Confused about grow lights – House Plant Journal

Confused about grow lights

Plant Parent

I have a grow light question, I’m worried that some of my plants that require more indirect than direct light are getting too much.

I’ve read through your articles but am still a bit confused. I have the same T5 bulbs from amazon as you and they are on 8 hours a day.

Do the plants requiring more indirect light need something to filter the light before it hits them or are they OK as long as the FC isn’t too high?

Is there such thing as 400FC in direct light and 400 FC in indirect light or is it considered indirect once the light hits a certain number?

Recently had to move and change my whole plant set up so now everything is under the lights (in a basement with barely any natural light).

I do have my handy dandy light meter!


This is a very good question because it helps me understand what people are confused about.

“Light” should not be considered the same as “sun”.

If the sun shines directly on a light meter, it will measure anywhere between 4000 to 10,000 FC.

If the sun is blocked by a white curtain, it will measure around 1000 to 3000 FC.

Light shining from a grow light needs to be measured because every inch of distance can change the reading by a few hundred FC.

Most plants that want “bright indirect light” will be perfectly fine at a distance where you measure the grow light to be 400 to 800 FC. The distinction of whether a grow light shines “directly” or “indirectly” is meaningless and causes confusions like this 🙂

The only meaningful use of the terms “direct” and “indirect” refers to the SUN.

Hope that helps.

Plant Parent

That is super helpful thank you!

Much less worried about my plants now 🙂


If you’re into houseplants for the long-term, I’ve created the perfect course for you!

Tired of your houseplants dying on you?

3 responses to “Confused about grow lights”

  1. This is great info!
    I just finished sending an email to you containing some of these same questions as well as a few others and now I have some answers!

Leave a Reply

Your email address will not be published. Required fields are marked *