The Difference Between Short-Day & Long-Day Plants

Light Duration

• A photoperiod is the duration of light and dark received by a plant within a specific period of time, such as a 24-hour day. Photoperiods change with the season as the sun provides longer periods of daylight in the summer season and increasingly shorter periods of sunlight as fall and winter approach. Although the period of daylight is important in photoperiodism, plant biologists have discovered that short- and long-day plants actually sense the periods of darkness and produce flowers as a result of the length of exposure to darkness.

Different Needs for Light and Dark

• Short-day and long-day plants have different needs for light and dark. As the name implies, flowers begin to form on short-day plants as the period of daylight shortens to less than 12 hours and the night grows longer because they need the longer periods of darkness to bloom. Conversely, long-day plants need daylight exposure of more than 12 hours to produce blooms, followed by a shorter night.

Difference in Blooming Season

• Plants that flower in the fall and winter are known as short-day plants. Once their peak seasons are over, they spend the spring and summer months in a vegetative growth stage that allows the plant to put its energy into the development of new growth and energy storage for the fall and winter months. Long-day plants, on the other hand, bloom during the longer days of the spring and summer months.

Types

• Long-day plants can be observed quickly growing and producing flowers or fruit during the summer months. In your garden you can find examples of long-day plants in the lettuce and radishes you grow. In the wild, clover is an example of a long-day plant. Hollyhocks, irises and purple coneflower are examples of flower-producing long-day plants. Chrysanthemum flowers are a popular fall flower that needs less light, making it a short-day light. Some of the more popular seasonal or holiday flowers, such as poinsettias or Easter cacti, are also short-day plants.