Lighting options for indoor orchid growing, both for supplemental seasonal light sources and for year-round growing areas, have evolved in leaps and bounds over the past few years. Indoor horticulture and agriculture are being radically transformed by the availability of high quality light from energy and heat efficient LED grow lights. LED grow lights have evolved beyond simple bulbs into panels and fixtures with a variety of sizes and light intensities.
While indoor grow lights were once ideal primarily for lower light orchid species, such as Phalaenopsis and Paphiopedilum, greater intensity LED grow lights are now widely produced, thanks to the high light demands of commercial cannabis production. We have used high intensity LED grow light fixtures successfully for indoor wintering of high light loving Cymbidium and Australian Dendrobium.
We also have used a second high intensity LED grow light fixture to provide year-round lighting for a 4 ft x 4ft (1.2m x 1.2m) humid, cool-growing area. An unforeseen problem? The canes on our Dendrobium subclausum grew so large, it expanded horizontally and vertically out of the 4ft (1.2m) space. The outside of the plastic basket is being obscured by root growth. LED grow lights work for orchids!
“Hitting the heat wall” with T5 HO fluorescent grow lights
One of our recent ventures in orchid culture was to create a dedicated “warm room” for a seedling growing area, to maintain higher humidity and 62F+ (17C) night temperatures for recently deflasked orchids. The growing area worked so well that we moved another shelving unit, with blooming size and near bloom size Paphiopedilum, and a few Phalaenopsis and warmer growing Dendrobium species, into the nursery room.
All of these shelves were originally illuminated with T5 HO fluorescent grow lights, using either Sun Blaster or Hydrofarm Agrobrite fixtures. Full spectrum T5 HO lighting worked well, with good root growth and consistent flowering (9-10 hrs/day of light). However, we began to encounter something common in many vertical growing setups: too much heat building up in the room.
Even in relatively cool central California, the heat output from the fluorescent lights began raising the orchid room temperature into the upper 80s F (30C) in early autumn. Earlier in the summer, it was not so much of a problem: when the rest of our house reached 80F (27C), the air conditioning would automatically turn on, effectively capping the heat build up in the growing room. But as the rest of the house stayed cooler, due to lower daytime outdoor temperatures, the AC didn’t run, and heat continued to build in the warm growing room.
The new option: T5 HO LED grow lights
What to do? I wanted to bring the heat output (and electricity usage) down to the level prior to adding the additional shelves. However, we had perfectly good T5 HO fixtures. What did I discover? A few companies have identified this market, for all of us (not just orchid growers) who have invested in extensive T5 fluorescent lighting over the years. There are LED grow light “bulbs” designed to fit into T5 HO lighting fixtures! Some of these T5 HO LED replacement bulbs use nearly half of the electricity, with a comparable reduction in heat output.
T5 HO LED replacement “bulbs” are actually a LED strip inside of a polycarbonate or glass tube with the appropriate electrical connection at the end to fit into a T5 fluorescent fixture. These are designed to last 30,000-50,000 hours, depending upon the manufacturer. That translates into about 8-10 years of daily usage.
While evaluating the longevity of T5 LED replacement bulbs, I noted in one brand’s technical specifications that they are NOT expected to simply “burn out” at the end of 30,000 hours, but might decrease to less than 90% light output after that time. No one has had that length of experience with new LED horticultural lighting technology, so we will see how long LED strips actually remain useful. I expect in coming years that lighting technology will have advanced so much that maximum longevity will be irrelevant; there will be better, cheaper, and hopefully even more energy efficient options available for replacement.
It just smelled awful and no fire occurred
At the time of beginning my research (September 2018), there were six companies to consider for T5 HO LED grow light replacements. Now, over a year later, there are even more options.
Before you excitedly purchase the least expensive T5 HO LED replacement bulb and pop it into your existing fixture, I would like to explain some significant details that generally do not show up in bold print on a product page. Based upon our experience with our first set of T5 HO LED replacement bulbs, one company’s product was removed from sale for awhile.
