Definition - What does Light Cycle mean?
The plant light cycle refers to the cycle of light and darkness in which a plant receives. Different durations of light and darkness will affect how plants grow, whether they bloom or not, and other elements. This is an important consideration for indoor and hydroponic gardeners who have little to no access to the natural light cycle.
MaximumYield explains Light Cycle
Plants, like all other living things, have a preferred natural light cycle composed of the durations of light and darkness they need to receive throughout the year.
During the winter, seeds (and evergreen plants) experience long periods of darkness and short periods of light. As winter gives way to spring, the number of hours of light increase, while dark hours decrease. During the summer, plants experience prolonged periods of light, with much shorter periods of darkness. This trend begins to reverse as summer transitions into fall, and fall into winter.
Different periods of light and darkness will affect plants in different ways. Moreover, different types of plants are affected in myriad ways from varying light cycles. For instance, a cycle of 12 hours of light and 12 hours of dark will encourage basil not to flower, but to put its energy into healthy vegetative growth.
In other plant species, 24-hours of continuous light is needed to inhibit flowering, but in others, inhibiting flowering is more directly related to shorter periods of darkness and longer periods of light.
A great deal depends on the time of year when the plant in question naturally flowers. For instance, rosemary flowers in the spring, and generally sets buds in the late fall or early winter. Therefore, discouraging blooming would require lighting conditions that mimic either summertime or wintertime, but not spring.
The light cycle is only one of the factors that affect plant growth, vegetative development, and budding/blooming. Other factors at play include temperature and water. Water stress (a lack of water) can cause plants to bloom prematurely, as can high temperatures. If a plant is susceptible to bolting in hot conditions, then cooler temperatures are needed to prevent blooming. If a plant does not receive sufficient water for growth and development, it will channel what energy it has into reproduction, as the plant sees this situation as an impending drought, and reproduction becomes imperative.