All living things need food and water. For plants, sunlight is food. They require light for a process called photosynthesis.
The amount of sunlight needed varies for each plant. Every plant has different light requirements. Incorrect lightening is the second biggest cause of plant demise.
Some plants require more direct sunlight while some don’t require direct sunlight and can do with indirect sunlight or filtered sunlight. There are some plants which thrive in dense tropical jungles which do not like sunlight. These can be grown in our apartments with ease with the help of artificial lights.
All plants can survive for short periods without sunlight. As you know they go through the night where there is no sunlight for a particular duration, but all plants can cope with longer darkness in an emergency.
There are also some plants which have lost the power of photosynthesis altogether. Such plants have no chlorophyll and get all their nutrients by parasitically attaching to the roots of nearby plants instead. Example-broomrape.
Some other parasitic plants called mycoheterotrophic, feed on fungi. They can survive in complete darkness for months or even years. They get their energy by digesting dead plants. Example- coral root orchids.
No indoor plant except for this one can grow in complete darkness. They need some amount of light. Artificial light supplements are ideal in places where there is no sunlight.
Before growing them, however, one should know the natural habitat of the plant and give it the required amount of light.
How to Plants Use Sunlight
As you are aware, plants absorb carbon dioxide from the air through tiny holes in their leaves, branches, stems, and flowers. It absorbs water from the soil through its roots and light energy from sunlight. Now, this light energy triggers a chemical reaction breaking down carbon dioxide and water molecules.
This rearranges them to create sugar (glucose) and oxygen gas. Sugar is then broken down by chloroplasts into energy to fuel the plant’s growth. The oxygen gas produced by the plant goes back into the atmosphere via the same little holes that had absorbed carbon dioxide.
Plants are the only organisms which are able to use the energy from light to produce sugar, starches and other substances needed by them to grow and flower.
If the plant does not get enough sunlight from the sun, the photosynthetic process slows down, even with sufficient carbon dioxide and water. Increasing the light intensity will boost the speed of photosynthesis and thereby boost plant growth.
Let us look into the characteristics of sunlight and their association with plants
The Quality of sunlight matters
Sunlight is energy that comes in varying wavelengths, each with a corresponding color.
Certain wavelengths of light are more important for plant growth than others. The red and blue wavelengths of the light spectrum are the most important energy sources for the plants. They use the colors yellow, red, blue and violet as well as some UV light and infrared light.
Red light encourages budding and blue light promotes foliage growth. Plants appear green because they reflect green light. So the color green is useless to the plants.
Plants growing outdoors or close to the windows are exposed to a balance of wavelengths of light from the sun, including the red and blue lights that plants need.
Intensity/Quantity of Sunlight Matters
Quantity of sunlight is based on the intensity or brightness of light that reaches the leaves. The leaves are after all where the hardworking chloroplasts cells are present in large numbers.
The more light photons that hit the leaves, the more energy captured and the faster the growth. Certain plants like begonias, for example, depend on intense light to sustain their fast-paced growth. Any plant that produces flowers or fruits depends on intense light.
Certain plants have self-regulating mechanisms and will refuse to flower or try to flower and stop midway if there is not enough intense light.
Know that the darkest shade outdoors is still brighter than the sunniest window indoors.
This is because outdoors, the light is bouncing from all angles. From 360 degrees around and from 180-degree arc above in the sky. When a plant is indoors, light usually comes only from one source, like a sunny window. This massively reduces the angles light is bouncing off from, thereby reducing the amount of light and vital photons a plant needs.
When we bring a plant indoors, we literally invoke something called an exponential reduction in photon exposure.
Understanding the light requirements of Indoor plants
Nature has made different plants grow in their unique environmental conditions and that is the beauty of ecology.
You may have heard the terms “ bright light” and “ low light” plants. Let us learn what they mean.
“Bright light” or “ full sun” means there is no barrier either in the form of curtains, blinds, trees or buildings in between the plant and the light source ( a sunny window).
“Medium light” or “filtered sunlight” is sunlight that has been diffused ( sheer curtains) between the plant and the light source ( a sunny window). Some refer to it as “dappled sunlight”. In simpler words, anything partially obstructing the path between the plant and the light source creates this medium light.
“Low light” means no direct sunlight will reach your plant. It is ideal for those plants who live deep inside a jungle or dense tropical forests where sunlight gets blocked by leaves and trees. Such plants require less energy and less food. They are also called “shade-loving” plants.
Getting Sunlight Effect For Indoors Plants
Consider the light options in your homes when purchasing and placing your plant. We just have to mimic the climate of the natural habitat of the plant. This convinces them that they are living in an ideal environment and they thrive.
Aloe, succulents and palm trees are sun-worshipping plants. They should get direct sunlight for at least six hours a day. You need to put such plants in the brightest spot in the room.
Keep plants requiring direct sunlight in balcony or patio or in a south or south-west facing window no more than 6-10 inches from the tip of the plants.
This is where your plant will receive the most bright or direct light while indoors. The intensity drops as the distance increases. Check these plants frequently for watering needs as they tend to dry out faster than other indoor plants.
Ferns and those plants who have evolved to live on the forest floor, they are used to being shaded from the sun. they are not evolved to handle the harsh rays of direct sunlight. This is why medium or moderate light conditions are ideal for them.
Moderate sunlight can be achieved by the east or west-facing window. The further you move away from the windows, less light will be available to the plants. A couple of fluorescent bulbs is also sufficient for this plant when placed away from windows.
Minimum sunlight or low light plants should be placed in the north window. They can be placed in corners of homes as well. They will grow well in artificial light. These plants do not dry out quickly and it is important to check the soil before watering.
The correct amount of sunlight should be provided according to the natural habitat of each plant. Excess of sunlight leads to plants withering down, becoming limp, scorched or burnt leaves.
Too little sunlight, on the other hand, leads to plants becoming pale and thin, dropping of leaves, spaces between leaf nodes become big and they tend to lean towards the light. Flowering plants fail to produce buds.
Important Tips for Indoor/House Plants
- One important thing to remember is that the sun also changes position in the sky depending on the time of day and season. This, in turn, affects how much sunlight your plant will get.
- Keep an eye and monitor the sunlight changes during the day and in different seasons and adjust your plant position accordingly.
- If you keep your plants a few feet away from a window, even a sunny window, your plant is surviving in low light.
If you wish to know how much sunlight your plant is getting, do a shadow test. Take a sheet of paper and hold it up to a light source when the sun is high up around midday.
Take your free hand and place it a foot or so above your piece of paper. A sharp shadow indicates bright light while a softer shadow indicates medium light.
Nowadays there are supplemental lights systems for those who wish to grow plants indoors to make up for lack of natural sunlight. Some of the examples being fluorescent tube lights, LED grow lights, etc.
Remember light is food for the plants. So make sure you understand how much natural sunlight your plants need. Also, understand the light options in your homes and then make your plant selection.
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