Germination and propagation of Lithospermum canescens (Michx.) Lehm., a difficult-to-grow prairie species

Abstract

Hoary puccoon (Lithospermum canescens (Michx.) Lehm. [Boraginaceae]), a common prairie species in high quality, dry to mesic prairie remnants, has been difficult to propagate in the nursery industry. Here, we explore approaches to identify viable seeds, germinate seeds, and cultivate healthy seedlings using both laboratory and greenhouse techniques. Acquiring viable seeds required locating source populations in which near-equal representations of both flower morphs (pin and thrum flowers) were present for this hetero-stylous species. Viable seeds appear to be restricted by plant resources so that the majority of pollinated flowers abort seed production to ensure viability of a lower number of seeds. Germination results in both laboratory and greenhouse experiments indicate that naturally dehiscent nutlets are most viable, and they are identifiable by the presence of a spur-like structure where the nutlet is attached to its receptacle. Large nutlets when the spur was broken in the cleaning process and small nutlets showed lower germination and no germination, respectively. Scarification did not improve germination despite reports of physical dormancy in other species of Lithospermum. Colonization of roots by arbuscular mycorrhizal fungi (AMF) may be key to the success of this species in cultivation. Plants grown with natural soil or soil plugs collected from L. canescens populations showed greater plant survival, vigor, and AMF root colonization than plants grown in commercial (bagged) or soil-less mixes.