How to use grow lights for seedlings

How to Use Grow Lights for Seedlings – Best Tips in 2022

We all love to grow our plants from seeds and see them develop into their final, beautiful form, but how much light should seedlings get is always the question.

Sure, growing seedlings in your garden where there is natural light are always good, but for indoor gardeners, that’s simply not possible. And since placing the planted seedlings near a window won’t cut it, using grow lights is the best option.

So let’s see how to use grow lights for seedlings.

Why You Need a Grow Light for Seedlings

Why You Need a Grow Light for Seedlings

Every plant needs oxygen, water, and light to grow and even though providing your plants with lots of oxygen and proper watering isn’t that hard if you’re growing indoors, giving them proper lighting can be tricky.

Placing your seedlings near a window might sound like a good idea, but the window will actually bounce back a lot of the sun’s rays, and could also make your seedlings get more warmth than they need so it’s not the best way to go about getting proper indoor lighting.

So here are some reasons why you need a grow light for seedlings.

1. Germination

When the plant starts to sprout from the seedling the process is called germination and it’s the first step in the plant’s life cycle as it is slowly starting to develop its final shape.

Germination is also the most crucial part of a plant’s development as it is most vulnerable in this stage.

So even though you see your plant starting to sprout, it can quickly stop if it isn’t cared for properly, especially indoors where the environment must be set so that it can match natural conditions.

Grow lights are perfect for germination as you can control the amount of light, and even the type of light you’re using while your plant is going through the process of germination.

2. Weather Conditions

Of course, it’s always a bad idea to plant your seedlings during the winter because different plants grow in different seasons and there’s nothing worse than getting some sprouting and then stopping it because of the cold weather.

However, with grow lights that’s a whole different story as they provide light and warmth to your plant so you can even start growing your plants in the winter.

Also, rainy and cloudy days won’t provide the much-needed amount of sunlight for your plants, but by having a grow light, your seeds won’t have to miss a day of light.

3. Better Growth

Because you can control everything about the light you’re using for growing seedlings, you can stimulate faster and healthier growth by using the specific color of light for your grow lights.

Also, because grow lights have plenty of brightness, your seedlings will grow stockier and healthier, but you’ll also avoid your seedlings from becoming leggy and thin as it sometimes happens when you leave them near a window.

Choosing the Right Grow Light

Choosing the Right Grow Light

Like with any other gardening product, getting a good grow light is crucial for your indoor garden as they aren’t a cheap investment and also we all love our plants so much that we always want to get the best for them.

That being said, there are several things you need to keep an eye out for when choosing a grow light.

1. Light Type

Choosing the right grow lights can be a bit tricky because there are several types of grow lights on the market and they all serve the purpose of providing your plant with the right amount of light.

The most popular choice of course are LED grow lights as they are the brightest and come in various different colors, shapes, and sizes.

Not only that but LED lights are also easy to install and are energy-efficient which is another reason why gardeners prefer them over the other light sources.

Fluorescent lights are also commonly used by gardeners even for seedlings as they provide UV lights which plants also get from the sun.

However, in our best grow lights for seedlings review you can find both types of lights.

The type of lighting isn’t the only thing you should watch out for when choosing the right grow light for your seedlings.

Factors such as temperature, brightness, amount of lumen and the size of the light can all affect your seedlings so let’s take a closer look at them

2. Heat

It’s quite obvious that the brighter the light is the more heat it emits. The heat emission isn’t always a bad thing as plants do need warmth as well as we do. That’s why heating mats for seedlings exist.

However, too much heat may cause wilting for grown plants, and for seedlings, it can stop the sprouting process entirely.

When getting grow lights for your seedlings you need to know how much heat the light is emitting and for how long you can expose your plants to that amount of heat.

A simple way to test this is by leaving your grow light on for an hour or two, and if the back of the lamp is hot to the touch, it isn’t good for your seedlings.

That’s why LED lights are the best for seedlings as they only emit a fraction of heat of what other light sources produce.

