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| Photo courtesy maximumyield.com |
Photoperiodism: the amount of light and darkness a plant is exposed to.
This is the time of year when we make the transition from more darkness to more light in the Northern Hemisphere (the spring equinox). The spring equinox brings the transition of seasons, as the balance of light shifts to make for longer days, shorter nights, and a shift in photoperiodism for plants.
Photoperiodism causes a biological response to a change in the proportions of light and dark in a 24‐hour daily cycle. Plants use it to measure the seasons and to coordinate seasonal events such as flowering. Photoperiodism is important for plants as the amount of uninterrupted darkness is what determines the formation of flowers on most types of plants!
"Short day" (long night) plant requires a long period of darkness. They form flowers only when day length is less than about 12 hours. Many spring and fall flowering plants are short day plants. Examples are: chrysanthemums, poinsettias, Easter lilies, and some soybeans
"Long day" plants require only a short night to flower. These bloom only when they receive more than 12 hours of light. Many of our summer blooming flowers and garden vegetables are long day plants. Examples include: spinach, radishes, lettuce, and irises.
"Day neutral" plants form flowers regardless of day length. Tomatoes, corn, cucumbers and some strawberries are examples.
For more information about photoperiodism and its effects on plants, check out these links: