Houseplants can be a bit finicky when it comes to getting their ideal light conditions. Nailing the right amount makes all the difference—too little, and they become leggy and weak; too much, and they end up sunburned and dried out.
Most houseplants originally come from tropical regions, which is why they love the warmth of our homes. Some naturally grow under dense rainforest canopies, where light is dim and humidity is high, while others thrive in open spaces with plenty of sunlight. The big question is: how do you mimic these conditions inside your home?
Before bringing any houseplant indoors, Justin Hancock, a horticulturist and plant expert at Costa Farms, suggests doing a quick check to make sure the room suits its needs. “Assess your space before even buying the plant,” he says. “Most houseplants handle average home temperatures just fine, and many do okay with normal humidity (though they’d prefer a bit more). But getting the light right? That’s the real game-changer for keeping them happy.”
To ensure your houseplants get enough light, Justin recommends always doing the Shadow Test before placing a new plant in a room.
What is the Shadow Test?
It’s a simple but effective way to check light levels in your home and see if a spot works for your plant. By observing the shadow cast by an object (or even your hand), you can tell whether the light is bright, medium, or low. “Use this as a guide so you don’t put a high-light plant in a dim corner,” Justin advises.
Keep in mind that light shifts with the seasons—a room with medium light in summer might offer only low light in winter. That’s why it’s smart to test light levels year-round and move plants as needed.
Check Your Plant’s Light Requirements
Houseplants usually come with care tags listing their preferred light conditions. Always check these details. “One thing to remember,” Justin explains, “is that most tags list the minimum light needed for survival. So, many low-light plants can actually handle brighter spots.” Just be careful with more delicate plants, like orchids.
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Many plants love bright, indirect light—meaning a well-lit room but not right in the window. You can also diffuse harsh light with a sheer curtain.
How to Perform the Shadow Test
Some experts say to use your hand at midday, but Justin recommends using an object and checking at different times for the most accurate reading. For best results, do the test on a clear, sunny day.
“Place a solid object where you plan to keep your plant and observe it throughout the day,” Justin says. If the surface is dark or textured, set the object on white paper to see the shadow better.
- Sharp, well-defined shadow? Bright light.
- Softer, less distinct shadow? Medium light.
- Faint or no shadow? Low light.
If you’re short on time, a quick midday check with your hand works too. Hold your hand about a foot (30cm) above a sheet of paper where the plant will go. A crisp shadow means bright light; a fuzzy but clear shadow means medium; a faint, blurry outline means low light.
How to Improve Light Levels for Houseplants
“Since light weakens the farther it travels from the window, moving plants closer can help,” Justin notes. “Grow lights are also a great boost, especially in winter.”
Dusty leaves block light, so wipe them down regularly. “Clearing off dust lets in more light and can even knock off pests,” he adds.
If a room stays dim with no easy fixes, opt for low-light plants. Justin’s top picks: ZZ plant (Zamioculcas zamiifolia varieties), snake plant (Dracaena trifasciata varieties), and Chinese evergreen (Aglaonema varieties).
More Houseplant Inspiration
- Best plant combos for every room, from shady living areas to sunny kitchens.
- My easy homemade orchid fertilizer recipe for more blooms.
- Rare plant expert shares 5 stunning, low-maintenance varieties to upgrade your collection.