Tag Archives: light

Projects: Supplemental Indoor Light for Carnivores, For Work and Home

Thoughts during ongoing COVID-19 self-quarantine: sooner or later, no matter what happens with a vaccine or other long term solution, we’re all going back to something we’ll collectively call “normal”. Whether we continue to shelter-in-place or start to go out, one absolute is that a need for green will only become more intense. Sure, we’re in the middle of spring in the Northern Hemisphere, but what happens in autumn and winter, or summer in lower latitudes when the heat becomes too oppressive to stay outside for long? What about the need for green for those working night shifts, where they’d like to have a flora break outside of normal daylight hours? And what about those going back to desk jobs, where the only time they see outside is when they arrive and when they leave?

Well, the good news is that while not all carnivorous plants do well indoors, some do. Trying to raise Venus flytraps or North American pitcher plants indoors is folly: besides their need for a winter dormancy, they require more light than is practical for anyone not running a cannabis grow room. Many tropical species do rather well under consistent room temperature, though, but the biggest issue indoors is with light. Most office buildings constructed after 1990 have window treatments intended to minimize light input, especially in warmer areas, and the typical office lights in those offices work for only the most shade-loving plants such as spathophyllums and philodendrons. Carnivores need considerably more light output, and until very recently, that sort of light output both generated considerably more heat than was acceptable and used too much power to do so. For the last five years, though, the humble LED light bulb offers a perfect solution.

To start, you’ll need a classic desk lamp. These are available new, used, and antique, with all sorts of features with the new lamps such as USB plugs for charging small electronic devices and additional three-prong plugs for devinces requiring more power. (Should you have permission and/or interest, these plugs facilitate setting up webcams to show off your plant at any time, but that’s up to you.) The only absolute is that the lamp has to have a standard screw light socket: everything else depends upon circumstances.

Now, a lot of proprietary full-spectrum lights are available both for plants and for such hobbies as needlepoint or model-building, and the light fixtures themselves are often available for really reasonable prices, both new and used. The catch is that the bulbs are most often fluorescent, and they aren’t designed for running every day for hours at a time. The overwhelming majority of fluorescent fixtures, either tube or compact fluorescent, have a distinctive drop in light output after a few months: they still appear to be nice and bright to human eyes six months later, but they’ve usually decreased their light output by 50 percent or more, and that keeps dropping as the months go by. Three years after installing one, the light produced by a typical fluorescent bulb will be suitable for growing ferns, fungi, and not much else. Those daylight and full-spectrum fluorescent lights are also exceedingly expensive to replace, with some having replacement bulbs that are so expensive that buying a whole new lamp is often a cheaper option. These lamps also have proprietary sockets that prevent you from installing other bulbs or tubes, and the most practical option is getting one of the lamps that accepts screw-type bulbs that’s been standard since Thomas Edison’s day.

No, the secret is going with LED bulbs. At the beginning of the last decade, before the mass manufacture of white Light Emitting Diodes, your standard plant lights were those red and blue combos for indoor gardening and Sticking It To The Man. At that time, the idea was that daylight produced a specific ratio of red photons to blue photons: red photons have a shorter wavelength and therefore less energy but sunlight produces so many more, and blue photons are more energetic but much less common. Chlorophyll molecules can use the energy from both red and blue photons, and the mass production of blue LEDs in the early 2000s meant that LEDs could be used for high-intensity plant grow lights for the first time. You won’t need anything that specific unless you really like the look, and standard LED light bulbs are both considerably cheaper and easier to obtain.

Now the other thing to consider is the output. LEDs have the advantages of not dropping in light output with time the way fluorescents do, putting out far less of their energy consumption as heat, and having a much longer practical lifespan. Running for 12 hours a day on average, a typical LED bulb will last upwards of five years before finally expiring, as opposed to six months before fluorescents need to be replaced. In a workplace or home desk environment, white LED bulbs make a lot more sense.

From there, it’s a matter of looking for light output. For the most part, LEDs come in full-spectrum, warm white, and cool white options, with the full-spectrum bulbs usually costing a bit more. Aside from that, it’s whatever moves you and makes your plant look its best. The important consideration is the actual number of lumens (the standard measurement for light output) being emitted, and most bulbs are handily labeled for such. A perfect light output for small carnivorous plant containers is about 1600 lumens, but if you can’t remember that, the labels on most LED packages offer a handy alternative. Almost always in the upper right corner, those packages list the light output equivalent of an old-style incandescent bulb, and what you want to get is a 100-watt equivalent. The actual power consumption will be between 13 and 17 watts, depending upon the brand and the particular colors inherent in the light (full-spectrum LED bulbs tend toward 17 watts), but the light output will be the same. Whatever light option you want, get a 100-watt equivalent, and screw it into your desk lamp.

