If you ask what grow lights give us, others would say light, and I would say control.
The prime benefit of using a grow light over sunlight is the ability to control the light intensity, spectrum composition, and photoperiod. Although sunlight is free, you have to live with whatever you get.
Sometimes, grow lights are inevitable. Countries near the equator line get ample sunlight, but it’s not the case as we move towards the polars. Also, if you live in a city like Singapore and there’s little agricultural space, you need to grow vertically, and you need to grow lights for it. And if you’re a hobbyist growing in your balcony or garage with limited sunlight, you need them anyway.
But here’s a thing: grow lights may still be a good option even if you have good sunlight.
Everything about the grow light vs sunlight
Before determining which light source is better for your plants, let’s compare the differences between the two in detail. As I already mentioned, sunlight provides everything for the plant. But grow lights give us control, and these features allow us to do so.
Related: how far should grow lights be from plants?
Photoperiod—the light duration
If you live near the equator line, you will get sunlight for about 12 hours a day throughout the year. Moving towards the poles, you experience different daylight during different seasons. Both aren’t the best for plants.
Plants don’t grow well under shorter photoperiods. However, prolonged exposure to intense light can cause light stress in some plants. The optimal photoperiod differs from plant to plant.
What if your plant needs very little light, but you get 12 hours of direct sunlight? You need to block the sunlight after a certain period of exposure. In the same way, what if your plant needs excess light, but you get sunlight only for 4 hours?
Related: How Much Light Does Basil Need?
Related: Low light hydroponic plants
Grow lights offer complete control over this. You can set the light to turn on and off whenever you like. High-end grow lights even offer timers and wi-fi connectivity.
Grow lights are better than sunlight for controlling light duration.
Light intensity
Light intensity is the number of photons the plant receives in a set period. To be more precise, photosynthetic photon flux density (PPFD) is the number of photons received in a square meter area every second.
The challenge is that different plants need PPFDs at different levels. Moreover, the same plant still needs different levels of PPFD at different growth stages. For instance,
- Seedlings grow well in the PPFD range of 100-300 µmol/m²/s.
- During the vegetative stages, 300-600 µmol/m²/s would be the best PPFD for plants.
- Most plants need about 600-900 µmol/m²/s PPFD at times of flowering.
Related: Why Do You Need Grow Lights (Not Regular Lights)
If you grow under the sun, you can reduce the intensity using shade nets. Increasing the light intensity is more challenging, though. You can slightly improve the intensity if you grow in a polytunnel.
Grow lights offer better control over intensity. You can adjust it in a couple of ways. One is to use the grow light’s dimming feature. Most grow lights on the market today are dimmable. If not, try increasing the growth light to reduce the intensity. Since grow lights now are very efficient and produce ample light, you almost always don’t have to worry about further increasing the intensity. If you still want, you can grow inside a grow tent or use reflective materials.
One drawback of grow lights, especially budget ones, is that the intensity isn’t evenly distributed. The PPFD in the center is often higher than the PPFD near the edges. So, if you don’t adjust the lights properly, you may not grow some of your plants or burn the ones in the center.
Light intensity control in grow lights are far more easier than sunlight, though sometimes it can be uneven.
Customizable spectrum
Sunlight, or white light, is comprised of all colors. This means you don’t have to worry about not having a specific band for plant growth. But think again: a plant’s and its grower’s objectives aren’t always the same.
Take lettuce, for example. It wants to grow well, flower early, produce as many seeds as possible, and continue with the next generation. But once the seeds yield, they don’t taste good. We don’t want that to happen unless we intend to produce seeds.
The red range of the spectrum is known to induce reproductive actions in plants, such as flowering and fruiting. You cannot filter the red light in direct sunlight, but you can customize the color spectrum of the red light. Many grow lights are designed to provide more blue light than sunlight to make plants more vegetative.
Grow lights work the other way around for flowering plants. To induce flowering, grow light can produce more red than blue. Similarly, plants use very little of the yellow range, and grow lights can intentionally use less of this range.
Grow light can intentionally produce more blue light for vegetation and red for flowering.
Heat management
Plants have their preferences. Just like humans prefer to be around 75°F, plants have theirs too. For instance, lettuce’s best germination temperature is 70 to 75°F.
But this range isn’t always normal in certain parts of the world. You either live in a hotter or colder climate than you need.
Under the sun, you have little influence over the temperature. You can use coolers, fans, and even HVAC in a greenhouse to reduce the temperature. But battling the dominant sun and the passing clouds is complicated.
Grow lights bring the sun inside. The temperature can be handled more efficiently with just basic ventilation.
