Symplocos tetragona Chen Ex Y.F. Wu and Its Cutting Propagation

Tetragonal sweetleaf (Symplocos tetragona Chen ex Y.F. Wu) is a new woody ornamental plant. Since it was discovered in 1996, this small evergreen tree attracted gardeners by its dense, gloss dark green foliage and pyramidal habit. The plant could be distinguished from other species by its yellowish green, tetragonal branchlets. Its fragrant white flowers usually bloom from March to December. The plant grows well from full sun to shade and tolerates various soil types. No injure was observed under -12C (Zone 7).  To promote this new plant for the commercial uses, stem cuttings were collected on 7 August 2008 and treated with IBA and NAA at the concentrations of 1,000, 3,000, and 8,000 mg·L^-1. All cuttings were inserted into 32-cell flats with perlit:peatmoss mix (3:1 by volume) and placed under a mist system. Rooting rate (%) and total root-ball volume were measured 18 weeks later. Rooting hormones significantly increased the root percentage from 40% (control) to 61 to100%. Hormodin rooting powder yielded the highest rooting rates from 87 to 100%, regardless of its concentrations. Higher concentrations (3K and 8K) of K-IBA also produced commercially acceptable rooting rates of 87 and 73%. Double dips with KIBA+Hormodin and KNAA+Hormodin did not show any advantage. Hormodin rooting powder also greatly improved the root quality, which indicated by the total rootball volume. The highest rootball volume, 315.1 cm³, was obtained under the treatment of Hormodin #1. Cuttings treated with Hormodin #2 produced the second highest rootball volume of 268.0 cm³. Both cuttings treated with the lower K-IBA and K-NAA also showed the nice root system of 206.6 cm³ or higher. Stem cuttings of tetragonal sweetleaf could be produced commercially with 1,000 and 3,000 mg·L^-1 Hormodin rooting powder. Donglin Zhang is also a guest professor at the Central South University of Forestry and Technology.