IMPORTANT: Go for a 100-watt equivalent LED bulb, not an actual 100-watt LED bulb. Not only is that amount of power consumption not necessary, but most desk lamps were designed for 40 to 60 watts of power consumption. While the bulb may not be throwing off the ridiculous amounts of heat that an old 100-watt incandescent bulb did, the wiring and socket can overheat and become a fire risk.

LED bulbs produce less heat than compact fluorescent bulbs and a lot less than old-style incandescent bulbs, but they’ll still generate some heat. Therefore, unless your workspace is considerably colder than most, and I’ve worked in some horrendously cold offices, set your lamp head about a handspan away from your plant and turn it on. If you want to get fancy or to make sure your plant gets light over the weekend or over vacation, consider getting a timer, analog or digital, to set the light output to match day/night hours over the year. With this setup, it’s possible to keep many species of Asian pitcher plant and tropical sundews, butterworts, and bladderworts well away from other available light sources.

A few things to consider:

  • Many offices turn off air conditioning over the weekend as a cost-saving measure, and some carnivores such as Cape sundews (Drosera capensis) have issues with temperatures going above 26 degrees C/80F. Cape sundews react to excessive heat, either from the light or from other sources, by burning back, and Asian pitcher plant leaves turn a brassy color when getting too much light. If these happen, pull back the lamp another handspan and watch to see if the situation improves.
  • Even though you and your plant may enjoy the high levels of light from your lamp, coworkers and supervisors may not, and this situation is particularly exacerbated in the ongoing nightmare of the open office. To keep stray light from annoying coworkers and control freaks alike, consider using a light shield made of cardboard, polycarbonate plastic (old political campaign banners cut to size and painted work well), or Mylar to keep the light reflecting back on the plant and not in coworker eyes.
  • In a typical work environment, you may get well-meaning coworkers or security crew who see a light on without you at the desk, and think they’re doing you a favor by turning it off, or busybodies who don’t like having it left on over the weekend. Signage can minimize a lot of this, even if it’s a sign over the light switch reading “This Light Is Running On Purpose.”
  • It may be perfectly obvious that the light is there for a carnivorous plant, but take into account roommates, coworkers, and supervisors with a phobia of reptiles or arthropods that might assume that your container is a home for a snake or insect. Again, a sign or tag stating “Nothing But Us Plants” is a good idea, as well as one reading “Please Do Not Feed Me” for those who decide they want to watch your plant feed and drop in whatever they find. If they keep it up anyway, well, at least you have a portable lamp to move your plant to home…or to work.

Observations: “Avoiding All Puns Involving Light”

Okay, so your Venus flytrap or pitcher plant is having problems. You’ve looked at the growing mix in its pot, making sure that the sphagnum moss and silica sand are in the right proportions and not contaminated with green moss or anything else that might cause its untimely death. You’ve done the same thing with the water, making sure that you’re using either distilled or rain water if your local municipal water is too mineral laden. (You also already know that boiling tap water won’t get rid of dissolved minerals unless you’re running a still.) Even so, the plant is either declining, either growing long and lanky or pale, or it’s dying. You’ve checked the pH of the soil mix, you’ve checked on drainage if the plant doesn’t like sitting in water, and you’ve checked over and over for possible fertilizer contamination. So what else?

Well, have you looked at the light? I didn’t think so.

It’s funny that the most important aspect that distinguishes plants from animals or fungi, the ability to take water, carbon dioxide, and light and turn them into stored energy via photosynthesis, is also the aspect that gets neglected the most because it doesn’t occur to anyone that it may be a problem. Too little light, and the plant can’t produce enough sugars for growth. Too much light, and its leaves burn. Most indoor house plants originate from deep forests and jungles, mostly because they survive and thrive in the marginal light found in most houses and offices. However, even they have problems with too little light, which helps explain why the chrysanthemum or Spathophyllum in the back corner of the office hasn’t bloomed once in the five years since it was given as a “Get Well Soon” present.

