Growing Indoor Plants Under Supplemental Lights

Care and How To

Light is important for plant growth. Without it, there is no photosynthesis, and plants cannot grow and thrive.  Light is often the most limiting growth factor when growing houseplants, starting seeds, or nurturing any plant indoors.

Seedling under supplemental light
Supplemental light is beneficial for starting seeds indoors.

In the home, even the brightest windowsill only has a fraction of the light intensity of any outdoor location. Light levels are particularly low in the winter because of the short days, low angle of the sun, and often overcast weather. While houseplants differ in their lighting requirements, many benefit from supplemental lighting either during the winter or year-round.

Below is a guide to providing supplemental light for houseplants, seedlings, and other indoor plants.


Considerations for Supplemental Light  |  Sources for Supplemental Light  |  Supplemental Light Set-ups  |  More Information


Considerations for Supplemental Light

Three important factors need to be considered when providing light for plants: Quality, Intensity, and Duration.

These three factors are used to determine the light requirement needed for best growth, called the daily light integral (DLI).  This is one of the most important measurements for growing plants under lights. 

Learn more about the important factors that need to be considered and how to calculate the DLI in this article: Important Considerations for Providing Supplemental Light to Indoor Plants.


Sources for Supplemental Light

Light Cart with plants By DimaBerlin AdobeStock_681231680
Many sources can provide supplemental light, including these LED fixtures. Photo by Dima Berlin.

Many different types of fixtures are available to provide light for houseplants, seedlings, or other indoor plants. 

The supplemental light sources available to home gardeners include LED, fluorescent, and others.  Which you select depends on several factors as each light source has advantages and disadvantages.

Factors to consider include light intensity (amount), wavelength emitted, cost to purchase, efficiency, and the amount of heat produced.   

Learn more about selecting the best source of supplemental light for indoor plants in this article: Sources for Supplemental Light for Indoor Plants.  


Supplemental Light Set-ups

Once you've determined how much light your plants need (a target daily light integral or DLI) and what type of fixtures you wish to use (LED, fluorescent, etc.), you can build a supplemental light setup perfectly suited to provide the best light for your indoor plants.

Supplemental Light Stand - metal shelf
Supplemental light setups can be purchased or built to suit your needs.

Information on how to determine the number of fixtures that will be needed, what factors to consider when building your setup, and example setups you can use at home can be found in this article: How to Set Up Supplemental Lights for Indoor Plants.


More Information

Authors: 

Aaron Steil Consumer Horticulture Extension Specialist

Aaron Steil is the consumer horticulture extension specialist at Iowa State University where he works with county Extension offices across the state to answer home gardening questions for all Iowans.  This includes information related to trees, shrubs, vegetables, fruits, herbs, perennials, ...

Last Reviewed: 
December, 2023