Are White Lights Good for Plants? We Tested It!
White lights are often used as supplemental light for indoor plants. But is it better than natural light? I have devoted an enormous amount of my time to research and experiment on this matter and here are my findings.
Although white light is useful lighting for plants, sunlight exposure is still the best for optimal plant growth. Basil plants grown indoors under white light developed slower compared to plants under sunlight. This is because sunlight supplies more light energy, red and blue wavelengths, needed by plants to make food.
What are the differences between white light and sunlight? What are their similarities? What qualifies white light for its application in plant production? These are questions that will be answered in a while. So let us keep going!
Experiment Materials and Setup
In this experiment, basil plants are used to demonstrate the effect of varying light conditions, namely white light and sunlight. Garden soil was used as a growing medium. The temperature was also monitored and kept at an average of 28°C.
To deliver you the best insight along with tested data, I have conducted a small experiment to test if white light is better than sunlight.
1. Sunlight Setup
Two basil plants were grown separately in different pots using garden soil.
Compare basil with other herbs in our article on basil vs mint.
Each pot in this setup was placed outside, in an area that receives at least 8 hours of sunlight. The temperature under this setup ranged from 27 to 30°C.
2. White Light Setup
Same with those under the sunlight treatment, two basil plants were also sown in garden soil. The setup was located on an indoor shelf with white light positioned 10 inches above the pot. The temperature under this setup ranged from 27 to 29°C.
- Type of light: Light Emitting Diode Bulb in Softbox
- Brand: Philips
- Power: 8.8 W
- Distance of light from the plant: 10 inches above the plant
Experiment Results: White Light vs Sunlight
After a month of experimentation, the basil plants grown under sunlight grew faster and better in terms of plant height, degree of leaf greening, number of leaves, and size of leaves. The basil plants grown under white light were stunted and had small leaves with less pigmentation.
Here are the different processes that occurred in my one-month observation. In a quick glance at the pictures, you can observe that basil plants grown under sunlight performed better.
Week 1: Emergence of Primary Leaves
After the first week of light exposure, the main plant growth that happened in the basil plants is the emergence of the primary leaves. Plants in both setups had primary leaves that were yellow-green in color and measured less than 4 millimeters.
| Factors | White Lights | Sunlight |
|---|---|---|
| Average Plant Height | 0.50 inch | 0.75 inch |
| Leaf Color | Yellow-green | Yellow-green |
| Average Leaf Size | 3 mm | 3.5 mm |
| Average Number of Primary Leaves | 2 | 2 |
| Average Number of Secondary Leaves | 0 | 2 (preparing to grow) |
Week 2: Start of Vegetative Growth
Slow growth was observed for basil plants under white light during week 2. On the other hand, the setup under sunlight continued developing plant structures such as petioles, which are the branch-like structures that hold the leaves, and small leaflets located at the center.
| Factors | White Lights | Sunlight |
|---|---|---|
| Average Plant Height | 0.5 inch | 1 inch |
| Leaf Color | Yellow Green | Green |
| Average Leaf Size | 3 mm | 4 mm |
| Average Number of Primary Leaves | 2 | 2 |
| Average Number of Secondary Leaves | 0 | 2 (increased in size) |
| Other Remarks | None | Noticeable development of v-shaped branch-like structures called petioles. |
Week 3: Development of More Leaves
Under white light, the growth of small basil leaflets has already been initiated by week 3. Whereas, secondary leaves have already begun to develop on plants exposed to sunlight.
| Factors | White Lights | Sunlight |
|---|---|---|
| Average Plant Height | 0.9 inch | 1.50 inch |
| Leaf Color | Yellow Green | Green |
| Average Leaf Size | 4 mm | 5 mm |
| Average Number of Primary Leaves | 2 | 2 |
| Average Number of Secondary Leaves | 2 | 2 |
| Other Remarks | Faster growth is observed | Faster growth is observed |
Note: After this week, the plants were thinned. This means the plants with better performance were left in the pot, while the seedlings with weaker performance were removed. This is a normal thing to do in gardening to have the best set of plants growing in your garden!
Week 4: Leaf Expansion and Height Increase
The basil plants under artificial light experienced slower growth compared to those under natural light. The latter just started to develop its leaflets by week 4. The expansion of leaves under sunlight exposure happened quickly from week 3 to week 4. This can be attributed to the presence of more leaves, thus triggering accelerated growth.
| Factors | White Lights | Sunlight |
|---|---|---|
| Average Plant Height | 1.2 inch | 2.5 inch |
| Leaf Color | Green | Green |
| Average Leaf Size | 4.2 mm | 25 mm |
| Average Number of Primary Leaves | 2 | 2 |
| Average Number of Secondary Leaves | 2 | 3 |
| Other Remarks | None | 2 small leaflets are again visible |
White Light vs Sunlight: Experiment Results
Basil plants grown under sunlight grow better, compared to those grown indoors. In plant production, the usage of white light is permitted in a controlled setup as an alternative to sunlight. However, sunlight still gives the optimum condition necessary for growing most plants.
Since sunlight consists of white light both of them contain necessary wavelengths of light that power photosynthesis, which is the food-making process in plants.
What are wavelengths?
Wavelengths from light are the sources of energy for our plants. They power up the process of photosynthesis and our plants cannot grow their plant parts without light energy. Different bands of wavelength correspond to different colors like red and green. When combined, they all produce a bright white light.