Unfortunately, with the possible exception of the Australian lance-leafed sundew Drosera adelae, there’s really no such thing as a truly indoor carnivorous plant. Each and every variety requires a tremendous amount of light, in order to expedite growth, digestion, and even coloration. Give a Venus flytrap an insufficient amount of light, and it can’t digest trapped prey, causing the prey to rot and kill the leaf or sometimes the entire plant. Sarracenia pitcher plants, when deprived of light, can’t produce the nectar and coloration necessary to attract wasps and other common prey. Cut the light off enough, and a typical Sarracenia produces purely photosynthetic leaves, called phyllodia, in lieu of traps because getting enough light for survival is more important than snagging the nitrogen and potassium necessary for growth or reproduction. Sundews are even nice enough to let growers know if they’re getting enough light: the mucilage used to snare prey requires a lot of sugars, and that sugar production requires a lot of light. The best gauge of a happy sundew is a sundew covered with plenty of “dew” on its tentacles.

If it’s this easy to make sure that a carnivore gets enough light, then why do so many carnivores die from a lack thereof? I’ve run into so many people that tell me that their plants got “plenty of light” before it died, and they forget one very important fact: their eyes are lying to them.

The human eye is an exquisite sensory organ, the culmination of approximately 600 million years of evolution. It can register a wide range of color wavelengths, it can be used for closeup and long-distance viewing with a minimum amount of adjustment (just try to use a magnifying glass as a telescope in a matter of seconds), and it can adjust to both bright light and near-darkness with equal alacrity. That’s, of course, the problem: because the eye’s evolution was dictated by its need for such rapid adjustment, what seems to be adequate illumination for navigation or even reading isn’t the same as what’s necessary to keep a plant alive.

To demonstrate the deceptive nature of eyeballing light levels, it’s necessary to buy or borrow a standard light meter. This can be a professional photographer’s model, or it can be a horticultural light meter. The horticultural supplier Worm’s Way sells a variety of light meters of varying accuracy, including a solar-powered gauge that retails for about $30 US. I use this model for checking on light levels in my greenhouse, as well as for light levels in windows. It’s not perfect, but it gets the job done.

The first thing to do, after getting the light meter, is to get an idea of its upper range. In most circumstances, the best thing to do is stand outside on a good sunny day and note the reading. Since clouds, haze, dust storms, and obstacles such as trees and buildings interfere with that light, having an idea of the perfect conditions give a baseline for your further tests. By way of example, most carnivores thrive in open spaces such as bogs in areas where scrub and trees are burned off in regular grass fires, and they generally either disappear or go dormant if the scrub becomes too thick to allow sufficient light to hit the bog.

Now that you know what your gauge gives you when exposed to unfiltered and unobstructed daylight, let’s look at the areas where your plants are growing. One of the reasons why standard plate glass is used for windows, other than its cheapness compared to plastic, is because it allows approximately 90 percent of light hitting its surface to pass through without being absorbed or deflected. The polycarbonate used for most greenhouses these days transmits about 80 percent of that light, and it yellows and darkens over the years as it’s exposed to high levels of sunlight, so it’s not as efficient as glass. It gets used, though, because it’s a lot lighter than glass, it’s much less dangerous to move and position, and it’s more likely to absorb or deflect the impact of wayward rocks, baseballs, hailstones, and small firearms without shattering or exploding.

This is also considering that the glass or polycarbonate is clean, new, and unsullied. Experienced greenhouse managers know that too much light can be just as bad as not enough, and Texas gardeners understand that a judicious amount of shade can sometimes be the only thing that gets a collection of plants through the summer. This includes shade cloth being strung over the greenhouse, applying whitewash or thinned latex paint that washes off throughout the growing season, or even planting annual vining plants such as morning glories or moonflowers to provide shade until the first serious frost. Any shading that helps cut the heat in a greenhouse is also going to cut the amount of visible light available to plants inside, so the varieties of carnivore that don’t go dormant in the height of summer, such as most butterworts and bladderworts, may have to be grown indoors if the outside temperatures get above 96° F (34° C) for too much of the growing season.

Okay, you say, you’ll just grow your plants indoors next to windows. It’s time to pull out the light meter again, and measure light both throughout the day and at varying distances from the window. Sure, the light coming through the east window is enough for reading or watching television, but remember that almost all carnivores need the equivalent of full daylight for at least six hours per day, every day. Whip out the light meter and measure the difference between the light available right against the window and the light available at the couch or chair in which you do most of your activities in that particular room. Unless you’re the sort to light everything with multitudes of halogen bulbs, I’d bet that what’s suitable for general indoor human activities is a slow death sentence for your plants.

