Plant Care 101: Light Tolerance & Variance

Direct vs. Indirect Sun

We briefly discussed light in the introduction to this series, and at the risk of information overload, the most important point we like to make is that bright indirect light is a good target for light. Plants will grow faster, be more full, and if they can, may even flower when given sufficient light. 

We’ll touch more on seasonal shifts in a future post, but depending on the season, window direction, time of day, window types and treatments, we typically advise against placing houseplants in direct sun, or outside, and recommend south facing windows if available. Rooms that are bright with ambient light bouncing around are also excellent for plant placement.

Of course there will be exceptions such as cacti & succulent type plants, and we have found that morning light from the east tends to be more gentle before the sun heats up in midday, so there will be a fair amount of variance in each home you’ll find through experimentation.

An unfortunately common occurrence in Sacramento is the summertime afternoon sun: leaving plants in the direct sun can and has sunburned plants (and people!) so it’s usually a good idea to pull plants in these environments further back from the windows into the room, or draw a curtain over west facing windows.

“Tell me what you want, what you really, really want!”

A common problem we see in customer plants brought to the Plant Lab is etiolation due to insufficient light:

Etiolation [ ē′tē-ə-lā′shən ] :
A pathological condition of plants that grow in places that provide insufficient light, as under stones. It is [often[ characterized by elongated stems and pale color.

For more reading on etiolation, we recommend Wikipedia: https://en.wikipedia.org/wiki/Etiolation

These plants will have long stems with leaves spaced further apart than normal, fall over from their planters, or send out long, thin “runner” vines with small leaves. As cell structure tends to be weak in etiolated plants, they are commonly very thin and fragile. This situation is not ideal and usually results in needing to start over with the correct light, but learning to identify what a plant needs is a huge part of the experience in houseplants and will help in the future.

Some plants have developed the ability to survive in lower light conditions. Typically coupled with drought tolerant traits such as thick leathery leaves, sturdy trunks/stems to store water, or rhizomes under the soil, these plants will have deep dark green leaves, full of chlorophyll ready to absorb available light. Snake plants (Sansevieria), ZZ Plants (Zamioculas zamiifolia) and Chinese Evergreen (Aglaonema) are good examples of this.

It’s important to note that low light tolerant plants are just that - tolerant - but sometimes shouldn’t be expected to grow quickly. As such, we may not need to water these plants very frequently. If moved to brighter environments, they will thank you with more growth!

The inverse of low light tolerant plants will be “variegated” or non-green colored leaves. This absence of chlorophyll will require extra bright or even supplemental light for success. Without sufficient light, variegated leaves can die back. While some plants can produce additional chlorophyll for new leaves they will be more green and typically smaller as the plant manages its resources to survive. It’s usually best to give these plants the better/brighter spots in your home to get the optimal growth from your variegated plants.

The dark green leaves of the ZZ Plant (left) are very efficient, making it an excellent choice for low light environments. The lighter leaves on the variegated ‘Tineke’ Ficus Elastica (right) require bright light.

Depending on where you live, you may experience shifts in available light as seasons change.
Check your windows seasonally and see if your plant might need a “winter home”.

During Fall and Winter months when light is comparatively unavailable many houseplants will slow growth to a minimum and our care will shift into maintenance mode. We’ll hold back on watering frequency, and might need to increase humidity with humidifiers or pebble trays as the heaters are turned on and wick moisture out of the air. We may need to find more light at home or even add extra light sources.