How to Improve Plant Growth Using White Light
Some may argue that white light works best for them, and I can also attest to this. Thus, we need to have a few considerations to explain why your experience may be different from the results of our experiment.
Below are possible reasons why plants may not grow best under white light:
- The light might be too far from the plant. For further experiments or practice, one can distance the white light within the range of 6 to 12 inches away from the seedling, especially if it is already a full-grown plant.
- The white light might be too weak. If you will use white light in a garden with many plants, it is better to use more white lights or those with higher light intensity.
- The light bulb is not designed for growing plants. Although many grow light bulbs produce white light, not all white lights are good alternatives for sunlight.
3 Differences Between White Light and Sunlight
White light and sunlight differ in terms of the light spectrum, heat production, usage, and setup. These are also possible reasons why the plants grown under sunlight performed better than plants under white light.
1. Light Spectrum
Sunlight contains the full spectrum. This means it contains all of the colors of the rainbow along with wavelengths that are invisible to humans, for instance, infrared and ultraviolet. Artificial light sources, on the other hand, imitate white light by supplying only a few colors from the rainbow.
The term ‘all visible wavelengths’ that I used above means white light is the result when you mix red, orange, yellow, green, blue, indigo, and violet lights. Therefore, white light can be used in plant production because it also contains red and blue wavelengths.
Did you know that your plants use red and blue lights to make their own food? Not green, not yellow, not even white!
Because of this, most of the grow lights used in indoor gardens are purple in color. These light-emitting diode (LED) lights are a combination of red and blue wavelengths!
Explore more on this in our article on what is PAR in grow lights?
2. Heat Production
Plants are more exposed to heat when grown under white LED lights because they are in a small enclosed space. As a result, the heat and moisture in the controlled environment is higher especially if without artificial ventilation. Hence, the plant is more prone to experiencing distress compared to its outdoor counterpart.
The heat produced in the indoor setup might also be another cause of the slow growth of basil plants in my experiment. Because of the higher temperature, there could also be heat stress that causes slower development.
Another factor that we could take into account is the height or distance of lights from the plants. Generally, the closer the light from the plant is the higher the possibility of heat stress becomes.
3. Usage & Setup
White lights are used for indoor gardening setups, as they can mimic the light supplied by the sun. They are commonly used for hydroponics, houseplants, and microgreens. On the other hand, sunlight is more appropriate for fruiting vegetables, leafy vegetables, and plantation crops grown in soil.
If you are wondering why sunlight works best with veggies and plantation crops, this is because these types of plants need more energy to produce their harvests.
For instance, since tomatoes undergo a lot of plant development stages, such as the leaf, flower, and fruit development, they will need more energy to power up biological processes.
Explore the quality of market-available grow lights in our article on best grow lights.
Is the Light Used Too Weak?
In this setup, a 8W lamp was used. Despite it might sound very low wattage, such a lamp is more than enough considering that only two small pots growing seedlings were considered.
Indeed, according to this article from the University of Missouri,
- High-light plants like basil, as used in this experiment, need 20 watts per square foot of growing area.
- Most plants should be located with the tips of the plants 6 to 12 inches from the light source.
The setup in this experiment we conducted, the growing area where the two little pots are in is even less than a half square foot, so if we will do the math, an 8-10 watt will be sufficient for growing small seedlings (even more, since they are still seedlings). However, using that light might be too weak if we are growing full-grown plants.
Regarding the distance, I chose to place it farther (10 inches) since the seedlings could experience too much heat (thus stress), and also, the soil will dry easier (due to heat as well, making it hard for water to be absorbed by roots).
White Light vs Sunlight: Which is Better?
Plants under sunlight grow better than those grown indoors using white light. In plant production, the usage of white light is permitted in a controlled setup as an alternative to sunlight. However, sunlight still gives the optimum condition necessary for growing most plants.
Since sunlight consists of white light, they are similar in some properties such as their applicability in growing plants.
Both of them contain necessary wavelengths of light that are crucial for photosynthesis, which is the food-making process in plants.
FAQs
Are white lights better than yellow lights?
White lights are better than yellow lights since it is a combination of all the wavelengths under the visible light spectrum, whereas yellow is just one type of visible light. Thus, in plant production, white light is used more frequently because it also contains the blue and red wavelengths which are needed by plants to power up photosynthesis.
Are LED white lights bad for the eyes?
Extreme, direct, and long-term exposure to white LED lights to the eyes will pose risk in someone’s eyesight. However, in a gardening setup, the amount of white LED used in indoor gardens is completely safe.
Is the white LED light from growing plants different from the white LED house light?
White LED grow lights and regular LED white house lights can both provide the same wavelength and energy to plants during their growth and production. The difference is that white LED grow lights are designed specifically for growing plants, so they come in rectangular and strip shapes to distribute light efficiently.
Summary of Are White Light Good for Plants?
White light is a commonly used light for indoor systems. The experiment conducted in this article investigates the performance of white light as compared to natural sunlight.
After a month of testing, basil plants grown in sunlight emerged quicker and have better quality in terms of plant height, leaf greening, number of leaves, and leaf size. In comparison, basil plants grown in white light were stunted, with yellow-green pigmentation on the leaves and smaller leaves.
Sources
- “Caenorhabditis elegans as a model to study the impact of exposure to light emitting diode (LED) domestic lighting” by Abdel-Rahman, F.H. et al. in Journal of Environmental Science and Health Part A Toxic/Hazardous Substances & Environmental Engineering
- “Lighting Indoor Houseplants” by Trinklein, D.H. in University of Missouri
