GROW LIGHTS HELP GIVE PLANTS A BRIGHT FUTURE
There is a general rule of thumb that we use in the greenhouse for lighting plants. It states that for every one per cent reduction in light there is a one per cent reduction in plant growth. And whether or not one is growing plants in a greenhouse or in a home the same principle applies.
In our homes, we are not necessarily trying to maximize plant growth, but we are certainly striving to grow robust, healthy plants. And that is a challenge that we face during the short, dark days of winter as our houseplants struggle to receive enough light energy to keep them healthy and happy.
The good news is that there are a few simple things that we can do to provide them with a bright future. A bit of science: The amount of light that houseplants receive in our homes is pretty much limited to the amount of light that can penetrate through our windows and skylights. The push toward increased energy conservation has led to some excellent glazing
materials in our homes that dramatically reduce heat loss compared to the ‘good old days.’
I remember sitting by the single-pane, wooden-framed windows in our farmhouse when I was a kid and feeling like I was going to freeze to death on cold winter days. Today, these leaky, energy-inefficient windows are pretty much long gone — replaced by very energy-efficient windows. But this increased efficiency can be a bit costly to the health of our houseplants.
While single-pane glass was terrible at keeping the cold out, it allowed transmission of about 90 per cent of the sunlight striking them into our homes. Today, some of the super energy-efficient glass transmits as little as 40 per cent of the sunlight it receives. As a result, that cherished Christmas cactus that your grandmother nurtured for decades and handed down to you may not look all that great in the depths of winter near your quadruple-pane glass windows.
Plants are very adept at sensing the diminishing light levels in their environment and doing their best to adapt to whatever light they receive so that they can at least survive. Some plants will drop leaves that were generated when light levels were greater, and then replace them with leaves that are better adapted to shadier conditions.
Typically, as light levels drop plants produce thinner, wider leaves, with the hope that these broader leaves can capture more sunlight. But when lights levels drop too low for an extended time this strategy often fails, and the affected plant is destined for the composter.
WHAT SHOULD YOU DO?
There are only a couple of strategies for keeping plants healthy during the winter months: move them closer to the windows, if possible, or install some supplemental lighting.
Moving plants closer to windows during winter does help, but close proximity to a window is often not enough. Supplemental or ‘grow’ lights are still the best solution to the paucity of winter sunlight and they are very easy to install. Essentially, you just need to support the lights and plug them in. I use both T5 fluorescent tubes at home (T5 tubes are the skinny ones) and spiral grow lights — depending on the plant species and where the plants are located.
Relatively new to the market are LED (light emitting diode) grow lights. An easy way to think of LED lights is to envision a computer chip that lights up. They are more expensive than T5 tubes but they last much longer and are more energy-efficient. In fact, I tested a two-foot-long LED and did the calculation on its energy usage. To make a long story short, if I ran the LED 12 hours a day, seven days a week for a year the annual energy cost was only about four dollars.
Now, a couple of criticisms that some people have with grow lights is that they aren’t all that pretty and the lights can be pretty darned bright. I tend to agree. But one reasonably simple solution if you don’t like having grow lights front and centre in your living room is to, instead, think about giving your houseplants a ‘light vacation’. In other words, place a grow light over your houseplants periodically or move the plants to a spot in the house where they can be bathed in light for several hours. You’ll be amazed at how much your plants will appreciate their vacation and will respond with richer, thicker growth.
Finally, don’t forget that while many of our plants suffer from PAD (photosynthetically affective disorder) during the winter many of us suffer from SAD (seasonally affective disorder) during the darkest days of winter. Scientific studies show that grow lights are not only great for combating PAD in plants but do a great job of fighting SAD in humans.
This winter, it would be a good idea to grab a book, your houseplants and a grow light and immerse yourself and your botanical friends in some light. While your dog or cat likes receiving tasty treats, your houseplants love nothing better than to be engulfed in a few billion photons of light.