When we get into indoor lighting, then the light meter gets its greatest workout. Most of the indoor growing guides that recommend that the lights remain only a few centimeters above the growing plants aren’t saying this for grins and giggles, as the light intensity drastically decreases upon distance from the light source. This is why almost nobody recommends using incandescent “grow bulbs” any more, because they throw off so much heat along with their pathetic amounts of visible light that any plant underneath them bakes or parboils at the distance where they receive enough light to make a difference. (To a much lesser extent, this can happen with fluorescent bulbs and tubes, as the ballast throws off enough light that some can be a fire hazard in certain circumstances.) Serious indoor growers use halogen or sodium lamps to supply their plants with suitable light, but those usually come with metal cases with ventilation ducting to vent heat away from the plants. As of this writing, many of those high-intensity halogen or sodium bulbs are being replaced with LED arrays that supply the light without the heat, and for a significant energy savings as well.

When testing indoor lighting, it’s not just enough to test the light intensity at varying distances from the light source, but at varying times. Besides the lack of heat and the lowered electricity costs inherent in using LED lights, LED lighting’s greatest advantage is that the individual light-emitting diodes still produce the same light intensity over years of use. This isn’t true with fluorescent lighting. While standard fluorescent tubes and compact fluorescent bulbs are great for plant lighting, being cheap, energy efficient, and easy to replace, most have an effective lifespan of about eight months to a year. When I say “effective lifespan”, I mean that while the tube or bulb continues to emit light, it’s too low for any plant’s benefit. Unfortunately, as I noted about our eyes’ ability to lie to us, we don’t see the gradual decline, but the light meter never lies.

To give an example, I have to share a story about my good friend Cheryl LeBeau, who lives in Connecticut. She recently started raising American anoles (Anolis carolinensis), which live and thrive in roughly the same conditions as most North American carnivorous plants. One night, she called me asking for serious advice, as her two anoles were dying and a third lizard in the enclosure was not far behind them. I asked about heat and humidity, and she had exquisite control of both. I asked about food and water, and discovered that they were well-fed and well-hydrated, and vitamin and mineral supplements in their water wasn’t making a difference. Cheryl was fond of these lizards, and didn’t want them to die, so I kept asking further questions about their husbandry. Finally, after having eliminated everything else, I asked “What sort of light do you have?”

She related that she was using a fluorescent fixture with a bulb that emitted additional ultraviolet light for reptile health.

“When was the last time you changed the bulb?”

“Oh, about a year ago.”

“That’s your problem.”

“But how could it be the light? The bulb is still working.”

See, Cheryl’s eyes were lying to her, and they were telling her that the light off that old tube was still adequate even as the lizards were telling her it wasn’t. Two days later, she was able to purchase a new tube for her enclosure’s light fixture, and the lizards jumped back to good health so rapidly that she’s still amazed at the difference. She didn’t mean to let things get so far, and she was working with the best tools and information available to her about her lighting. Unfortunately, she wasn’t informed that she needed to change those tubes on an annual basis, and her lizards almost died because nobody thought to inform her until she asked me.

This, incidentally, is why I just replaced all of the lights in my indoor propagation tanks, which use both sunlight from a west window and 20-watt fluorescent tubes. These don’t have to be expensive UVB and UVA tubes designed for reptiles or for saltwater fishtanks: standard tubes sold at hardware and home improvement stores as “plant lights” get the job done, and they can be mixed with the typical cool white tubes to save money. With compact fluorescents, try not to use any bulbs rated higher than 23 watts if they’re going to be used in enclosed areas such as a terrarium because of potential heat buildup. (A handy money-saving tip: considering that full-spectrum CF bulbs are still a bit expensive, they can still be used for standard illumination, such as in hallways or on front porches, long after they’re no longer suitable for plant growth.) Other than that, just measure the light produced by a new bulb or tube with your handy light meter, and check the light every month. When the light produced drops below 50 percent of its original output, switch out bulbs or tubes and notice how rapidly the plants bounce back.

Now, it’s not absolutely necessary to buy a light meter. I’m sure that your eyes are up for noting increases and decreases in ambient light. Considering the cost of your carnivorous plants, though, do you feel particularly lucky?