Oh yes, I never realized that buying orchid grow lights could get this exciting. In summary: it just smelled awful on a Sunday morning and no fire, or harm to the orchids, occurred.
Here’s the situation. Not all ballasts in T5 lighting fixtures will work with all T5 HO LED replacement bulbs. (The ballast is behind the fixture reflector and responsible for regulating the current, and providing sufficient start-up voltage, to the bulbs.)
Manufacturers do not comprehensively test all ballasts. In our case, I figured that we were okay since we use Hydrofarm Agrobrite and Sun Blaster fixtures — widely used manufacturers for T5 HO fluorescent horticultural lighting. I assumed that, if the T5 HO LED replacement bulbs did not work in those fixtures, the manufacturer would not have much of a market.
Well, I was wrong. The first local manufacturer that we selected for trial, Waveform Lighting, had apparently re-marketed their residential/commercial T5 full spectrum LED lights for horticultural applications. After describing my experience with their smoldering PhotonTube T5 LED bulb, it was determined that there was likely a problem with using the product in a T5 HO (54W) ballast. They only tested regular T5 (28W) fixtures. Waveform promptly refunded all of our money, sent a return shipping label, and immediately removed these T5 LED replacement tubes from their website pending further testing.
As of late 2019, the PhotonTube is back on the market, with a listing of compatible ballasts in a pdf downloadable from the product page. However, the main product description still exhorts “plug and play” into your existing T5 ballast. As we demonstrated, buyer beware with any T5 HO LED replacement bulb making such claims.
(Note: we do not receive compensation from any manufacturer, or any free products. We’ve trialed many horticultural lights, and would like to help other orchid growers with our experience.)
T5 HO replacement LED grow lights: ballast compatibility
After the failure of the Waveform Lighting product, and considering several other manufacturers (e.g., Gardener’s Supply Company, Thrive AgriTech, AgroLED), I selected Active Grow Horticultural Lighting for our next set of T5 HO replacement bulbs. When I first purchased these T5 HO LED grow lights, they were anticipated to work with both Hydrofarm Agrobrite and Sun Blaster Fulham ballasts. They performed beautifully in our Agrobrite fixtures so I ordered a second set to replace the fluorescent tubes in one of our Sun Blaster fixtures.
Alas, it turns out that the lights were compatible with Sun Blaze fixtures, not Sun Blaster. The replacement LED grow lights seemed fine at first, but began to flicker after 20 minutes. While manufacturers list the ballasts that they have tested, there were no obvious labels on our original T5 HO fixtures from Gardener’s Supply Company — just a sticker with “Sun Blaster” on it.
It is possible to unscrew the metal reflector on some T5 HO fixtures to look at the interior electrical components. You should be able to see the ballast, and read the “fine print” of the specific ballast manufacturer and model. This is important “fine print” if you wish to be sure of a compatible bulb purchase! And avoid the meltdown that we experienced in our unaware initial trial.
Sun Blaster initially planned a product launch of their own T5 HO LED replacement bulbs in early 2019. However, the bulbs never became available and were removed from their website. (Earlier versions of this article did contain specifications on those bulbs and a comparison with other available bulbs. I removed that content to avoid confusion and obsolete product information.)
Energy usage: ballasts and wattage
With this information, I realized that we were at a crossroads: continue using our existing T5 HO Sun Blaster fixtures, or convert the lighting to an entirely new LED grow light fixture. Again, the LED light learning curve stepped up a notch to understand product options — and energy usage — more thoroughly.
When you buy a replacement T5 HO bulb at a given wattage, say 24W, and plug it into a T5 ballast, you likely add 4-6W per bulb of operating electricity usage. In other words, each bulb now actually uses 28-30W of electricity. You can expect a T5 HO LED replacement fixture with two 24W bulbs to operate at 60W. That can be significant with many bulbs in use: about 25% more electricity usage than you might initially anticipate from your LED conversion.
