Potted greenhouse-forced `Nellie White' Easter lilies (Lilium longiflorum Thunb.) were irrigated from emergence with water at 2, 5, 8, 11, or 15 °C either onto the shoot apex (overhead) or onto the substrate for a 0, 2-, 4-, 6-, 8-, 10-, or 12-week period. Control treatment was at 18 °C, either overhead or on substrate. When irrigation water was applied overhead for the entire period between emergence and flowering (12 weeks), plant height increased linearly with the temperature of irrigation water (1.75 cm/°C). As the period of application with cold water increased from 0 to 12 weeks, plant height decreased both in a linear and a quadratic manner. Forcing time was negatively correlated with height with the shortest plants delayed by 3 to 6 days. Water temperature did not affect bud abortion or the number of yellow leaves. Irrigation water temperature had no effect on plant parameters when applied directly on the substrate.
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