3. Brightness/Lumen

As with heat, more lumen means more brightness, and how many lumens for seedlings you need is determined by how many seedlings you have and also what type of plant you’re growing.

Seedlings of plants that need quite a lot of sun such as vegetable ones typically need around 2000 to 3000 lumen – and that’s per square foot.

So if you have 22 feet of seedlings, that means you’ll need around 2 x 2500 lumen, which is equal to 5000 lumens, so you’ll need a bigger grow light.

You can also get 2 smaller lights with 2000 – 3000 lumen each, but at the end of the day, you need to do the math on your own and see what works the best.

The level of brightness on the other hand is solely up to you.

If you think your seedlings need a constant bright light shining at them for 8 to 12 hours a day, that’s completely fine, but if you have plant seedlings that don’t enjoy the light so much, you might want to consider dimming your lights to get even and slower light exposure.

Just know that the amount of watts your light has doesn’t mean that it’s going to shine brighter, but rather how much energy it needs to light up.

4. Grow Light Size

When choosing the right size of your grow light, you need to consider two things:

  • Light fixture size – which in translation means how big is the light head and the bulbs.
  • Light emission area – which means how much area can your light cover.

As we already mentioned, around 2500 lumen is enough for one square foot of seedlings if you’re planning to just wait for them to sprout and transplant them later into larger containers.

However, if you want to light up your whole indoor garden, grow room, grow tent, and so on, you’ll need to get multiple grow lights that can cover greater areas with light.

So again, you’ll need to do the math and figure out how many grow lights you need and in which size.

It’s always better to get larger grow lights than multiple smaller ones because the larger ones will not only cover more area but will also be more energy-efficient.

Speaking of larger grow lights, fluorescent lights are usually larger than LED lights and can cover more area, but they don’t shine as bright.

They also can be placed closer to the plants, or hanged directly above them, while LED lights have to be put further away, but we’ll talk about that later.

Setting Up Grow Lights for Seedlings

how to use Grow Lights for Seedlings

So now that you know everything about which grow lights are perfect for your seedlings, now we must address the issue of setting up your grow light.

This might seem like a piece of cake, but how far should seedlings be from grow light is actually quite important as you need to assure that your seedlings get the right exposure from your grow lights.

Setting up your grow lights too close or too far will either damage the seedlings or diminish the effects of your light.

So let’s see what you need to pay close attention to when setting up your grow lights.

1. Grow Light Distance from Seedlings

This all depends on the type of light you have and also your growing conditions.

For each type of light, there is a recommended distance you should set it up so your seedlings get the best exposure while keeping them from getting damaged.

We’ll cover some most common types of grow lights and explain how to set up each one.

LED Grow Lights

Because LED grow lights are quite bright, they can cause severe damage to your plants, also known as light burn, so it’s best to keep them at a distance from your plants.

If you’re hanging your LED lights above your plants, one foot is usually enough for standard 2000 to 3000-lumen lights, but if you’re using more powerful lights, you should hang them 2 to 3 feet above the plants.

Of course, the common rule of “green” thumb is that as your plants grow taller, you want to move the lights higher.

Now, if you’re using LED grow lamps, you want to follow the same rule by keeping at least one foot of distance from the plants.

LED lights are great because even at a distance they have good light coverage, but some types of lights don’t shine as bright and can be placed closer to the plants.

Fluorescent Grow Lights

Fluorescent lights have a lot less brightness than LED ones which means the risk of your plants getting burnt is quite smaller.

Usually, gardeners place fluorescent grow lights only a couple of inches from the plants as this is the best way to make the most out of the light brightness and cover area.

However, even though fluorescent lights are larger than LED ones, you’ll still need to get a few of them for maximum coverage because they need to be placed so close to the plants.

What’s great about fluorescent lights is that they’re meant to be hanged or placed high, so setting them up isn’t so hard.

HPS Grow Lights

Even though HPS lights aren’t as popular as the previously mentioned light types, they’re still used by cannabis growers.

