Influence of Photoperiod and Minimum Overwintering Temperature on Growth of Nursery Liners

Ten woody plant species were rooted during the summer with half of each species overwintered at 4°C (40°F) and half at 18°C (65°F) minimum night temperature. Half of the plants in each temperature regime received long day conditions while half received short day conditions. By May 1 all species except Snow azalea (Rhododendron obtusum ‘Snow’), Emerald'n Gold euonymus (Euonymus fortunei ‘Emerald 'n Gold’), and deutzia (Deutzia gracilis) had greater dry weights with the 18°C (65°F) long day regime. Deutzia was heavier under the 4°C (40°F) regime with no difference between photoperiod treatments. At 4°C (40°F) only Judd viburnum (Viburnum x juddii) was heavier with the long day regime. Plants grown until June 1, after two flushes of vegetative growth, showed less overwintering treatment effect, but Hetzi holly (Ilex crenata ‘Hetzi’), blue rug juniper (Juniperus horizontalis ‘Wiltoni’), crapemyrtle (Lagerstroemia indica ‘Centennial’), and Judd viburnum (Viburnum x juddii) were larger when grown under the 18°C (65°F) long day regime.