| Long day plants | Short day plants |
| 1. Plants that flower only when they are exposed to light period longer than their critical photoperiod are called long day plants (LDP). | 1. Plants that flower only when they are exposed to light period shorter than the critical photoperiod are called short day plants (SDP). |
| 2. The plants usually flower in summer. | 2. The plants usually flower in winter or late summer. |
| 3. These plants require short night period for flowering. Hence, they are also known as short night plants. | 3. These plants require long night period for flowering. Hence, they are also known as long night plants. |
| 4. Plants such as Pea, Radish, Sugar, Beet, Cabbage, Spinach, Wheat, poppy are LD | 4. Plants such as Dahlia, Aster, Tobacco, Chrysanthemum, Soybean (Glycine max) Cocklebur (Xanthium) are SDP |
