As part of our feature series, Plant Parent Basics, in this article you will learn how to distinguish between the different kinds of lights different plants need, and how to provide it for them.
Why is light important to plants?
Light, whether it comes from the sun or grow light, provides warmth and energy for plants to survive. Energy from light is used by plants to make their own food energy.
This ability is known by a common name: photosynthesis. Photosynthesis is a chemical reaction where absorbed energy from light is used to convert carbon dioxide (from the air, thanks humans!) and water (from the soil, thanks roots!) into a sugar called glucose, which is sent back to the roots of the plant and absorbed as food. Oxygen is then released into the air by plants as a by-product of the photosynthetic process. Which is great because that's what we human breathe.
What are the different types of light?
Area with as much light as possible throughout the day, within 2 feet of a south-facing window.
Only a select few of houseplants can tolerate the scorching conditions of full sun. The only species that will flourish in unshaded, continuous sunshine during the summer months (when the sun is at “full blast”) are desert cacti and succulents.
SOME DIRECT SUN
Brightly-lit area, with some sunlight directly falling on the leaves during the day.
This is the ideal light for many flowering and some foliage houseplants, such as corn plants (Dracaena sp.) and snake plants (Sansevieria sp.). Examples of places in your home that are likely to provide this type of light are west-facing windowsills, 2 feet away from south-facing window, or south-facing windowsills that are partly obstructed.
BRIGHT, INDIRECT LIGHT
Area close to but not in the zone lit by direct sunlight.
Most houseplants grow best in this type of light. This area typically extends for about 5 feet around a window which is sunlight for part of the day.
Moderately-lit area, within 5 to 8 feet of a sunlit window or close to a sunless window.
This is the favorite type of light for many foliage houseplants, such as prayer plants (Maranta sp., Calathea sp.) and ferns. Most of the plants in the ‘Bright, Indirect Light’ category can also adapt to these conditions.
Poorly-lit area but bright enough to allow you to read a newspaper during several hours of the day.
There are very few houseplants that will actually flourish in this type of light, however many in the ‘Semi-shade’ category with adapt to these conditions.
What does ‘direct light’ mean? What about ‘indirect light’?
Direct and indirect can be taken literally here: Direct light is any light that directly touches the plant, where indirect light is any light that the plant can “see” but that does not actually touch the plant.
Means that there is nothing between the light source and the plant that is subjected to light.
When the plant is not receiving direct light, but is still illuminated to a certain degree.
When do I need a grow light?
Most likely, you won’t ever need a grow light. However, they are useful for those of us who live in shaded or wooded areas, or windowless rooms.
Grow lights can also be used to supplement the duration and intensity of natural light, especially in winter. Keep in mind, plants need rest just like we do. Be sure to provide them at least a month off from their active growing season by limiting time under a grow light.
How do I know if my plants are getting enough light?
Your plant will tell you if it’s getting too much much light. The warning signs include:
Brown or gray scorch patches
Leaves wilt at midday
Leaves have a “washed-out” appearance
Leaves shrivel and die quickly
How do I know if my plants aren’t getting enough light?
Your plant will tell you if it’s not getting enough light. The warning signs include:
Leaves are smaller and paler than normal
Does not fully bloom, or at all, in flowering species
Lower leaves turn yellow, dry up and fall
Variegated leaves (edged or patterned in a second color, typically white or yellow) turn all green
No growth, or spindly growth with abnormally long spaces between leaves