When we talk about gardening indoors we usually use different terminology than we do for outdoor gardening (see part 1), here we will discuss indoor lighting and how this translates to your gardening experience. It's no secret that plants need light to grow, but how they get that light and how much depends on the plant you are growing. Some plants are more forgiving and will tolerate nearly any amount of light while others have very specific lighting needs. We're also going to discuss lumens and light spectrums next weeks and how those influence plant growth and production, since plants use different wavelengths of light to grow and to produce flowers and fruit - so stay tuned.
Indoor Gardening:
One of the most important things to remember when growing plants indoors is that this goes fundamentally against nature - plants grow outside in a wide range of environments! When we bring them inside we need to be even more aware of how access to natural and supplemental lighting such as grow bulbs (and even household lighting) effects their growth. Much like growing plants in the wrong zone, growing tropical, desert, or temperate plants inside is a challenge - one that doesn't stop at Light, our next series will focus on heat, humidity and airflow, but for now let's focus on photosynthesis.
Direct light:
Outdoor plants usually get some direct sun, even if we say they grow in full shade, when we bring plants indoors we need to pay attention to what their outdoor growing conditions are in nature and translate that into indoor growing conditions. However a South or West Facing window indoors can still provide direct sun - and if your glass doesn't have a UV filter or barrier it can actually be more intense than the same sunlight just outside that window. So unless we're growing a plant that likes full sun outdoors such as a tree or flowering bush, let's be careful to make sure we don't sunburn our plants.
Indirect light:
Might seem like a no brainer but not all light is created equally. When we're gardening indoors we're usually discussing the intensity of indirect light; high, medium or low. If we say low light we never mean no light - if you're working with a space with no natural or very poor natural light stay tuned for next week's discussion on light spectrums and artificial lighting.
The white paper test:
Grab a sheet of plain white paper, turn off your lights and walk around, go to areas you want to put plants - hold up your sheet of paper and place your hand in front of it with your hand facing the direction the light comes from, look at the shadow on the paper - if it's crisply defined that space is bright, if you can feel the heat of the sun it's likely direct light, if not it's indirect light, if it's fuzzy around the edges of the shadow it's medium, if it's faint or non existent but the room still has plenty of ambient natural light it's low light.
Simple right? Let's look a little closer anyways, since the sun moves that light will change, do this test 3 times in one day, morning, afternoon and evening - you're likely going to get a different result every time. So let's explore how we define light intensity indoors and why it changes sometimes drastically based on window directionality.
Bright Indirect Light
Medium Filtered Light
Low Light:
Intensity & Directionality:
As we see above the intensity of indirect light for indoor gardening is usually discussed as high, medium, and low light. Next week we will cover a more scientific breakdown of light intensity in terms of lumens and spectrum but for now we're going to focus on these basic concepts and how to identify these three lighting catagories and what they mean for indoor plants. We can usually predict how intense the light is by looking at which direction it's coming from - same as outdoors we know that the all day sunlight from the South and West is usually more intense than morning sun from the East, and certainly more intense than the ambient sunlight from the North. So let's take a closer look at Directionality of the light source and how that informs our choices for placing plants indoors.
Northern Light:
Usually provides little ambient lighting - plants can usually be placed on a windowsill or next to it for medium light if the room stays bright all day, or low light if the room tends towards being dim. These rooms may need a boost of artificial lighting if you hope to place plants any further into the room or if you plan on keeping sun loving plants.
Eastern Light:
Usually provides medium filtered Light in the morning and low light as the day wears on. Minimal risk of sunburn to light sensitive plants occurs near the window, but be cautious - as the day wears on that light quickly disappears leaving you with less than ideal conditions for sun loving plants. Artificial lighting in the afternoons can supplement plants who might otherwise feel short changed.
Southern Light:
Generally fills a room with bright and medium indirect light all day, the closer to the window you get the higher the risk of sunburn to sensitive plants, so reserve those first couple of feet by the window for true bright light lovers. Of you're worried about sunburn you can always add a sheer curtain to diffuse and filter the light. Far corners of these rooms may still be low light.
Western Light:
Fills the room with bright and medium indirect light all afternoon, be careful close to the window as sunburns can happen to sensitive plants easily from western windows the sun is usually the most intense from this direction, a sheer curtain can certainly cut down on that risk without losing much light throughout the room. Same as above, far corners may still be low light.
So now you know a bit more about indoor light and how the direction windows face translates to basic understanding of lighting, it's time to break out that paper and get to work planning your next plant space! Stay tuned for next week where we will break down artificial lighting and color spectrums to help you grow the best plants year round.
Our next series will be on heat, humidity and airflow.