How many hours of supplemental light do my houseplants need?
Not all houseplants need artificial light, but if yours demonstrate a need for supplemental light in the winter or in a low-light position, there are a few things to keep in mind.
Artificial light is not as strong as natural sunlight. The amount of artificial light needed will depend upon a plant's natural light needs and the amount of light it is getting without an artificial supplement. The type and strength of the artificial light you choose will also impact the number of hours that will be necessary.
For most plants getting some natural light, 12 to 14 hours of artificial light should do but plants can need over 16 hours of supplemental light if there is little natural light. These are estimates and you will need to think about how high your particular plants' light needs are and what is available from natural sources. And remember that all plants need some hours of darkness to remain healthy.
Most flowering houseplants are long-day plants that bloom when the sunlit hours outnumber the hours of darkness. Short-day plants that typically bloom in winter (Christmas cactus, African violet and poinsettia are examples) are exceptions that need short-day photoperiods provided by artificial light to flourish. Give them only about 10 hours of artificial light per day until buds form.
Keep in mind that the efficiency of some bulbs in delivering light decreases as they age, and you may need to adjust exposure to compensate. You should also clean your grow lights twice a month to maintain light efficiency.
Read more about using artificial light for houseplants in our Guide.
Courtesy of NYBG Plant Information Service
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