Rapid Propagation and Establishment of Florists’ Hydrangea

Abstract

Abstract Terminal cuttings of Hydrangea macrophylla Ser. ‘Rose Supreme’, ‘Merritt’s Supreme’, and ‘Sister Therese’ were treated with basal dips of 0, 5000, 10,000, or 20,000 mg/kg IBA-talc and allowed to root in 22°C sand under mist for 0, 1, 2, 3, 4, or 5 weeks. Adequate root-system development required 4 weeks for ‘Sister Therese’ treated with 10,000 or 20,000 mg/kg IBA, and 5 weeks for ‘Merritt’s Supreme’ treated with 5000, 10,000, or 20,000 mg/kg IBA. After 5 weeks under mist, no cuttings of ‘Rose Supreme’ had developed an adequate root system. ‘Merritt’s Supreme’ hydrangeas were irradiated continuously with 0 or 84 ± 3 μmol -2s-1, supplemental photosynthetically-active radiation (PAR) supplied by high-pressure sodium vapor lamps, and were grown in an 18°-minimum-temperature greenhouse during the winter months. Plants receiving PAR concomitant with natural daylight developed 7 expanded leaf pairs after 9 weeks, whereas control plants required 12 weeks to reach the same stage. Plants receiving supplemental PAR were significantly taller, yet acquired less leaf and stem dry weight and less leaf area than did plants receiving natural daylight alone.