Grow Lights vs Sunlight: Which Is Better?

While we all know that plants need light to thrive, do we know which is better between grow lights vs sunlight? One is a four-billion-year-old nuclear-powered ball of gas a million times larger than Earth and heated to around 27 million degrees Fahrenheit. While the other is a lamp. Which still gets hot, but isn't going to vaporise you. So that's nice.

But when it comes to which one is going to be better for growing and looking after your plants, the differences may not be as obvious as they first appear. In this guide, we'll let you know the key differences, benefits and drawbacks of each, and when each might be most appropriate for your plants.

Grow Lights vs Sunlight: Which Is Better?

Before we get into the details, it's worth briefly running through the way that plants and light interact. We'll try to avoid turning this into a biology lesson. But understanding why light is essential for plants, will help to appreciate the key differences between sunlight and grow lights.

Grow Lights vs Sunlight: Why Plants Need Light

We've probably all heard of photosynthesis, right? This is the way that plants use sunlight to create energy, that enables them to grow and flourish. The chlorophyll in the plant (the stuff that makes plants green) absorbs the light, and converts it into sugars that the plant then feeds on.

More specifically, plants need light from both the red part of the spectrum, and also the blue part of the spectrum. The red spectrum light generally helps with flower buds, while the blue light helps with growing more foliage.

Why are we telling you this? Well, a typical fluorescent lightbulb in your house will provide light from the blue part of the spectrum, while an incandescent bulb tends more towards the red part of the spectrum. The sun obviously offers both. And plants have evolved over millions of years to make the most of the light provided by the sun.

Grow lights are much more sophisticated than simply putting your plant close to a desk lamp. These now come with bulbs that emit light from the full spectrum, much more effectively mimicking natural sunlight. But if all we're doing is mimicking what is already freely available, why bother? It's a good question. Let's look at the benefits and drawbacks of grow lights and sunlight.

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Sunlight Pros And Cons

We'll start with light from the sun. After all, it's much bigger and older than we are. It is also one of the main reasons that Earth can sustain life of any kind. So it's probably deserving of a little respect. Let's start with the benefits of sunlight:

It's free. Sunlight is a virtually limitless resource. It's certainly not going to run out for at least a few billion years. And all you need to do to access it is put your plant close to a window, or outside.

Sunlight also offers all the different wavelengths of light that plants need to grow. This makes sense, as plants evolved to use sunlight as their only source of light. As far as we know anyway. No one has discovered any plant species in the wild that grow or build their own grow lamps. Yet.

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While all this is great, relying on sunlight can have some drawbacks as well:

First of all, sunlight isn't always available as and when you need it. This is especially true in more extreme latitudes, and in the Winter. In Tromsø, Norway, for example, the sun doesn't rise at all between November and January. While from May to July, the sun never sets. While this is an extreme example, if you've bought yourself an exotic houseplant, the natural light conditions available where you live may not be ideal.

Even if you do put your plants close to a window, the strength of the light can be filtered by the glass, reducing its efficacy. And windows can also distort the temperature that a plant is exposed to. In hot weather, some plants may become distressed, or get scorched. And in the cold, plants can easily be damaged by touching a frosty pane of glass, or a draft coming through the window.

Grow Lights Pros And Cons

Luckily, grow lights can mitigate many of the problems of relying on natural sunlight. Let's take a look at the key benefits:

First off, a grow light can be set to provide stable and consistent light conditions no matter the time of year. This means that you can ensure your plants are getting the right amount of light, no matter the season. You can also increase or reduce the amount of light the plant is getting, to ensure each plant gets just the right amount of light. You can't switch off the sun, or tailor its strength to suit your plant.

Grow lights also mean you have more flexibility over where to put your plants. If you have a plant that struggles in shady spots, a grow light suddenly opens up more options for you.

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So does that mean you can draw all the curtains, or live in a bunker, and your plants will still flourish? Well, grow lights also have their weaknesses:

The most obvious disadvantage of a grow light is that because you need to plug it in, it's going to cost you money. Sunlight won't cost you a bean in comparison. There are also costs for the equipment and any replacement bulbs you may need.

And sunlight is, as we said earlier, the perfect light for plants to grow in. It's what they've known for billions of years, so they've evolved to use it. While a grow light can be great, it is always going to struggle to compete with a giant ball of impossibly-hot gas that has fuelled life on this planet since the dawn of time. That's a tough sell.

It's also worth remembering that plants are naturally conditioned to expect cycles of light and darkness. Too much light can actually be bad for a plant, as they do need some darkness in order to thrive.

With all of this in mind, how do you know which one is going to be most suitable for you? We have some thoughts...

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Grow Lights vs Sunlight: How To Decide

There are plenty of factors that may decide whether sunlight or a grow light will be more suitable for you. First, think about how much light your plants are going to need, and consider whether that's something that you can achieve by sunlight.

Many plants need somewhere in the region of 12-18 hours of sunlight every day. Is this achievable where you live? Is your house particular dark, and lacking in sunlight? If so, then a grow light may help you to overcome an absence of natural light.

Do your plants need a consistent, well-regulated temperature? If so, then a grow light may make this easier to provide. The sun, as we know, is impossible to regulate, and plants that get too hot or too cold can suffer.

What type of plants are you trying to grow? Are they native to where you live? If so, they'll be more likely to cope with the natural variations in light levels and temperature that occur as the seasons change. But if you're trying to grow something that has adapted to a very different environment, then sunlight where you live may not help your plant to thrive.

How strong does the light need to be for your plant? The sun is extremely powerful, and grow lights can struggle to match its intensity. They'll consume more energy if you need to crank up the intensity of the light.

Another factor we haven't really talked about is the environmental impact. The sun provides free clean energy. A grow light will cost you money, and will almost certainly leave a carbon footprint. While perhaps less of a factor, it's still important to consider the financial and environmental cost of using artificial light.

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Grow Lights vs Sunlight: Which Is Better?

Hopefully, by now you have a better understanding of the respective merits of grow lights vs sunlight. And when it comes to answering the question of which is better, the answer is a resounding "it depends".

As is so often the case, a wide range of factors will influence just how suitable one choice will be over the other. And in fact, you may find that using a combination of sunlight and grow lights will give your plants the absolute best chance of thriving. The most important thing is that plants are exposed to enough light, whether that's natural sunlight, or via a grow lamp.

Sunlight is of course, what plants have always used. We know it's great. But grow lights are an effective way to supplement sunlight, especially in environments that may be sub-optimal for growing plants.