Smoke water and smoke-derived karrikinolide, KAR₁, improved germination in some medicinal and aromatic plants

Seed dormancy challenges medicinal and aromatic plant (MAP) cultivation, often requiring lengthy cold stratification or application of germination stimulants such as gibberellic acid (GA₃). We evaluated if karrikinolide (KAR1), smoke water (SW) and food-grade liquid smoke treatments would break dormancy of five MAPs—Alchemilla xanthochlora (yellow-green lady’s mantle), Lavandula angustifolia (true lavender), Rhodiola rosea (golden root), Verbena officinalis (common vervain), and Veronica officinalis (heath speedwell). We hypothesised that KAR1 and SW treatments would break dormancy in species originating in Mediterranean-type ecosystems (lavender, common vervain), offering comparable efficacy to GA₃. KAR1 treatments at 1 μM and 10 μM significantly increased final germination percentage (FGP) in lavender, with cultivar ‘Rapido’ reaching 58.5% and 65.5%, and cultivar ‘Carla’ achieving 34% and 31.5%, compared to GA₃ which produced 67% and 49.5% FGP respectively. In heath speedwell, KAR1 treatments from 0.001 to 10 μM consistently had high FGP (94.5–100%), comparable to GA₃ treatment at 94.5%, indicating near-complete dormancy alleviation. However, only heath speedwell achieved germination speeds similar to GA₃ with KAR1. SW treatments were variable: while Veronica officinalis responded positively at 1:10 and 1:1000 dilutions, Lavandula angustifolia showed no response at these concentrations, and undiluted SW inhibited germination for all species. No detectable response to KAR1 was observed for yellow-green lady’s mantle and golden root. Despite not significantly increasing total germination of common vervain, KAR1 increased germination speed, while SW treatments were less pronounced. While GA₃ was consistently effective in breaking dormancy—except for common vervain—KAR1 and SW treatments are viable alternatives for lavender and heath speedwell. Optimisation of KAR1 concentrations and SW formulations may enhance efficacy. SW could offer a novel, sustainable method, potentially compatible with organic production, for improving germination and thus cultivation of these MAP species.