Grow lights help us maintain temperature more easily than the open sun
Cost
This is the easiest. Of course, sunlight is free for everyone. Grow light isn’t.
If you still want to investigate this further, you can justify the cost of grow lights. Considering the factors discussed earlier, sunlight may not always be the most cost-effective method for growing plants.
But grow lights cost anywhere between $10 to hundreds of dollars. But people think they are worth the money because of the hidden costs of sunlight.
Sunlight is free, and grow lights aren’t.
When to favor sunlight over grow light.
For most farmers, this sunlight is their natural choice. I think that’s fair.
Even though grow light offers excellent controllability, it’s still an additional complexity. Commercial farming is already complex enough.
Here are the instances where you should prefer sunlight over grow light.
Growing multiple crops
Grow light is customizable, of course. But sunlight has everything. Which means everything the grow lights have and more. For this reason, growling under sunlight works well if you grow more than one variety of plants.
For instance, you have cilantro as a tomato companion plant. The intense red range in the grow light will make cilantro yield, which will not taste good when it yields.
Here’s another example: basil and lettuce grow together. Lettuce produces better results at 11.5µmol/m²/s, which is insufficient for basil. You need to increase the intensity.
Different plant varieties often will have conflicting interests in light. They manage to survive under sunlight. But under grow light, survival is too difficult for them.
Large-field crops
Think of corn, paddy, or wheat. Well, technically, you can grow them under grow light. But how much of the market demand can you satisfy? These field crops are grown on hundreds of hectares of farmland. Covering them with grow lights is impossible. First, you’re going to need an incredible amount of initial investments. Secondly, you’re going to need electricity at an astronomical level.
Big sized crops
Imagine growing coconuts under a grow light. This is, of course, possible. But you don’t want to do it because of maintenance challenges.
Regional crops
Certain crops may have come in the same area you farm. If this is your case, you don’t need to grow lights. That’s because they have evolved to the environment, which is hard for you to create artificially.
Low-value crops
Certain crops in your region may have feeble market demand but excess supply. You shouldn’t grow them with grow lights. You may have to wait much longer to recover the cost of growing light, and if we consider the electricity cost, it may even be unprofitable.
When to grow with grow lights.
Technically, you can grow anything with grow light. Practically, you can’t. But not in these instances.
Crops with a premium value.
Here’s an example—Saffron.
Saffron is the world’s most expensive spice. This is because it’s tough to care for in commercial cultivation. Besides, the yield is very minuscule. Yet, since the demand for saffron is incredible, farmers get a bounty for their harvest.
But modern entrepreneurs use grow lights to grow saffron in shipping containers.
Related: 100W LED grow lights and plants
Off seasonal crops
Traditionally, seasons played a significant role in cultivation. However, with a controlled environment, off-season farming has increased. If you need extra light to grow crops that need ample light, you can use grow lights for them.
When sunlight is scarce or out of control
If you live far from the equatorial line, catching the light to grow anything may be difficult. Regional crops may have evolved to survive the low light. But in every other case, you almost need a grow light.
In the same way, if you want to grow crops that need little sunlight but get too much of them, grow light can help.
Indoor and Vertical farms
Well, you can not build a vertical farm without the help of grow lights. In places where agricultural land scarce, vertical farm offer a promising solution. But when you stack up growing area one over the other, only the top most will get sunlight. Thus most vertical farms are also indoor farms. And they all use grow lights.
In general, you need grow light for all kinds of indoor farming. This includes your balcony which receives partial sunlight and needs a supplemental grow light. This also includes a tiny stack of NFT in your basement where no sunlight penetrates.
When the benefits of grow light outgrow sunlight
Lastly, you can use a grow light whenever you think the benefits of using a grow light is far higher than traditional farming. If you use a grow light, you will have to spend for a few things predominantly.
- The cost of the grow light,
- The electricity cost for running the grow light.
- The electricity cost to cool the grow lights—often comes as part of the grow light in popular brands.
- Grow light maintenance cost.
Take an estimate of these costs for the next 5 years. Now compute the extra yield you’d expect in this period. If the additional yield is sufficiently larger than the costs, you’d better get a grow light.
Related: Grow Light—Plant Count Calculator
In conclusion
Grow lights can be beneficial for crops even if sunlight is abundant. You can customize the spectrum to get a specific outcome from the plant and manually control the photoperiod and intensity. However, all these are not possible or highly challenging if you grow under sunlight.
This is not to say that sunlight is not suitable for farming. Sunlight has been, and will continue to be, the best source of light for plants. They are the best for a variety of reasons. But for specific crops in specific instances, grow light scores well.
