Home > Great Big Greenhouse Blog > June 2013 > Who Turned Out The Light?

Who Turned Out The Light?

One of the most difficult of plant requirements to discuss is light. If you remember your grade school science, plants have to make their food…photosynthesis. The energy they use to do this is sunlight. Gotta have it!
 
The problem is that remembering or describing the light in a particular location within your home of office is like remembering a shade of green (a customer recently compared this to shopping for thread without bringing a sample of the cloth.)  So we try to get at this information by asking questions like “which direction does your window face?” The answers can be pretty funny. Replies range from “It’s a kitchen window” to “It faces Ashland” to a quick disorienting spin in a circle with a triumphant gesture accompanied by “THAT WAY!” Many customers tell me that the plant he or she wants will get the same light we are both standing in here in the greenhouse, and I ask if he or she has a plastic roof (no one has ever said yes, although that would be cool!) Almost everyone seems to think that they have “full sun” if they are not tripping over the furniture. If every window’s exposure was full sun, we would be living in something akin to flatland.
 
When talking gardening, we have some specific terminology regarding light. Full sun, for instance, means direct sun for six or more hours. With direct sun, you can set something on fire with a magnifying glass, or at my house you see dust swirling in the beams. Part sun is direct sun for less than six hours. Shade is the absence of direct sun.  We don’t use the term “shade” when talking about houseplants, however, because almost everywhere inside is shade (walls, roof, etc.) We break it down into bright filtered or bright indirect light to medium to lower indirect light. A plant will rarely receive direct sun unless it is sitting on the windowsill. 
 
It would be easier to identify the amount of light a plant would receive if people knew the orientation of their windows. North-facing windows never get direct sunlight, while unobstructed south-facing windows can receive direct sun most of the day. A morning sun eastern exposure is great for most foliage and some blooming houseplants—it is sunny but not hot. And a western exposure is sunny in the afternoon and probably too hot for many foliage plants. As soon as you add blinds, shades, sheers, or perhaps leafy trees just outside, you need to downgrade to indirect light. Even with a sunny window, the area next to the window is much darker as the wall will cast a shadow on any plant not directly in front of the window.
 
Fortunately, there are many foliage plants that are happy in indirect or filtered light. Most of our popular houseplants grow in rain forests or other shady locations, and are adapted to little or no direct sunlight. It is very different with flowering plants—most need some direct sun, if not full sun. And many succulent houseplants will grow better and more compactly in direct sun. We try to label all of our houseplants with a light requirement. It will specify whether the plant needs any direct sun, or if it is happy with bright or moderate indirect light, or even if it is tolerant of lower light levels. Choosing the right plant for the available light will help you be a more successful indoor gardener.
 
P.S.: While a table lamp next to your arm chair will help you read a good book, it is not sufficient for growing the ficus tree across the room. I’ll discuss supplementing natural light with artificial light in the next blog.
Posted: 6/1/2013 by Margot | with 0 comment(s)
Filed under: MargotGunn, TheGreatIndoors
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