Factors Affecting Vegetative Propagation of Wintersweet (Chimonanthus praecox) by Softwood Cuttings

Wintersweet (Chimonanthus praecox) is one of the most popular winter-blooming species. Effective vegetative propagation is necessary for commercial usage and protection of wintersweet. In the current study, the four factors, namely hormone type (A), hormone concentration (B), soaking duration (C), and medium (D), were assessed using an L-16 (4(4)) orthogonal test design. The hormone types include ABT (A(1)), alpha-naphthalene acetic acid (NAA) (A(2)), indole butyric acid (IBA) (A(3)), and indole-3-acetic acid (IAA) (A(4)); the hormone concentrations include 100 mg.L-1 (B-1), 500 mg.L-1 (B-2), 1000 mg.L-1 (B-3), and 1500 mg.L-1 (B-4); the soaking durations include 5 seconds (C-1), 5 minutes (C-2), 30 minutes (C-3), and 3 hours (C-4); and the mediums include perlite: peat in the ratios 1:0 (D-1), 2:1 (D-2), 1:1 (D-3), and 1:2 (D-4). The results showed that hormone and proper medium could significantly improve the cutting survival, rooting, and sprouting, whereas poor factor combinations, especially high hormone concentrations combined with long soaking durations may be threatened to the cuttings and rooting. In actual experiments, we successfully obtained an excellent rooting percentage (62.22%) of wintersweet from treatment No. 5 (A(2)B(1)C(2)D(3)), which is perlite and peat (1:1) as the medium and soaking the cuttings in 100 mg.L-1 NAA for 5 minutes as the hormone treatment. This combination can already meet the requirements for commercial production. A range analysis showed that the medium and hormone concentration were the most important factors affecting the cutting of wintersweet. An analysis of variance also showed that the medium and hormone concentration can significantly or extremely significantly affect most cutting indicators. Moreover, our results revealed that an orthogonal design method is an effective tool for establishing an improved technique for cutting propagation.