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Seedling Under Light

How close to put a light to plants?

When we see the first signs of spring we all get excited to start seed.  There are a few things that you need to know when starting seeds to ensure healthy seedlings.  The first question is how close to put a light above seedlings?

how close do you put grow lights

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Before we talk how close light needs to be lets talk about when you need a light.

When you first plant your seeds there is no need for a light.  Allow the seeds to germinate before you turn your grow light on.  Seeds do not need light to find their way to the surface.

As soon as the seeds emerge from the soil you need to add your grow light very close.

how to light seedlings
seedling emerging from a seed

What kind of light do seedlings need?

It is important to remember that you need to have a grow light!  No matter how bright your light bulb is, if it is not a light in the right color spectrum for plants it will not help even if you put the light close.

Your seedlings will get some limited light from a bright general use light however they will grow weak and leggy.  If you don’t have a grow light than a really sunny south window will do more for your plants than a general use light bulb.

Check out lots of unique grow lights at Sow Good Naturally on Etsy

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What is a Grow light?

Grow lights are light that give off the right light spectrum.  Your plants need certain “color” of lights.

All light is a combination of colors.  A rainbow is a demonstration on the colors in normal light.

how close to light should I put seedlings
plant need each end of the spectrum but not much in the middle


Your plants mostly use the red and blue light spectrum.  This is why many grow lights are red/blue.  You can have a grow light that looks white.  These lights look great for us however your plants are still using mostly red and blue light.  Remember it doesn’t matter how close your light is if it is the wrong kind of light.

For more about grow lights please read The best lights for indoor gardens

LED, Florescent or Incandescent: know will determine how close the light needs to be

All the information refers to GROW LIGHTS specifically not general purpose lights.

There is one more important thing to decide about your grow light height before you can get the perfect set up.  Is your light an LED, a florescent, or an incandescent.  This will effect how close the light needs to be.

For the most part incandescent grow lights are not used much.  They tend to be too expensive to run, have a short life spend and don’t give the best light to your plants.

Most people will chose between LED and florescent.  For this article we will keep it basic.

Both offer good lighting to your plants

LEDs are more expensive to buy but offer the longest lasting and lest expensive to run.

Fluorescents are less expensive up front up will not last as long and cost a bit more to run.

Why do you need to know what type of light you have?

These lights need to be used at different heights from your seedling or plants to be effective. So that means you need to determine your light to know how close to put it to your plants.

LED lights are the most intense and can be used 8″ to 12″ above your seedlings and plants

Fluorescents light are less intense so they need to be 4″ to 6″ above your seedlings and plants.

In either case you can put your light closer but NOT father away.  The increase distance will quickly diminish.

seedling under light


You can put your light closer than the recommended .  However keep in mind that all lights give off heat.  Your young seedlings are sensitive to environment conditions.  So check the temperature under the light to make sure you are not burning you seedlings.

This heat can be helpful if you are starting your seeds in a cooler place.  The added heat can help them grow.


How much coverage does one close light give your seedlings?

Again that will depend on the type of light that you use.  We now know how close to put the light but how far does it reach side ways?

The side distance  between the lights should be the same as the distance from your seedling.  IE  LED lights can be 8″ to 12″ apart and fluorescents should be 4″ to 6′ apart.

That is just a guide.  The best way is to turn your lights on in an otherwise dark area.  Look at what the foot print of the light coverage is.  Your light will be effective within that foot print as long as the total distance to the actual light source is not farther than the recommended range.  If all your plants are close enough for the light to reach all leaves at the proper distance then your light is perfect!


I hope you found this helpful.  Please check out some other of our posts and leave comments or questions.

Happy Growing

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