Finding Your Inner Light
Ellen Zachos
How do your houseplants look? Are they full, luscious, and healthy, or do they look a little scrawny? If your plants don’t look quite as wonderful as they did when you first brought them home, maybe they’re not getting enough light. How do you know? Ask yourself a few questions:
- Are the newest leaves smaller than the leaves your plant had when you bought it?
- Are the leaves a darker green than they were originally, or if the plant had variegated leaves, are the new leaves less colorful?
- Are new leaves spaced further apart than older leaves, making the plant look leggy?
If you answered yes to any of these questions, your plants may not be getting enough light.
Growing under artificial lights is easy. There are just three basic things to understand: color, intensity, and duration.
Color: Red, orange, yellow, green, blue, indigo, violet are the colors of the visible light spectrum. The sun emits light in all these colors, but light in the blue and red ranges is most important for plant growth. Flowering plants need orange/red light in order to bloom, and blue light promotes lush growth of foliage plants.
Intensity: Light intensity (brightness) is the single most important factor in growing plants indoors. Low light intensity produces leggy, weak plant growth, and few or no flowers and fruit. Most people don’t understand how much less intense indoor light is than outdoor light. The light on a sunny windowsill is a fraction of what it would be outdoors, just on the other side of the glass. Fortunately, a lot of great houseplants are native to the rainforest floor, and qualify as low or medium light plants.
Duration: This refers to the number of hours of light your plants get per day. Artificial light doesn’t precisely duplicate sunlight, so we compensate by giving plants more hours of light indoors than they would get outdoors, making up for reduced quality with increased quantity.
Don’t keep the lights on 24/7. Plants need some uninterrupted darkness in order to flower. For most houseplants, you don’t need to worry about exactly how many hours they need. Just remember that certain chemical processes only take place in darkness; a plant given light around the clock will not thrive indefinitely.
There’s a wide range of grow bulbs available today. Incandescent bulbs, some compact fluorescent bulbs, and fluorescent tubes fit into normal, household fixtures. High Intensity Discharge and large compact fluorescent bulbs require special fixtures.
Before you choose what kind of light to buy, consider four things:
- What do you want to grow under the light?
- What style light fixture will fit your space?
- What color of light is most agreeable to you?
- How much do you want to spend?
Fluorescent tubes are good for growing low light plants, like creeping fig and many philodendrons. They’re inexpensive to buy and run. They’re very efficient, giving off most of their energy as light and very little as heat. You can place plants close to the tubes (six to eight inches away) without worrying about foliage burn.
Bulbs come in standard lengths of 24″ or 48″. Cool white tubes give off a blue-white light, while warm bulbs produce a light with a slightly red color. Full-spectrum fluorescent tubes emit a light that resembles noonday sun. Fluorescent lights are most efficient when used with metal reflectors that direct light toward the plants, so the fixtures tend to look rather industrial.
Plants placed at the ends of the tubes receive less light than those at the center, so put your lowest light plants at either end of the tubes. Replace your fluorescent tubes every eighteen months.
Small compact fluorescent bulbs fit into incandescent fixtures and are perfect for spotlighting low light plants. Hang a single fixture on the wall and aim it directly at your plant. Like fluorescent tubes, these bulbs can be placed about eight inches from plant foliage.
Incandescent bulbs are less efficient than fluorescent; a lot of energy is given off as heat, rather than light, so keep your plants at least twenty-four inches away from the light source. These bulbs give off a yellow-white light that looks normal in your home, as opposed to the more institutional look of fluorescent light. They’re best for growing low light foliage plants. If a corner of your apartment calls for a single specimen plant, try a cast iron plant or a snake plant under an incandescent grow bulb. Or use several incandescent bulbs in a track light fixture.
High Intensity Discharge (HID) lights are the gold standard when it comes to growing plants under artificial light. They are the brightest available, and you can grow just about anything under them. Plants should be placed at least twelve inches from the bulbs.
Metal halide (MH) bulbs give off light that looks slightly bluer than daylight. They promote compact, leafy growth and are a good choice for a living space, since the light isn’t highly colored (although it’s VERY bright). Metal halide bulbs need to be replaced about once a year.
High pressure sodium (HPS) bulbs last about twice as long as metal halide lamps but cost slightly more. They promote flowers and fruit, and their light is reddish yellow, giving everything a distinctly sallow color. This isn’t a great choice for your living room!
HID lights run off regular 110v household current but require special fixtures with ballasts. You can’t just screw them into any old fixture, and MH and HPS bulbs are not interchangeable. A metal halide bulb cannot be used in a high pressure sodium fixture, and vice versa. If you’re tempted, try a small, self-contained HID system with a 100 watt bulb. It’s a plug-and-go set up and lights a three foot wide window with two shelves of plants.
Large compact fluorescent bulbs are less expensive than HID set-ups. They, too, require their own fixtures, which are about the same size as the small HID lights. The bulbs come in several colors (cool and warm). I prefer the cool for my living room. The warm isn’t as strongly colored as an HPS bulb, but it’s still very yellow. Light output is less intense than that of HID lamps, but you can grow a wide selection of medium and low light plants under these bulbs.
For an isolated small spot of high light, try an Agrosun Power Gro Bulb. It’s a mercury vapor light (150 watt) with a broader spectrum and more intense output than incandescent or fluorescent grow bulbs, but a smaller footprint than an HID fixture. It’s self-ballasted and can be used in a floodlight type lamp with a ceramic socket. This is a hot bulb, so keep your foliage at a safe distance from the fixture (at least twenty-four inches). It’s an excellent choice for adding light to an indoor herb garden.
Adding artificial light to your indoor garden is easy and lets you grow wonderful plants all year round. Isn’t that worth a try?
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