Preliminary study on in vivo rooting of ornamental shrubs growing in peat-free growing media

Studies on the use of peat-free growing media to grow potted ornamental plants are nowadays increasing, due to environmental concerns around the exploitation of peat, but these kind of studies on materials suitable to replace peat in the medium of cultivation are lacking with respect to cutting production. In this work, we investigated rhizogenesis on cuttings of four ornamental species (Viburnum rhytidophyllum L., Pyracantha koidzumii x P. coccinea 'Mohave', Prunus laurocerasus L., Euonymus japonicus Thunb., Ligustrum sinense Lour.) planted on the following growing media: 1) peat:pumice 70:30 v v-1 (control); 2) coconut coir dust:pumice 70:30 v v-1; 3) coconut coir dust:green compost 55:45 v v-1; 4) coconut coir dust:green compost:stabilized wood fibre 40:30:30 v v-1; 5) coconut coir dust 100 v v-1; 6) green compost 100 v v-1; 7) stabilized wood fibre 100 v v-1. 12 cm-leafed-cuttings (with 4-6 leaves) were prepared and treated with 4000 ppm indole-3-butyric acid (IBA), 4000 ppm 1-naphthaleneacetic acid (NAA), 4000 ppm IBA+NAA or without hormones. After 120 days, rooting and shooting were evaluated taking into account dry weight of roots, the root length and the root area (cm2). Cuttings grown on substrates with green compost and coconut coir dust generally tended to have same performances of cuttings grown on peat-based media while the cuttings grown on stabilized wood fibre media showed lower rooting grown. In general, data showed that green compost and coconut coir dust could represent excellent substitutes and alternatives to peat for the cultivation of cuttings in commercial nursery providing innovation elements regarding the total elimination of peat during the propagation phase of plants.