Stockplant Management for Optimized Rhizogenesis in Tectona grandis Stem Cuttings

Abstract

A 5-year stand of teak (Tectona grandis L. f.) was coppiced in 1999 and converted into a vegetative multiplication garden. Subsequently, three harvesting regimes for the collection of single node stem cuttings were imposed: (1) once – in March (H ₁), (2) twice – in March and September (H ₂) and (3) three times in March, July and November (H ₃). Cuttings were treated basally with either:- T ₀ – control (6 h in water), T ₁ – half the recommended dose of a mixture of IBA and thiamine (500 ppm IBA  + 400 ppm thiamine) or T ₂ – the full dose of the same mixture (1000 ppm IBA  + 800 ppm thiamine). Cuttings receiving IBA  + thiamine rooted significantly better than untreated cuttings, but even the best treatment only resulted in 38.3 ± 3.8% rooting. This treatment produced the greatest number of roots (5.2–12.1). The full dose treatment appears to have been supra-optimal. Rooting ability was also affected by the frequency of stockplant pruning, with cuttings from stockplants pruned twice per year having the greatest rooting percentage (27.8 ± 3.8%) and the most roots (9.2 ± 4.8). This bi-annual pruning (H ₂) resulted in the greatest number of rooted propagules (2.6 and 4.2 times more than H ₁ and H ₃, respectively). There was a significant interaction between Treatment × Pruning frequency. Bi-annual hedging of teak stockplants is recommended for practical purposes, although further work is required to achieve commercially acceptable levels of rooting from coppiced tree stumps.