Plants require light to produce food and energy. Without light they will start to show signs of deficiency and eventually die. However, plants can survive if some provisions are made so that they can receive a source of light.
The length of time a plant can survive without light can be between 4 to 20 day depending on the amount of light the plant is normally subjected to. Low light plants can go from 12 to 20 days, whereas light loving plants can merely last between 4 to 10 days before they die.Without light plants will die from chlorosis.
In this article we will discuss how lights affect plants, what plants can tolerate low light and what you can do to help provide some source of light so that you can prolong the life of your plant whether it’s in shipment or locked in an isolated room.
How light Affects a Plant’s Survival
The amount of time your plant can go without light depends on the type and age of the plant.
For many people, for instance if you are moving from one state to another or you have plants in rooms that are not always lit then this is a very valid question.
Plants can also go into a state of dormancy during low light periods.
For plants, dormancy declares when to prepare their soft tissues for freezing temperatures, dry weather, or water, nutrient and light shortage. Instead of exerting energy in an attempt to grow, they know to stop growing and conserve energy until growing conditions are returned to normal.
The lack of light will affect any plant, whether the plant loves light or not. All plants require a certain amount of light to survive.
However, while there are some plants that can thrive with very little light, for most types of houseplants this will lead to death within a few weeks.
Plants that can survive for long periods without a source of light are normally very green, non flowering plants.
Plants that love light are –
- Jade plant
- Aloe Vera
- Garden Croton
- Umbrella Papyrus
- Tropical Hibiscus
With respect to succulents, they are light loving plants that can tolerate a full 12 hours of sunlight and whenever light is limited for a long period of time, the leaves will start yellowing and begin to shed.
Why do Plants Need Light to Survive?
Plants need light to survive. Plants use the sun for energy to make food. They also need it to produce flowers and grow new leaves. Without enough sunlight, plants will start to die from lack of nutrients and energy- a condition called chlorosis or etiolation.
Chlorosis is a yellowing of leaf tissue due to a lack of chlorophyll. Leaves can also lose their color and become transparent.
Etiolation is a process in flowering plants grown in partial or complete absence of light. It is characterized by long, weak stems; smaller leaves due to longer internodes; and a pale yellow color [Source]
Possible causes of chlorosis include poor drainage, damaged roots, compacted roots, high alkalinity, and nutrient deficiencies in the plant.
How Much Light do Plants Need?
Plants that need to be grown in a windowless environment, example flowering plants and vegetables, will require 12-16 hours of light per day. 8 hours without light is the maximum amount of darkness needed for these types.
As stated before most plant species can’t survive without being able to receive at least some type of natural daylight or artificial lighting.
However there are certain exceptions such as flowers which rely on an 18 hour dark cycle followed by 6 hours or more during their blooming period.
During this period they should only have access to bright lights indoors from 3 PM until dusk when it’s time for them go into another six hour phase again under complete blackness so as not affect the photoperiod too much
Photoperiodism is the physiological reaction of organisms to the length of night or a dark period. It occurs in plants and animals. Photoperiodism can also be defined as the developmental responses of plants to the relative lengths of light and dark periods. [Source]
Some plants are photosensitive and need a certain amount of darkness in order to bloom. These plants are adapted to seasonal changes and are known for blooming within the winter months.
Some examples are
- poinsettias (Euphorbia pulcherrima)
- orchids (Orchidaceae spp.)
- cacti (Cactaceae spp.)
There are plants that can tolerate almost a full 24 hours of light and those are plants that are most comfortable growing indoors where they are also exposed to artificial lights during the night.
Plants that can tolerate a full 24 hours of light are –
- Swiss cheese plant (Monstera deliciosa)
- Dieffenbachia (Dieffenbachia spp.)
- Coleus (Coleus hybridus)
How do Plants React to Low Light?
Plants can react to the light they are given. They will grow towards and away from different sources of light, depending on how much they need.
This means that if you’re not giving your plant enough light–even if it’s just a little bit less than what it needs–it can begin to wither and die.
Low lighting conditions can produce legginess in plants.
Legginess can be caused when a plant is exposed to low light conditions and it searches out the little light that it finds.
What happens is that the plant would produce auxins that would promote growth along the stems of the plant causing it to have an elongated shape.
It’s not directly dangerous for a plant but the long stalk or stem does tend to be weaker than it normally would be.
Plants that are affected by legginess and low light are mostly vinned plants such as
- Monstera deliciosa ( See our detailed article on leggy Monstera and How to fix it)
- Elephant ears
- Ivy Plant
- Arrowhead Plant
Do Plants also Need Darkness?
Periods of darkness are required for plants as it affects their metabolism. Plants use the light from the sun during daylight periods to create and store energy. This stored energy is then metabolised and used to grow during the dark cycle of a plant’s circadian rhythm.
A plant’s circadian rhythm is when a plant synchronizes with the light cycle of its surrounding environment.
This is more pronounced in larger plants as there are more biological reactions occurring within the plant.
More energy stored = more time to metabolize
Plants that will survive well in Low light conditions
There are many plants that will survive in low light conditions. However low light doesn’t mean “no light” and the plant will be able to adapt to whatever lighting conditions that its provided with.
A few examples of plants that can tolerate low light are:
- Chinese evergreen
- Spider plant
- Snake plant
How to Provide Lights for Plants
Light can be provided for plants by simply using an LED grow light. Grow lights are formulated to provide plants with the optimal amount of light within the lighting spectrum.
It was found that plants use a great deal of red and blue light from the spectrum for growth and manufacturers have capitalized on this creating LED grow light that suits the need of plants. With only red and blue light being emitted, the mixture of colors gives the emanating light a purple hue.
However, This theory was debunked and it was shown that plants also use the other parts of the spectrum for their overall development which means that a normal LED light can be used as a temporary light source to ensure that your plant survives.
If you would like to see how artificial light affects plant growth you can check our detailed article on how porch lights affect plants.
Too much light can be dangerous and the lack of rest for plants can lead to weak root growth and fruiting ability. 24-hour grow lights can overwork a plant and diminish long-term health.
Plants can survive long periods without light. However the length of time a plant survives is dependent on the type of plant in question.
Plants like jade plant and succulents are well adapted for full sunlight and cannot tolerate long periods of darkness.
Plants exposed to little light will start to show signs of deficiencies and leggy behavior.
When it comes to growing plants, you’ll want them in the light for 12-16 hours per day.
Flowering plants will need more than that. You should make sure your plant gets 8 straight hours of darkness every night so they can grow properly!