Understanding Light for Houseplants - Correct Light for Houseplants

Light for houseplants Houseplants require light to grow and live. Light is one of the major components required for plants to make their own food for growth and energy. The process of making food in plants called photosynthesis only occurs in the presence of light energy. Therefore it is very important to provide houseplants with the correct light amount and intensity to ensure that they are growing and remain healthy. If adequate light is not provided, houseplants will grow slowly, become stunted or even die. Providing the correct lighting for houseplants requires the consideration of two aspects of lighting which control growth; the duration and the intensity of light.

The Duration of Light

The duration of light a plant requires is 12-16 hours for most houseplants to maintain active growth. If there is less light, there is reduced food production which results in poor growth of a plant.

The Intensity of Light

The intensity requirement varies enormously from houseplant to houseplant. Some houseplants prefer a sunny windowsill, others light shade, others can tolerate direct sunshine while others relish direct sunshine. See this guide on how to select houseplants based on light intensity.

Signs of too little light;

Variegated leaves turn all-green
Spindly growth with abnormally wide spaces between leaves
Extremely slow growth or no growth at all
Lower leaves turn yellow, dry up and fall
Leaves are smaller and paler than normal
Poor flower formation or no flowers at all
New shoots grow towards the light source

Signs of too much light;

Leaves have a "washed-out" appearance
Leaves shrivel up and eventually fall off
Leaves wilt at midday; when sun is hottest
Brown or grey scorch patches on leaves

A simple light guide for houseplants

In most houseplant care guides the terms used to describe the light requirements may not be clear. The human eye is a poor instrument for measuring light intensity. This simple guide can help you determine the right spot for your houseplant.

Sunny (direct sunshine)

This is an area with as much light as possible. Such a spot is suitable for houseplants that can withstand scorching conditions like Desert Cacti, Snake Plant, Bougainvillea, Hibiscus, Gerbera Daisy, Jasmine and ZZ Plant among others. These include such areas as;

Within 2 ft of a south-or southwest-facing window.
A sun room.
Sunny windowsill.

Brightly lit with some direct sunshine

This is a brightly-lit area with some sunlight falling on the leaves during the day. This spot is perfect for many flowering houseplants and some sunloving foliage houseplants like Saintpaulia (African Violet), Cordyline terminalis (Ti Plant), Rubber Plants (Ficus elastica), Codiaeum (Crotons) among others.

A West- or East-facing windowsill.
A spot within 2 ft from a south- or southwest-facing window.
A partly obstructed south-facing windowsill.

Bright but sunless

This is an area close to but not in the zone lit by direct sunlight; no sunlight falling on the houseplants. Many houseplants like Monstera deliciosa, Spathiphyllum (Peace Lily), Spider Plant (Chlorophytum comosum), Schefflera actinophylla (Umbrella Tree), Dieffenbachias among others grow best when placed in this area.

5 ft around a window which is sunlight for part of the day.
A large sunless window.
Within 4-5 ft of an East- or West-facing window.
3-5 ft of a South- or Southwest-facing window.

Partially shaded (semi-shaded or low light)

This is a moderately lit area. Few flowering houseplants can flourish here but many foliage houseplants like Marantas, Dracaena marginata, Dracaena fragrans, Baby's Tears (Helxine), Pothos among others will grow happily. Most of the bright but sunless foliage houseplants can adapt to these conditions.

5-8 ft of a sunlight window.
Close to a sunless window.
Directly infront of a North-facing window.

Shaded location

This is a poorly lit area but bright enough to read a newspaper during several hours of the day. Only a few foliage houseplants will flourish with the exception of Aglaonema (Chinese Evergreen), Aspidistra (Cast Iron Plant), Asplenium Fern (Bird's Nest Fern), Heartleaf (Philodendron scandens) among others. Many semi-shade foliage houseplants will adapt to these conditions and will actually thrive. No flowering houseplant can thrive in these conditions.

Adjacent windows shaded by trees.
More than 6 ft away from a south- or southwest-facing window.
Hallways, staircases and corners of rooms.

Guidelines for Lighting

Foliage houseplants require bright light without direct sunlight; most will readily adapt to semi-shade conditions.
Houseplants with variegated leaves require more light than those with all-green leaves.
Flowering houseplants need more brighter light with some direct sunlight.
Succulents and Desert Cacti require the highest light intensity of all the houseplants; they prefer sunny conditions to thrive.
Keep the windows free of dust to maintain a high light intensity; dust reduces light intensity by upto 10%.
White or cream-colored walls and ceilings improve lighting by reflecting light in a poor-lit room. A white background will reduce the tendancy of a houseplant to bend towards the light source.
To prevent lop-sided growth of houseplants, turn the pot every time you water; make a quarter turn each time. Do not turn the pot of a flowering houseplant that is in bud formation.
Avoid moving a houseplant from a shady location to a sunny windowsill suddenly; acclimatize it by moving to a slightly brighter spot each day.
You can suddenly move a foliage houseplant to a shadier spot with no ill-effect. It will survive but will not thrive; move it to the brighter spot for about a week every 1-2 months to allow it to recover.

Note: There are many exceptions to these guidelines. Look up the requirements of your houseplant in the Houseplants A-Z Guide.

Guide to Growing Houseplants