Background: Arachnis annamensis Rolfe is a rare and endemic monopodial orchid in Vietnam, threatened by low seed germination due to obligate mycorrhizal dependence. Vegetative propagation is therefore essential for large-scale multiplication and conservation. 
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Methods: A stem cutting technique was evaluated under nursery conditions using 810 cuttings. Treatments included three cutting types (2, 3 and 4 nodes with aerial roots), three substrates (rice husk + sawdust + soil; rice husk + charcoal + soil; rice husk + soil) and three auxin applications (IBA 1000 ppm, NAA 1000 ppm and control). 
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Result: Cuttings with 3-4 nodes showed higher sprouting rates, faster shoot emergence, greater elongation and stronger rooting than 2-node cuttings. The substrate mixture of rice husk, sawdust and soil (1:1:1, v/v) provided the best aeration-moisture balance, while IBA at 1000 ppm significantly enhanced bud activation and root induction compared with NAA and control. Propagation efficiency strongly relied on the presence of aerial roots, enabling direct bud activation rather than callus-mediated regeneration. This optimized protocol represents a reliable strategy for clonal propagation and ex situ conservation of A. annamensis.

Optimization of Clonal Propagation Protocol for Arachnis annamensis via Stem Cuttings under Controlled Nursery Conditions