Grow light manufacturers tend not to prominently point this out for replacement bulbs. But the full electricity consumption, including the ballast, should be included when there is a specification for an entire light fixture (LED or fluorescent).
More options: evolving beyond the ballast
T5 HO light fixtures with ballasts are a technological carryover from fluorescent lighting. LED light fixture design is advancing towards non-ballasted fixtures, but these are not yet developed for T5 HO LED bulbs. However, Active Grow has developed two ballast-free LED light fixtures: one with replaceable T8 bulbs and another with non-replaceable LED “bulbs” (strips) integrated into the fixture. The light intensity (output) of these is less than a T5 HO LED fixture … but so is the electricity usage because there’s no power consumption by a ballast.
Yes, it gets a bit complicated when you delve into the details.
For comparison, a 4′ ballasted fixture with two T5 HO LED replacement bulbs will use 60W of electricity (with 24W bulbs). The 4′ non-ballasted two bulb fixture from Active Grow, called the Propagation Luminaire, consumes 40W. The non-ballasted 4′ four bulb T8 fixture from Active Grow uses 88W of electricity.
Additionally, there are LED strip lights manufactured by Sun Blaster in a variety of lengths. A Sun Blaster LED strip delivers 25% more lumens for the same wattage compared to a Hydrofarm Agrobrite T5 HO fluorescent tube. These LED strips are thin and lightweight compared to heavy metal T5 fixtures. However, the energy savings relative to a fluorescent tube is minimal: a 4′ Sun Blaster LED strip is 48W, only 6W less than a standard 4′ T5 HO fluorescent tube.
What did we do with all of these choices?
Ultimately, we decided to convert our three tier seedling shelves to the Active Grow 40W LED light fixtures. The seedlings would not benefit from the higher light intensity of the T5 HO LED replacement bulbs, and 33% energy/heat savings (40W vs. 60W) is very notable. Also, I did not want to invest in LED grow lights that did not truly meet our growing needs just to keep the older technology of our T5 HO ballasts in service longer.
For our other LED grow lights, we opted to use T5 HO LED replacement bulbs. I had existing compatible fixtures for some, and purchased new fixtures for two other shelves. After a year of trial, I also decided to swap out our 400W Amare Technology high intensity LED fixtures for 240W fixtures with eight T5 HO LED replaceable bulbs from Active Grow.
Finally, we use a few Sun Blaster LED strips for supplemental afternoon lighting in our eastern windows. I am satisfied with these unobtrusive lights overall, but the spectrum is distinctly more “blue” than the Active Grow LED light spectrum. It is not noticeable with ambient natural light, but less visually pleasing as a sole light source. This observation brings us to our next important topic: the light spectrum of LED grow lights compared to fluorescent bulbs.
T5 HO LED grow lights: light spectrum
When switching from fluorescent lights to LED grow lights, you will likely experience a notable difference in the “color” of the LED light — and, hence, your orchids.
For example, the visual light quality for the Active Grow LEDs appears more “yellow” compared to the Agrobrite and Sun Blaster T5 HO fluorescent bulbs that I have used (see photo). This is due to the greater emphasis on the “red” end of the visible light spectrum compared to the “blue” wavelengths. It is an easily overlooked point, but you might want to choose one LED manufacturer (and hence light spectrum) for your fixtures if you wish to have color uniformity in your growing area.
I would say that the Active Grow LED lights appear more “natural” and visually pleasing compared to any of our T5 HO fluorescent tubes. This is what you would expect: this manufacturer’s “Sun White” LED spectrum has a much higher CRI (color rendering index) than fluorescent lights.
Ultimately, it’s not what I “see” that matters, but how the plants respond to available photosynthetic wavelengths. Based upon the quality of light spectrum (photosynthetically active radiation, PAR) and efficient production of photosynthetically valuable wavelengths (photosynthetic photon flux density, PPFD), LED grow lights are a resounding upgrade from our T5 HO fluorescent lights.
