The busy days of the holiday season have passed and most of the holiday related greenery is out the door. Our outdoor gardens are nestled to bed under the snow. So to appease our green thumbs and our urges to play in the dirt, and to add some color to our otherwise dull post-holiday décor, let’s turn our attention to houseplants.
The most limiting factor in the growing healthy, vigorous plants in the indoor environment is light, especially in the northern climate. Light is needed for the process of photosynthesis where carbon dioxide (CO₂) and water (H₂O) are converted to carbohydrates (energy). Plants use this energy (food) to grow, bloom and produce seed. Without light energy cannot be produced and without new energy plants will use up what they have stored and then die.
There are three things to consider when talking about ‘enough’ light for houseplants; the intensity (brightness), the duration (number of hours) and the quality of the light. Sunlight in our climate fluctuates widely both in duration and intensity from season to season. The quality of light involves the wavelengths or colors. Sunlight provides all wavelengths; red, orange, yellow, green blue, indigo and violet. Plants use the red and blue wavelengths; blue for foliage growth and red for budding. If your home environment doesn’t provide enough sunlight you can provide supplement light. Fluorescent lighting can provide additional lighting for your houseplants during the winter months; use a fluorescent shop light hanging 10 to 12 inches above if you have a number of plants or a single fluorescent bulb for a single plant. LED grow lights provide primarily red and blue light that is needed by the plants. Additional lighting should be provided between 6 to 10 p.m.
So what is the right amount of light needed for our plants? That really depends on the plant. Low light plants are generally those which grow in nature as understory plants; that is they grow under the canopy of taller plants. Common houseplants that could be considered low light plants are parlor palms, English ivy, philodendron, peace lily, pothos or dracaena. These plants can survive in a north window or in a corner with supplemental light from a single fluorescent bulb. Low light plants do not dry out very fast so be sure to check the soil to make sure it is dry before watering.
Medium light plants such as amaryllis, Boston ivy, rubber plants, spider plants, jade plants, Swedish ivy and African violets require a little more light. They could thrive in an east facing window or a west facing window away from the direct light. Or a couple of fluorescent bulbs could provide enough supplemental lighting. The same is true for medium light plants with regards to watering – the soil does not dry out quickly so don’t over water.
High light plants require the most light and consequently the soil does tend to dry out more quickly. They will need more frequent watering. They will need a south or southwest facing window or more supplemental lighting. High light plants would include culinary herbs such as basil, thyme or rosemary, cacti and succulents, hibiscus, geraniums and poinsettias.
There are several signs to look for that your plants are not getting enough light. A lack of light will mean that a plant cannot produce chlorophyll which is what makes the plant green, so it may fade to light green, yellow or even white. Plants can become leggy which means long, thin stems as a plant reaches for the available sunlight. Or there will be long spaces between the leaf nodes. Lack of light can cause plants to drop leaves, especially older ones or variegated plants can turn to a solid color. And often lack of light can prevent flowering plants from flowering.
I hope this will help you to arrange your plants in the optimum places for growth in your home or to choose the appropriate plants that you might want to add to your interior landscape.