Night-Interrupted Lighting Accelerates Flowering of Herbaceous Perennials Under Nursery Conditions in the Southern United States

Abstract

Abstract Night-interrupted lighting (NIL) outdoors in a southern nursery setting was evaluated as a system for accelerated production of herbaceous perennials requiring long days to flower. Treatments were NIL beginning February 1, February 15, March 1, or March 15, and a natural photoperiod control. Compared to plants under the natural photoperiod and depending upon initiation of NIL treatment and year, NIL accelerated and increased flowering of ‘Moonbeam’ coreopsis (Coreopsis verticillata L. ‘Moonbeam’) 7 to 36 days and 20 to 244%, ‘Early Sunrise’ coreopsis (Coreopsis grandiflora Hogg ex Sweet. ‘Early Sunrise’) 3 to 20 days and 26 to 64%, ‘Sunray’ coreopsis (Coreopsis grandiflora Hogg ex Sweet. ‘Sunray’) 6 to 13 days and 21 to 44%, ‘Autumn Joy’ stonecrop (Sedum x ‘Autumn Joy’) 26 to 57 days and 200 to 300%, and ‘Blue Queen’ salvia (Salvia x superba Stapf ‘Blue Queen’) 7 to 12 days and 56 to 83%. Flowering of ‘Red Beauty’ obedient plant (Physostegia virginiana (L.) Benth. ‘Red Beauty) was accelerated 20 to 54 days; however, inflorescence counts decreased 38 to 46% in one year and was not affected by treatments in the second year. Plants of all cultivars, except ‘Autumn Joy’ sedum and ‘Red Beauty’ obedient plant, were taller when exposed to NIL than when grown under the natural photoperiod, however plant quality rating of all cultivars was as high or higher under NIL.