UV lighting and orchid fragrance.
Hey folks, so I want to bring up a little something that I have discovered in my grow enclosure. I am finding that UV radiation enhances or enables fragrance of orchids.
For background I grow in an enclosed grow tent. I use two lights, a mars hydro sp 150 and sp 250. The SP 250 did originally have UV diodes. These lasted for about 2 years and have sense died. During this period of time I had lovely fragrances from my orchids. The past few years however I have noticed a dwindling or non existent fragrance from orchids that normally or have been fragrant in the past.
This past week I decided to bring a few plants outside while my area had sunlight and non freezing temps. I brought out a Trichoglottis triflora. This plant has always been powerfully fragrant even with its small size. Its current blooming had been open for about 2 weeks with zero smell. With in 3 minutes of direct sunlight, it regained its fragrance and it lasted for a few hours after being replaced in my grow tent.
I recently added into my tent a 5.0 UVA/B reptile bulb. This is indented for tropical reptiles and amphibians. I have it placed near the center of my tent, and well beyond its recommended usage distance. I have had some interesting results.
I have a Den. spectabile (hoosier x shorty) that has bloomed for me in the past with zero fragrance. I had the light on for three hours the first day, and when I stuffed my nose into the flowers I was surprised. They actually smelled fantastic. It wasnt strong, but I dont have a basis to judge its fragrance on.
In the past I have had plants like stanhopea, that were not in the direct path of the light with UV that remained powerfully fragrant.
Over the last few days I have increased the timer on the light to about 9 hours or so. And I have consistent fragrance from both plants.
With that being said, there are still a wide variety of conditions I think left out in play, temperature being a big one. I grow on the cold side.
Last year I did have two separate Laelia anceps vars bloom, both smelled of cinnamon but was very underwhelming. I plan to see if these lights do anything for them next winter.
The light it self is fairly low wattage, in the teens, and is at least 3' from any plant. I am a bit hesitant to start blasting UV radiation on my plants when they have had zero exposure to it. Wary of burning. However I do think that I will upgrade the 5.0 bulb to a "desert" oriented bulb, 10.0, in time and see if the increased UV light changes the intensity of the fragrances.
I have read some journal/online entries that claim some species or genera do need UV radiation for specific pheromone production. That has me asking, is that what we actually smell? or is what we smell something entirely different than what deceptive orchids use to attract a pollinator.
Does anyone else that grows entirely closed off from sunlight have any experiences with orchids loosing fragrance or not having any when they should? Another possibility is that my lights don't have a great UV spectrum. But this then asks the question is it the UV radiation or the wavelength that makes a difference? I have zero idea. I have a very limited test group, I dont believe I grow many fragrant plants. But it would be nice to enjoy the ones that are.
Edit: Not sure if possible but I think I should have posted this to the advanced discussion. Could a mod potentially move it over?
Last edited by Green Mage Orchids; 03-27-2023 at 11:28 PM..
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