A Quick Guide to Measuring Light for Plants

When you have a plant that is withering away instead of growing strong and beautiful, your first thought may be that you’re not caring for it correctly. Maybe it’s not getting enough water or fertilizer; maybe you’re giving it too much attention.

A fundamental and commonly overlooked issue is where the plant is placed and how much light it’s receiving, though.

It’s easy to get confused about how much light you have in your home. What’s the difference between low, medium and high light? How do you figure out which one you have?

Plants are an investment.

Our recent custom design and plantscaping work has reminded all of us just how important light and placement is for the health of plants.

One of our beloved clients first contacted us with a common problem: they had dozens of plants decorating their gorgeous interiors, but every day they have to trim leaves that are browning. They called us in to troubleshoot and to use our own plantscaping expertise.

When you’re ordering and maintaining plants at that level, they’re much more than an aesthetic nicety – they’re an investment, and you need quick reassessing of light and repositioning of the plants in order to make sure that investment is protected.

Our advice is to thoroughly evaluate the proper light needed for each plant type. Here’s how:

Don’t trust your eye.

First, we auto-compensate for brightness and darkness. Second, indoor lights can confuse how naturally bright an area truly is.

Do a shadow test.

While this isn’t a precise way to determine light, it’s quick and can give you a rough idea of what you’re working with.

Find a spot where you’d like to place your plant. At noon (when the sky is highest in the sky, giving the most direct light), hold your hand to the light and look at the shadow you create.

A crisp, well-defined, high-contrast shadow means high light. A faint, not-well-defined shadow means low light.

Use a light measurement app.

For a more scientific reading, the Light Meter app measures foot candles (FC), which is the unit of measurement used to measure lighting specifically for plants. This article provides a great how-to for using the app. Generally, plants that need low light are fine with 25 FC, while plants that need a lot of light need 150 FC or more.

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