angular branches with very short internodes. Arranged alternately along the twigs are small, paripinnate compound leaves measuring 1.5 to 3 centimetres in total length. Each leaf blade comprises 4 to 8 pairs of tiny, opposite, obovate to oblong leaflets that measure only 3 to 6 millimetres across. The leaflets are smooth, leathery, and dark emerald-green. Notably, the foliage displays fascinating nyctinastic sleep movements: each evening at dusk or during heavy overcast weather, the paired leaflets fold upward and press tightly against each other, reopening fully when morning light returns.
FLOWER DETAILS
Flowering takes place during late spring and summer on mature, sun-ripened branches. The inflorescences emerge from upper leaf axils, bearing solitary or clustered blossoms held on short, slender pedicels. Each flower measures approximately 1.5 to 2.5 centimetres in diameter and features five spreading, rounded, golden-yellow petals that contrast vividly against the dark green miniature compound foliage. At the center of the blossom are ten fertile stamens of varying lengths capped with prominent pollen-bearing anthers. The flowers open fully during bright midday warmth—an attribute reflected in the specific epithet meridionalis, meaning of noon or mid-day in Latin—and remain receptive for several days. After successful insect pollination, the flowers give way to slender, flattened, brownish legume pods containing several hard, disc-shaped seeds.
CARE INSTRUCTIONS
🌞 Light: Demands full, unfiltered direct sunlight for 6 to 8 hours daily. A south-facing or southwest-facing exposure is essential to maintain dense ramification, prevent leggy internodal stretching, and stimulate the production of flower buds.
💧 Water: Employ a strict soak-and-dry irrigation approach. During the active spring and summer growing season, water thoroughly only after the potting substrate has dried out completely. In autumn, as daylight decreases and the plant naturally sheds foliage for winter dormancy, reduce watering drastically, offering only a small sip once every 4 to 5 weeks to prevent root dieback.
🌡️ Humidity: Prefers low to moderate indoor ambient humidity between 25% and 45%. It tolerates dry household air generated by Canadian winter heating systems with great ease, provided adequate ventilation is maintained.
🪴 Soil: Requires an ultra-porous, gritty mineral potting blend composed of 70% to 75% inorganic aggregates (pumice, crushed volcanic lava scoria, coarse perlite, and coarse granite grit) blended with 25% to 30% low-organic cactus potting compost.
🏺 Potting: Best planted in a shallow, unglazed terracotta pot or wide ceramic bonsai tray equipped with multiple large drainage holes. The wide container provides physical balance for the heavy pachycaul trunk while porous clay facilitates rapid root aeration.
🌱 Growth rate: Very slow grower, adding only a few centimetres of branch extension and gradual trunk girth each growing season, making it an enduring living sculpture.
👩‍🌾 Fertilizing: Feed once a month from May through August using a balanced, low-nitrogen liquid houseplant fertilizer diluted to one-quarter strength. Cease all fertilization completely from September through early spring.
WHERE TO PUT IT
Senna meridionalis is an outstanding focal specimen for a sun-drenched windowsill, dedicated bonsai display bench, or bright conservatory table where its architectural branching can be showcased. Maintain indoor ambient temperatures between 20°C and 30°C during active summer growth, and ensure winter resting temperatures remain safely between 12°C and 16°C. Position the container away from cold drafty exterior doors, air-conditioning currents, and high-humidity terrariums. Prune carefully in early spring to shape the miniature canopy according to classical bonsai principles.