Optimizing off season chrysanthemum production: influence of covering materials on growth and flowering performance in the low hills of Himachal Pradesh

As a globally important flowering plant possessing significant economic, cultural, and symbolic value, chrysanthemum demands year-round availability. This necessitates a thorough understanding of its photoperiodic regulation. In subtropical low hills (438 m a.s.l., temp. range 29.61–17.69°C), photoperiod manipulation via covering was essential for off season production. This study evaluated the effects of three photoselective coverings i.e. tarpaulin, high-density polyethylene (HDPE), and black satin cloth, on the growth, flowering phenology, and yield of eight chrysanthemum cultivars (four standard and four spray types). The Plants received short days (17:00 to 09:00) via covered tunnels until 60–75% of flower buds per plant exhibited color. Morphometric traits, flowering time, and stem cut yield were assessed under controlled photoperiod conditions. Results demonstrated that covering materials had no significant effect on plant spread, which ranged from 37.34 to 37.90 cm. However, the maximum cut stem weight (24.07 g) was achieved under high-density polyethylene, significantly outperforming the tarpaulin, black satin cloth, and open field conditions. Whereas, the maximum plant height (58.60 cm) was observed under open field conditions. Flowering initiated earliest under high-density polyethylene (HDPE) at 110.47 days, significantly earlier than under black satin cloth (120.63 days). Similarly, the time to harvest was shortest under HDPE (122.72 days), compared to tarpaulin and black satin cloth (131.63 days each). The cultivar ‘White Star’ produced the largest flowers (6.99 cm). Among covering materials, black satin cloth yielded the maximum flower size (5.44 cm), which was statistically similar to that under HDPE (5.31 cm). Cultivar specific responses under HDPE allowed classification into groups based on flowering earliness and productivity. Six cultivars (‘Yellow Star’, ‘White Star’, ‘Purnima’, ‘Surf’, ‘Apricot Parasol’, and ‘Well Spring White’) showed optimal performance for off-season production in the low hills of Himachal Pradesh. These findings highlight HDPE as an effective photoperiod manipulation material, promoting early flowering and higher stem yield, thereby enhancing the potential for commercial off season chrysanthemum cultivation in subtropical mountainous environments.