Investigating the Rooting of Stem Cuttings of Five Mediterranean Salvia spp., as a Means for Their Wider Exploitation in Sustainable Horticulture

Salvia fruticosa, S. officinalis, S. pomifera ssp. pomifera, S. ringens, and S. tomentosa have multiple potential uses in floriculture and the pharmaceutical industry, serving sustainable horticulture and landscaping. The aim was to develop effective asexual propagation protocols for the exploitation of the above species. Thus, the effect of cutting origin, season of cutting collection, and various indole-3-butyric acid (IBA) treatments on rooting stem cuttings was examined. Shoot-tip cuttings were collected either from greenhouse or wild mother plants, in November, February, May, and August and were treated either with Rhizopon dusting powder 0.5% w/w IBA or immersion for 1 min in 0–6000 mg L−1 IBA solution. The cuttings were then placed for rooting in a 1:1 (v/v) peat–perlite substrate, under mist, for 2 weeks and on the greenhouse bench in semi-shade for another 4 weeks. More efficient rooting was succeeded by cuttings, (i) of S. tomentosa, followed by S. fruticosa and S. pomifera ssp. pomifera, while S. officinalis was the most difficult to root, (ii) from greenhouse plants, (iii) collected in autumn or spring, and (iv) treated with Rhizopon dusting powder or 1500 mg L−1 IBA solution. Higher dry weight values of the rooted cuttings were found in autumn. Conclusively, rooting of Salvia spp. cuttings depended on species, mother plants’ physiological state, time of cutting collection, climatic conditions, and auxin application.