Albizia kalkora Seeds | Kalkora Silk Tree
LATIN NAME: Albizia kalkora
COMMON NAME: Kalkora Silk Tree
Plant Profile
Kalkora Silk Tree is a small deciduous tree of the pea family, five to twelve metres tall, with a spreading crown and bipinnate leaves that fold at dusk. The flowers are powderpuff heads of pink-tipped stamens, opening in summer, and the pods that follow are flat and papery.
It grows in China, Taiwan and Vietnam, on warm slopes and at forest edges, and it is the smaller, hardier cousin of the Persian silk tree that fills Mediterranean streets. It tolerates light shade, which is unusual among flowering trees, and it fixes nitrogen through root nodules. The bark is smooth and grey, and on older trees it darkens and roughens at the base.
Science & Biotechnology
Albizia is a pantropical genus of some hundred and fifty species, and the Asian group has been reorganised more than once on molecular evidence. Albizia kalkora is close to A. julibrissin, and the two are sometimes confused in cultivation, though kalkora is usually smaller and has a different pod.
The genus is notable for its nitrogen fixation, which is unusual in the mimosoid legumes, and for the chemistry of its bark, where triterpenoid saponins and flavonoids have been studied for neuroprotective and calming activity. Breeding work has looked at hardiness and at resistance to wilt, which affects the genus in warm, humid climates. Its root nodules form with a wide range of rhizobia, which helps explain why it establishes on poor ground.
Uses & Benefits
The bark is used in Chinese medicine in the same tradition as He Huan Pi, the bark of A. julibrissin, though the pharmacopoeial source is the latter. The wood is light and is used for small items and fuel.
In the garden it is a useful small shade tree, flowering in summer when most trees have finished, and tolerating poor, dry soil through its nitrogen-fixing partnership. It is also planted in reclamation work, where its litter improves the ground beneath it. It also tolerates air pollution, which is why it appears in city planting schemes.
Growing from Seed
The seed coat is hard and waxy, so pour near-boiling water over the seed and leave it to soak for a day, or nick the coat with a file. Sow into a free-draining mix at twenty-two to twenty-six degrees, and expect germination in one to three weeks.
Seedlings grow fast and need staking in their first year. Grow them in full sun, and plant out after the last frost into well-drained soil. The tree flowers best in heat; in cool summers it may sulk. Prune in late winter if the crown needs lifting. Water it through its first two summers, then only in prolonged drought.
Our Take
A smaller, tougher silk tree for a garden that cannot take the full Mediterranean version. Boiling water on the seed is the trick that gets it started. Give it sun and it will do the rest.
Related Reading
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