AZ Winter Greenhouse Grow

Hey Friends! Anybody else here in the PHX AZ area, or in a similarly hot desert climate? Now that Arizona has legalized home grows, I’m considering putting a 6x8 Harbor Freight greenhouse in my sunny, walled-in backyard and putting a few plants in there for a winter grow.

I would start them indoors under LEDs very soon and then move 'em outside around January 15th, once they’ve had about 6-8 weeks to veg and are showing sex. I’m planning to do 8-week flower strains, which would put harvest just before the spring equinox, if all goes to plan. I’m thinking 25 gallon grow bags would cover my needs for this sort of grow, or maybe in 15's?

Has anybody else tried a winter greenhouse grow in a similar climate? Long term forecast is showing the coldest nights reaching 42° in January, but of course that could change. We’ll have about 10.5 hours of daylight at that point in January, and they will get full sun much of the day, but the solar angle is somewhat low that time of year at 33° north latitude.
Essentially wondering if this is a doable proposition and worth the investment. With a barebones setup I could accomplish this for about $500–600 (greenhouse, cinder block + lumber foundation, smart pots, soil, I have a wall mount osc. fan already) The goal would be to provide for myself, friends and family, ideally for much of the spring and summer.

Thanks in advance for any advice, fellow desert dwellers

Your plants will likely reveg putting them outside after the winter solstice when the day lengths begin to increase. They will flower initially when you put them outside due to the the decrease of light hours going from indoors to out, and then will likely begin to reveg once they notice the increasing day lengths.

I ran light dep greenhouses for years and plants definitely notice increasing/decreasing day lengths. Just because a plant is receiving less than or more than 12 hours of light is not concretely indicative that it will flower/veg. The latest I could get away with a flower cycle was starting flower late Oct. to finish late Dec. I’m in CA.

Interesting, I definitely wondered about that, but I figured I'd be safe before the equinox. I could run a small light in January and February to keep it at an even 12 throughout the winter I guess. Definitely not pulling tarps all Feb and March tho

Would be curious to hear any other input on that aspect. I could have sworn I've seen Cali growers doing greenhouse grows and flowering into early April without revegging, but it definitely depends on latitude and strain. Thanks for the input

vtguitar88 said:

Interesting, I definitely wondered about that, but I figured I'd be safe before the equinox. I could run a small light in January and February to keep it at an even 12 throughout the winter I guess. Definitely not pulling tarps all Feb and March tho

Would be curious to hear any other input on that aspect. I could have sworn I've seen Cali growers doing greenhouse grows and flowering into early April without revegging, but it definitely depends on latitude and strain. Thanks for the input

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If it was strictly dependent on the 12hrs then all outdoor plants would begin flowering during the autumnal equinox (Sep. 22). This is not the case though, I've had plants begin flowering in july when the days are still ~14hrs.

The grows you saw could of been deps. I ran deps to flower year round but it was a PITA because I had to manually pull tarps at the exact same time everyday. Having an automated light dep greenhouse would be great but they cost big bucks.

When I would veg I had lights that would come on for an hour in the middle of the night. Similar to the gas lantern routine some people run indoors. Breaking up the dark cycle with only an hour of light interrupts the plants flowering hormone.

Yea the auto light dep greenhouse has been my dream setup for a while now. Definitely not going for anything that serious at this point in my life. Strictly a hobbyist for now.
The conversation I’m referencing definitely wasn’t about light dep though; or else they wouldn’t have been discussing the latest point in the spring where they avoid reveg. How far north are you in California? I’m at 33° latitude here so equivalent to between LA and San Diego. Further north the changes in day length would be notably more drastic, which I’d imagine would be more likely to trigger reveg even at under 12 hours daylight. As you say though, even for full season plants this is entirely strain and even pheno-dependent. I’ve had plants start flowering in northern New England with 14+-hr days in July, and others that don’t show any pistils till September. Which is a nightmare when frosts usually come shorty after fall equinox

FWIW I just compared the changes in day length of my current locationwith those of the area I’ve grown (and lived) previously, in far northern New England.

Phoenix, AZ Day Lengths
Jan 15: 10h 10m. Mar 15: 11h 57m.
Diff: 1h 47m

Burlington, VT Day Lengths:
Jan 15: 9h 10m. Mar 15: 11h 53m.
Diff: 2h 43m

Burlington is at about the same latitude as Eugene, OR (~44N). Phoenix is at 33N. Pretty huge difference in seasonal lighting change between the two locations. I’m a nerd so this was for my own edification but figured I would share since it may affect the outcome of a winter flowering period