I am having a little trouble w/potency of my MJ buds… so asked the question on another forum and received this answer:

“Greenhouses filter out UV light. Trichomes, which contain the vast majority of THC, are a defense mechanism against UV.”

So - IF THIS IS TRUE - growing in a greenhouse will not work for cannabis? How can that be? Thanks.


This would be a question for @Cannabian I think he has experience with green houses.


This will be interesting to see what others with experience have to say. I have a greenhouse (not growing weed in it). As I know it, all greenhouse plastic has different ratings when it comes to light transmission. The plastic on my greenhouse has UV treatment but I’m still getting 92% light transmission thru it. It doesnt block it all out. Why I say this is still interesting, I currently have sun gold cherry tomatoes in the green house and the same in the field. The ones in the greenhouse are much smaller than what is in natural light. So this is an interesting topic. Cant wait to here what others say.


I don’t think this is true. Most LED lights don’t include UV in their spectrum. Fact check. @dbrn32. But I wonder if the greenhouse could filter out too much of a more relevant red/deep red spectrum or just block too much overall intensity? Indoor growers would move a light closer to a plant if it’s not intense enough. Since you can’t move the sun, can you raise your plants closer to the top of the greenhouse?

1 Like

Lots of people grow weed in greenhouse with plenty of success, and you can grow plenty potent buds without UV light.

@ccason can you go into detail about your setup? Light intensity, temperature, nutrients, and how you harvest and cure can all have effect on potency of your harvest.


You received bad info. “Greenhouses” aren’t even uniform in material or light reduction. A glass greenhouse might offer almost zero light filtering, while a translucent poly hoop house might offer 30%.

Like @dbrn32 asked, what can you tell us about your personal setup? What greenhouse are you using? Please describe the microclimate temperature and humidity levels.

What genetics are you working with?


I’m not saying you’re wrong about your greenhouse, but I wonder if you aren’t misinterpreting the manufacturer’s info. Greenhouse plastics are almost always UV stabilized, but not UV filtering. The light transmission is a separate rating, and doesn’t necessarily mean it filters all spectrums of light to the same degree. In my experience, double-walled corrugated polycarbonate panels have a wide range of filtering/shade options, while hoop house poly tends to just affect light transmission without much UV filtering.

UV stability just means the plastic won’t become brittle and degrade after a few months of summer sun, which is exactly what happens when you try to use poly tarps meant for painting.

1 Like

I feel like most are designed to withstand degrading from uv light, but they are also pretty widely available with uv inhibitors to block transmission of uv wavelengths.

I have bigger issue with 93% light transmission. It’s probably more like up to 93% light transmission. Even completely clear glass blocks quite a bit of light.


@KeystoneCops I think we are on the same page I just didnt clarify as well as you did. You are correct on the use of the UV treatment keeping the poly from degrading. However with only 92% light transmission I would think something is being lost. Again this is just a guess on my part. I’m not educated enough to have the answer to that. As someone else mentioned, there are plenty of people that have outrageous grows in a greenhouse. I just found the topic interesting because of the difference I see in my tomatoes. The tomatoes were all raised in the greenhouse in the same soil and same feeding schedule. While there is no physical difference in the plants size or health, the fruit is visibly larger on the same plants not in the greenhouse. I have no idea why. Hoping i could learn something from this thread. First time growing in a greenhouse.


I’ve done a hoop house covered in burlap, green plastic and opaque/almost clear. Never glass, one thing I remember from FFA is glass sucks for the same reason glossy paint isn’t good in the grow room. The number one problem I found is heat.

1 Like

some greenhouses are made with the wrong glass. UV treated poly does filter UV rays it is merely more resistant to UV degradation. Your dope may be crappy from a number of things, not the least of which is genetic. Poor soil, not enough sunlight, too cool, too hot, bad watering or feeding practices? But generally weak dope is a genetic thing and phenotype. Terpines are a big part of the user experience, and that is why the other things matter. You can enhance terpine production with proper environmental control, but if it aint there in the first place nothing will help.


yes all of that is correct, there is one advantage poly has over glass, poly can be made diffuse much easier and cheaper than glass. I use diffuse woven greenhouse poly that is wicked durable. In a glass house or regular poly when sunlight is hitting only part of the greehouse the rest is in shade. With diffuse poly it spreads the light very evenly. Way better, Ive tried them both and diffuse wins hands down. Lasts for many years too even in harsh climates.

its cloudy in this shot actually pouring rain


This is the light I have.
It’s a stick built greenhouse. Windows (south) in the front and the rest covered. I use Pure Blend Pro fertilizer. I’m not sure how to attach a picture but I’ll figure it out. Maybe too hot from the south, but not in the winter. North Missouri. I also grow tomatoes and herbs in it.

Sorry - I’m new at this forum. I’ll figure it out and thanks for all the input… I’ve read every one!

Currently I’m on ‘nature’s time’. When daylight is less I use the light.

I use seeds from this site.

Yes I do move the light (posted it below)

FFA Future Farmers of America where kids obtain usable knowledge to apply to growing cannabis. Gotta love it


This is a stick built greenhouse. 10 x 10 built onto my house… south facing windows and all else enclosed. Humidity usually around 40% and I spray them several times a day. Temp - I have heat and a/c in the facility.
Genetics are purchased on this site. Last was Gold Leaf… I’ve had Blue Dream, White Widow, Durbin Poison, Northern Lights…

I don’t have a problem growing I don’t think. It’s the potency that’s lacking. I’m a master gardener, but new to MJ (licensed) I dry it (upside down) then cure in glass canning jars for around 6 weeks with Boveda 62%