The mycorrhizal-like fungus Piriformospora indica has demonstrated potential to enhance adventitious root formation (ARF) and increase root weight when applied to the propagation substrate of unrooted cuttings (URCs). Experiments were conducted to determine the effect of P. indica on ARF of six floriculture species: cape daisy (Osteospermum ×hybrida ‘Side Show White’), crossandra (Crossandra infundibuliformis ‘Orange Marmalade’), dahlia (Dahlia ×hybrida ‘Dahlietta Margaret’), lantana (Lantana camara ‘Lucky Yellow’), poinsettia (Euphorbia pulcherrima ‘Champion Fire’, ‘Premium White’, and ‘Supreme Bright Red’), and scaevola (Scaevola aemula ‘Fan Dancer’). The treatments consisted of a peat-based growing medium that contained 5%, 10%, 20%, or 30% perlite colonized with P. indica (volume of colonized perlite/volume of growing medium). Inoculation with 10% to 20% colonized perlite significantly increased the root fresh weight for one cultivar, Supreme Bright Red poinsettia, whereas the 20% colonized perlite treatment resulted in a decrease in root fresh weight of scaevola and cape daisy. Rooting percentage of ‘Champion Fire’ poinsettia and dahlia showed a benefit at specific P. indica treatments, whereas cape daisy displayed a decrease in rooting percentage. Conventional rooting hormone treatment showed beneficial responses for dahlia, and ‘Champion Fire’ poinsettia rooting percentage and a negative response on lantana root fresh weight. This project demonstrates a novel method for delivering a root endophyte to URCs for the purpose of increasing ARF, and the results suggest the potential for P. indica usage for ARF enhancement. However, the results were not consistently beneficial across the eight cultivars tested, so growers would need to conduct in-house trials to identify the best treatments across a range of crop species and cultivars.