Boswellia nana
| Light | Full sun to very bright light; the more light, the tighter the growth |
|---|---|
| Water | Regularly in leaf during warm months; taper off as it drops its leaves, keep dry through winter dormancy |
| Soil | Very fast-draining, gritty mineral mix (see Soil and potting mix) |
| Temperature | Warmth-loving and frost tender; keep above about 10 °C |
| Propagation | Seed; semi-hardwood cuttings (see notes) |
| Toxicity | Aromatic resinous sap; not known to be seriously toxic, but best kept away from pets and children |
Boswellia nana is a dwarf frankincense tree endemic to the island of Socotra, Yemen, prized by caudiciform collectors as a naturally miniature pachycaul. Even as a mature plant it stays small, forming a squat, swollen trunk and caudex topped by short branches, which makes it one of the most sought-after species in the genus Boswellia for bonsai-style pot culture.
Description
Boswellia nana is a diminutive, deciduous succulent tree. Its trunk is disproportionately thick and bottle-like for the plant's size, tapering into a few stubby, gnarled branches that give even young specimens the look of an aged miniature tree. The bark is smooth and papery, often peeling in thin flakes and ranging from pale grey to coppery tones.
The leaves are small and pinnate, clustered toward the branch tips, with softly toothed or crinkled margins. Like other Socotran frankincenses the species is drought-deciduous, shedding its foliage to sit out the dry season. Small pink flowers are borne in loose clusters, adding to its appeal as a compact ornamental. When wounded the plant exudes an aromatic resin typical of the frankincense family.
Distribution and habitat
The species is endemic to Socotra, a biologically isolated island in the Arabian Sea that is home to a remarkable concentration of unique succulents. There Boswellia nana grows in exposed, rocky situations, frequently clinging to limestone cliffs and crevices where it endures intense sun, heat and long seasonal drought. Its dwarf, caudex-forming habit is an adaptation to these harsh, wind-blown sites and thin soils.
Socotra's endemic Boswellia species face significant conservation pressure from grazing, habitat degradation and a changing climate, and several are considered threatened. As with all wild-collected succulents, plants in cultivation should come from responsibly propagated stock rather than habitat.
Cultivation
Boswellia nana is a warmth-loving plant that rewards patience. Grow it in a very free-draining, mostly mineral mix in a shallow or snug pot that shows off the caudex, and give it the brightest position you can — strong light keeps the trunk fat and the branches short. Water regularly while the plant is in active growth and leaf, then reduce as it begins to drop its leaves and keep it dry during its winter rest. Cold, wet roots are the surest way to lose one, so err on the dry side and keep it above about 10 °C.
As a naturally slow, self-dwarfing species it needs little pruning, though the caudex and branch structure can be gradually shaped over years for a bonsai effect. See Watering and Repotting for general technique.
Propagation
Seed is the most reliable way to obtain plants with a proper swollen base and caudex, and seedlings develop their characteristic form early. Fresh seed sown warm on a gritty, mineral surface gives the best results; see Propagation — seed.
Semi-hardwood cuttings are sometimes used and can strike, but cutting-grown plants often build a less pronounced basal caudex than seed-raised specimens, so seed is generally preferred by collectors who value the swollen base.
Common problems
- Rot — from overwatering, a poorly draining mix, or water sitting on the plant during dormancy; the caudex softens and the plant collapses.
- Leaf drop out of season — usually a natural response to cold, dryness or a check in growth rather than a disease; the plant leafs out again when conditions improve.
- Pests — mealybugs (white fluff in the leaf axils and on roots) and the occasional spider mite are the main nuisances. See Pests and diseases.
See also
- Boswellia — the genus overview
- Frankincense · Caudiciform plants
- Soil and potting mix · Watering · Repotting · Propagation — seed · Propagation — cuttings