The length of the day and night required for the initiation of flowering is called photoperiod. Depending upon the length of photoperiod, Garner and Allard classified plants into three groups. They are Short day plants, Long day plants and Day neutral plants.
A plant which requires more than 12 hours of day length for the initiation of flowering is called long day plant.
Example of Long Day Plants (LDP)
- Pea (Pisum sativum)
- Sugar beet (Beta vulgaris)
- Cabbage (Brassica)
- Wheat (Triticum aestivaticum)
- Radish (Raphanus sativus)
- Spinach (Spinacea)
- Henbane (Hyoscyamus niger)
The long day plants require nights of less than 12 hours. Hence they are also called short night plants.