Same as with the LED lights, you should place the HPS light at a distance from your plants because they radiate lots of heat.

So 2 to 3 feet above the seedlings is the perfect measure.

The tricky part is that HPS lights aren’t as bright as LED or fluorescent lights so you’ll need multiple HPS lights to cover all the area.

Of course, there’s a debate whether LED lights are better than HPS lights, and you can check out our LED vs HPS grow light article for further information.

2. When Do I Put Seedlings Under Light?

As soon as you see your seeds start sprouting you should put them under your grow light. You should also use a smaller grow light at first because the sprouts are quite vulnerable and too much light can cause them to die out.

You also should never put your seedlings under dim light because once they sprout they’ll reach for the light source and dim light can’t give them the necessary nutrients they need so your plants will be underdeveloped from the start.

Of course, using different color lights to stimulate growth is always an option so you can play around and adjust your light as long as you give your sprouts lots of brightness.

3. How Long Should I Leave Grow Lights On?

This is a question of how much light do seedlings need and the answer is quite simple – they need the same amount of light as there is sunlight in a day.

Of course, depending on where you live, plant would naturally get 8 to 12 hours of sunlight a day. Because the conditions indoors are quite different for your plants, they’ll need a bit more hours of light.

When your seeds start to sprout, you should give them around 10 to even 18 hours of light depending on the type of plant.

The typical rule of thumb is giving your seedling light from 6 AM until 9 PM, about 15 hours in total, so they can enjoy 9 hours in the dark.

A great idea would be to set up a timer that automatically can turn on and off your grow light at a specific time of day.

Common Grow Light Mistakes

Common Grow Light Mistakes

So now that you know all there is about how to use grow lights for your seedlings, we want to direct your attention to some common mistakes gardeners make when setting up grow lights.

Mistakes teach us a lot, but it’s sometimes better to learn from other’s mistakes rather than your own.

So let’s see what you should avoid doing when using your grow lights for seedlings.

1. Not Enough Light

This is a problem you might face even if you’ve done everything right and it often has to do with the type of light you’re using.

But what’s even more problematic is that some grow lights are marketed as bright, and you see the voltage and you think that they have lots of lumens, but in the end, they aren’t as powerful as you’ve might’ve thought.

That’s why it’s a great idea to test out a grow light on your developed plants and see how they react so that you don’t ruin a whole batch of seedlings.

2. Not Enough Water

You would think – what does watering have to do with grow lights? However, as we already mentioned, grow lights emit heat and that heat doesn’t just affect the plant, but the soil as well.

A common problem lots of indoor gardeners face is that their plants start to wilt and they think it has something to do with the lighting, not knowing that without proper watering, the grow lights will dry out the soil leaving their plants without water.

So if you’re already going through the hassle of making a good lighting system, getting an irrigation system won’t hurt as well.

3. Too Much Light

From all the mistakes you can make using a grow light for your plants, this one is the most common, and also the deadliest.

Exposing your seeds to too much light can instantly start to damage them and they might not sprout at all.

That’s why you need to keep your lights at a distance and make sure they have the right amount of lumen.

If you’re not sure if your lights are too harsh for your seeds, you should make sure they’re at least 2 to 4 feet away from your seeds.

4. Turning Off Grow Lights During The Day

You should never turn off your grow lights during the day even if your plants are getting some sunlight.

Because they’re already indoors, your plants are acclimated to the environment you’ve set for them. This means that right from the start of their life cycle (germination), you need to give them consistent light so that they can adapt to the set conditions.

As with humans, plants need time to rest and “sleep” as when they’re in the dark they start to mature and they use fewer nutrients because they’re saving them up for the next sunrise.

So because your grow light acts like the sun, it’s crucial that you turn on and off your lights at the exact time.


So you now know everything about how to use your grow light and how much light for seedlings is necessary for their proper development,

We hope you’ve enjoyed our review, and be sure to follow our suggestions so that your plants get the love they deserve.

Happy gardening!