2018 ASHS Annual Conference

Herbaceous perennials are propagated in early spring to late fall when outdoor daily temperatures and photosynthetic daily light integrals (DLIs) vary greatly. Inconsistent environmental conditions poses a challenge for propagators to consistently callus, root, and yield compact herbaceous perennial rooted liners. Research objectives were to evaluate and compare the effects of indoor sole-source lighting (SSL) delivered from red (R) and blue (B) light-emitting diodes (LEDs) to greenhouse supplemental lighting (SL) provided by high-pressure sodium (HPS) lamps during herbaceous perennial propagation. Cuttings of perennial sage (Salvia nemorosa L. 'Lyrical Blues') and wand flower (Gaura lindheimeri Engelm. and A. Gray 'Siskiyou Pink') were propagated in a walk-in growth chamber under multilayer SSL provided by LEDs with red [R; (660 nm)]: blue [B; (460 nm)] light ratios (%) of 100:0 (R₁₀₀:B₀), 75:25 (R₇₅:B₂₅), 50:50 (R₅₀:B₅₀), or 0:100 (R₀:B₁₀₀) delivering 60 µmol·m^–2·s^–1 for 16 hours (DLI of 3.4 mol·m^–2·d^–1). In a glass-glazed greenhouse, cuttings were propagated under ambient light and SL provided by HPS lamps delivering 58 µmol·m^–2·s^–1 for 16 hours (DLI of 3.3 mol·m^–2·d^–1). Ten days after sticking wand flower cuttings, callus diameter, a measure of growth, increased regardless of lighting treatments. At 10 d, stem length of perennial sage and wand flower propagated under SSL R₅₀:B₅₀ LEDs were 21 and 30% shorter and accumulated 50 and 8% greater root biomass, respectively, compared to those under SL. Cuttings propagated under SSL R₅₀:B₅₀ LEDs were similar or greater quality than cuttings under SL and thus, indicates that perennial sage and wand flower cuttings can be successfully propagated under LEDs in a multilayer SSL propagation system.