Photoperiod Lighting Information

Photoperiodism is the actual duration or length of the day (photoperiod) and is a significant factor in the growth and flowering of a wide variety of plants. The controlling effect of photoperiod is called photo-periodicity and can be controlled by the addition or reduction of light. Most floriculture crops have one of three flowering responses to photoperiod:

Long Day Plants Short Day Plants Day Neutral Plants

Long day plants are plants that bloom when light duration is more than 12 hrs per day. Day extension can be achieved with low light levels of 10-15 foot candles. Examples: Petunias, carrot, oats and rye. Long days can be manipulated by the addition of light. Short day plants are plants that bloom when light duration is less than 12 hours per day. Examples: Poinsettias, Tobacco, Dahlia and cosmos. Short days are typically produced by removing the light source to the plant. This is typically achieved by blanketing the plants with a “black out” curtain system.

Day neutral plants are plants that show little response to length of day light. Examples: Cucumber, cotton, tomato and potato.