How much light do houseplants need?
Low, medium and bright light, and how to tell what you have
Light is a plant's food
Plants turn light into the energy they live on, and indoors it's usually the thing in shortest supply. Watering and feeding can't make up for too little light, so it's the first thing to get right.
Our eyes are poor judges of light. Full sun outdoors can be a hundred times brighter than a well-lit room, though both look bright to us. A handheld light meter gives the best reading; phone apps are only a rough guide.
Low, medium and bright
Care guides sort plants into rough groups. Light meters measure in foot-candles (fc) or lux; one foot-candle is about 10.8 lux.
- Low light: about 25–100 fc (270–1,100 lux). North windows, or rooms lit by lamps.
- Medium light: about 100–500 fc (1,100–5,400 lux). East or west windows.
- Bright light: about 500–1,000 fc (5,400–10,800 lux). South windows and some west ones.
- Direct sun: over 1,000 fc (10,800 lux), with 4–6 hours of sun, like an unshaded south bay window.
Light fades fast
Light drops quickly as you move away from a window, and curtains, screens, trees and buildings cut it further. Bright, indirect light is strong enough to cast a clear shadow.
Most houseplants, even low-light ones, look their best in bright, indirect light.
Read the plant
Your plant will tell you whether the light is right.
- Too little light: stretched, leggy stems, a lean toward the window, faded leaves, few flowers and lower leaves yellowing and dropping.
- Variegated plants kept in too much shade can turn plain green.
- Too much light: pale, bleached patches that turn brown and brittle, worst when the soil is dry.
Easy fixes
Move a struggling plant closer to a window or to a brighter one, and add a grow light where windows can't do the job. Give plants at least 8 hours of darkness, too.
When moving a plant into strong sun, start with a couple of hours a day and add more gradually. Leaves that grew in shade burn easily.
Related plant problems
Sources
- University of Maryland Extension: Lighting for Indoor Plants
- UF/IFAS Extension: Light for Houseplants
- Iowa State University Extension: Important Considerations for Providing Supplemental Light to Indoor Plants
- RHS: How to help a poorly houseplant
General guidance, not a diagnosis. Written by PlantWiz in our own words from the sources above.