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Keep your houseplants happy by giving them the right type of light.
Madeline Buiano is an editor at MarthaStewart.com, sharing her knowledge on a range of topics—from gardening and cleaning to home.
Published on September 15, 2023 In This Article In This Article
Whether you're an experienced or beginner gardener, few things are more rewarding than watching your houseplants grow. But in order to make that happen, you need to give your plants adequate light, which provides them with energy they need to survive. While all plants need some sort of light source, how much light they require varies from plant to plant—maybe your snake plant can thrive in low light but your monstera needs bright indirect light.
If you're unsure of where in your home to put your houseplants, it's helpful to know the most commonly used terms in relation to houseplant lighting, including direct, indirect, window directions, and beyond.
How much light a specific room in your home gets is typically measured in foot-candles (ftc). A foot-candle is a measure of light intensity, or brightness and is defined as the amount of light received by a 1-square-foot surface that is 1 foot away from a candle. There are light meter apps you can download that will tell you approximately how many foot candles a given area of your home has. For example, if you have a houseplant that needs direct light, you will want to make sure it's place in a spot that receives more than 1,000 foot candles.
Foot-candles: More than 1,000
Direct light is when houseplants get full sun with no obstruction, such as those on a windowsill without a curtain. Knowing which windows in your home receive direct sunlight depends on where in the world you live. In the northern hemisphere, a south-facing window provides hours of sufficient direct sunlight from morning to early afternoon. “A west-facing window is also ideal as this is intense light from the late afternoon to evening hours,” says Adrienne Roethling, garden director for Paul J. Ciener Botanical Garden. Direct sunlight can only be bright (not medium or low) as it means plants require maximum luminescence.
Foot-candles: 100 to 1,000
Indirect sunlight for houseplants is light that has been filtered or is partially shaded. "The sunlight does not directly get to the plant but must pass through a sheer curtain, blinds, or something else that will diffuse the light," says Linda Langelo, horticulture specialist at Colorado State University. You can also achieve indirect light by placing your houseplants far enough from a window’s direct sun. There are three main levels of indirect light:
Foot-candles: 500 to 1000
Bright indirect light means houseplants have access to light but aren’t being hit directly with the sun’s rays. To achieve bright indirect light, it’s best to move the plant about 1 to 2 feet away from the window. An east-facing window is ideal for plants that need bright indirect light, as is a west-facing window (so long as the plant is not in the immediate path of the sun’s hot afternoon rays).
Foot-candles: 100 to 500
Plants that prefer medium light can have either some direct sunlight in the morning or indirect sunlight in the afternoon. "Their preference though is indirect light," says Langelo. "Plants by an east or west window can be set back from the window and do well. North windows with no direct sun are also a good option."
Foot-candles: 25 to 100
Think of low light in terms of walking into a dimly lit room, says Langelo. "Plants that prefer this low light can be in a room with no windows or where the curtains are closed most of the time," she says. If houseplants that prefer low light are catching some rays, however, it should be through a north-facing window.
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While you may understand the difference between each type of light, it can be difficult to know which rooms in your home give you the specific lighting you’re looking for. To make this easier, the following guidelines break down the type of light your plants will receive based on the direction in which a window is facing. (Note that these guidelines are for the northern hemisphere.)
The type of light exposure you receive depends on where you live. "If you live in the northern hemisphere, south-facing windows will receive the brightest light," says Langelo. "If you live in the southern hemisphere, the north-facing windows will receive the brightest light." In addition to the hemisphere you reside in, the seasons can also alter light levels. "In the winter, the intensity of the sun diminishes and in the summer it becomes more intense," she says. So a plant that enjoyed bright light during winter, might need to be moved away from the same window come summer.
There are some instances in which grow lights for houseplants may be necessary. "Consider using grow lights during the wintertime when the daylight hours are shorter," says Langelo. "The LED lights can contribute to your houseplant gaining adequate light. LED provide the wavelengths for photosynthesis to occur." You can also try HID grow lights, which have high intensity and put out a lot of light. "They replicate the sun’s light better than LED or fluorescent," says Langelo. For a budget-friendly option, try incandescent grow lights.
Houseplants that aren't getting enough light will look leggy, meaning the plant will have longer stems with fewer leaves. "The reason for the longer stems is an attempt for the houseplant to reach toward the light source it needs," says Langelo. Additionally, houseplants that don't get enough light may appear yellow. "Leaves that turn yellow and stay yellow may mean the plants need more light," says Roethling. "If the leaves turn yellow than brown or white, then they may be getting too much light."
