Lighting is the key to healthy houseplants. Without enough lighting, or the right lighting, houseplants won’t thrive.

If you want to make sure that your houseplants have enough light, the best way to do that is checking available light with a plant light meter. A light meter enables you to accurately measure the quantity of light in each room.

You may think that your eyes are pretty good at determining the amount of light in your home, but once you try a light meter, you’re probably going to be surprised. You may find that your estimations are pretty far off, which can explain why you have ailing plants.

Correct light for houseplants vital

Knowing the exact amount of light a room receives helps you make the right decisions in plant placement. While you can use a photographer’s light meter, they are  designed to be sensitive
to the same light wavelengths as the human eye, which is not what a plant “sees.” It’s a good idea to use a plant intensity light meter. Such gadgets measure the wavelengths used for photosynthesis and chlorophyll production.

Light meters usually show foot-candles, which is the amount of light a candle gives off in all directions one-foot from the flame. The light intensity of a sunny summer day is approximately 10,000 foot-candles. Some meters show low, medium, or high, while others show foot-candle measurements.

Tips for using a light meter

1) Measure the light intensity at leaf level.
2) Determine the required light requirements of what you’re growing. (See list below.)
3) Take readings at different times of the day from various locations near the plant and at several distances from the light source.

Required light candle levels for common houseplants

The categories in which each of these plants appear are the lowest light in which they can survive. Many of the plants can be grown in higher light levels.

Low-Light Plants (50 to 100 foot candles)

Arrowhead vine
Cast-iron plant
Chinese evergreen
Dracaenas, various
Peace lily
Pothos
Philodendron
Radiator plant
Sansevieria

Medium-Light Plants (100 to 300 foot-candles)

African violet
Aluminum plant
Anthurium
Coleus
Ctenanthe
Creeping fig
Croton
Dracaenas, various
Dieffenbachia
Ferns, various
Fiddle-leaf fig
Fittonia
Goldfish plant
Grape ivy
Lipstick plant
Palms, various
Peacock plant
Polka-dot plant
Prayer Plant
Purple velvet plant
Rubber tree
Schefflera
Spider plant
Split-leaf philodendron
Wandering Jew

High-Light Plants (300+ foot-candles)

Begonia
Cacti/Succulents
Citrus
Ficus benjamina
Orchids, various
Hoya
Zebra plant

Too Much Light for Houseplants or Not Enough?

Knowing if you have the right amount of lighting for your houseplants starts with taking a close look at the plants. There are definite signs of over or under lighting.

Signs of inadequate light for houseplants

• Stretching and reaching for light
• Sparse growth, with long distances between leaf sets. (Dense growth indicates adequate light.)
• Lower foliage loss (Available light can only sustain top leaves.)
• Overall loss of vitality. Leaves may be pale and flowers may be sparse or nonexistent
• Pest and disease problems

Rectify inadequate houseplant lighting problems by adding full-spectrum lighting to your home.

Signs of too much light for houseplants

• Scorched leaves that are browned or bleached on the window side
• Overall yellowing and thickening of new growth
• Excessively compact and stunted growth
• Foliage curled downward
• Wilting when adequate moisture is present in the soil
• Lighter than normal leaves

Rectify over-lighting conditions by moving plants away from the window or installing adjustable shades, curtains, or blinds.

Have a lighting problem with your plants? Comment here or send an email for some tips.