The light spectrum is at the heart of any grow light’s value, and LED technology brings the potential for an “indoor sun” like never before. However, a second “buyer beware” caution is in order. It is easier to copy spectrographs and product information than it is to actually build a high quality LED grow light which genuinely performs according to its marketing material. While there are many bona fide quality manufacturers, there are also “cheaper” LED grow lights of questionable spectral output, technology, and longevity.
For more detailed discussion of how LED grow light spectra compare to fluorescent tubes, and important technical specifications to consider, please see my article on “New ways to think about indoor orchid growing with LED grow lights.”
Orchid growing with LED lights: results
After a growing season using our new LED fixtures, I am very pleased. In addition to less electricity usage and heat emission, I am observing equal to better growth and flowering. Most of the species that we grow — even higher light Dendrobium — did not need the greater intensity light provided by the 400W LED fixtures that we initially purchased. Remember the Dendrobium subclausum that I mentioned in the introduction? This vigorous, high light orchid is growing better, and has bloomed more profusely, in a new growing area with 120W LED strip lighting than when residing under the 400W high intensity LED fixture.
Thus, more light is not always better — or needed. This is an important aspect of selecting the right LED fixture for the orchids that you are growing. Additionally, orchid placement (distance from the lights) is a critical, and often ongoing, adjustment until you “get it right” for a particular orchid.
Currently, we are flowering most of our indoor orchids (Paphiopedilum, Dendrobium, Leptotes, Epidendrum, Sarcochilus, Vanda falcata) at 7.5-9 hours/day of light. It might seem surprising that such a diversity of genera receive the same hours of LED light per day. Rather than changing the number of hours of light, I modulate light intensity needs by the number of bulbs, and plant distance from the light fixture. For example, small mottled leaf Paphiopedilum grow about 13″ (33cm) below two 4′ T5 HO LED bulbs (4’x2′, 1.2m x 0.6m shelf) while the same size shelf with moderate light Dendrobium uses four T5 HO LED bulbs. Our cool-growing area (4’x4′, 1.2.m x 1.2m) has eight 4′ T5 HO LED bulbs, and orchids placed from 10″/25cm (Mexican Laelia) to 40″/1m (Sarcochilus, Vanda falcata) below the fixture.
While I do not have personal experience growing blooming-size Cattleya under lights, one reviewer of Active Grow T5 HO LED grow lights indicated excellent flowering results with 16 hours/day of lighting.
I observed two immediate differences in the warm growing room with the conversion of the T5 HO fluorescent bulbs to LED light fixtures: lower room temperature and less rapid drying of the small (2″/5cm) seedling pots. With a year of growth now complete, I can report that both seedlings and blooming-size plants have thrived. Observing a lightly “bleached” appearance to a few species’ leaves, I decided to move some lower light Paphiopedilum seedlings to a new shelf with another 40W Active Grow LED fixture hanging higher (18″/46cm) above the plants than the other shelves (13″/33cm).
Final reflections on LED grow lights for orchids
I hope that our journey into the world of T5 HO LED replacement bulbs for orchid growing provides a good starting point to consider your options. First key lesson learned: do not assume that your existing T5 HO ballast will work with any T5 LED replacement bulb. Second, when comparing manufacturers, light quality (spectrum) is as important as quantity (output). Third, investigate both ballasted and non-ballasted lighting options for electricity usage; it might be worthwhile to replace your T5 HO fixtures with newer technology in some situations. And, of course, consider that a cheaper product is not always better for long term energy consumption or growing results.
As a final reflection, I certainly would not purchase another T5 HO fluorescent fixture, though I am pleased to have T5 HO LED replacement bulbs as an option to extend the life of our existing fixtures. Instead, for my new growing area innovations, I would select a non-ballasted LED grow light or T5/T8 HO LED fixture with replaceable bulbs. The decision would depend upon the 1) light intensity desired, 2) whether it was a supplemental or primary light source, and 3) size of space to illuminate.
Happy orchid growing with bright and beautiful LED lighting!