I may have recently lucked into a living situation with a large outdoor area with southern exposure that I can use for a small run in a newly legal state. Given that we’re approaching fall and winter, I’m wondering whether it would be possible or advisable to build a small, DIY greenhouse for an outdoor run. The space is in USDA hardiness zone 7b, so it gets down to about freezing, sometimes as low as teens to 20F, but infrequently and not usually for much more than a day or two in the dead of winter.
I’m wondering if anyone has experience with outdoor winter grows and how to do them. I’m wondering about:
What materials I would need to use for the greenhouse? Would plastic sheeting be sufficient, or do I need to use bubble wrap or something for insulation?
How can I heat the greenhouse through the winter? What does heating dictate about the size / scale of the greenhouse?
For photoperiod plants, I assume I would need to veg them indoors and just take them out when I’m ready to flower? Any advice on grow cycle timing?
Thanks man, I didn’t realize PM was associated with short daylight conditions, but that’s good to know. Yes, at the winter solstice, I would be looking at around ~9 hours between sunrise and sunset, and obviously not all of that is going to be direct sunlight. I guess that’s a no go, at least without supplemental lighting?
I’m not sure that it is. But it’s what happened when I tried with short daylight. Maybe it was too drafty for them.
Maybe this winter I’ll try to do some autos by the window and see what happens.
I would be very hesitant to put in the labour of building a greenhouse without at least a little positive reinforcement. Maybe someone else who has done this will chime in.
Well it depends on the size of the greenhouse, the bigger the more costly it is to heat it. There are some types of plastics that have an air gap in them sort of like bubble wrap and better even would be poly sheets or glass. Some operations use gas burners to heat the greenhouse and it helps boost the CO2 leves too. I have seen traditional greenhouse chimneys that use wood, so there are several ways to do it. The greenhouse should be as low as possible to be easier to heat. High ceilings have way more volume which makes them difficult to heat. You can simply extend the photoperiod of the plants and keep them vegging by adding some white fluros or LED tubes or bulbs. They don’t neet much to prevent flowering.
I built this for next to nothing dumpster diving and used wood of OfferUp. I was gonna use a wood burning stove at night. We had temps about like yours in central california. My neighbor was doing it without heat. Humidity You can use clip on lights to prevent plants from flowering but I’d veg inside and put them out to flower.
I have to build another for winter growing in 6b. Usually for winter growing the plastic is installed in 2 layers. They make a very small fan that connects inside and creates an air gap between plastic layers for insulation. Seems there are a few heating ideas already given. If ya got the time and energy maybe look into geothermal. PVC snaked under ground below frost level. The PVC sticks up on opposite ends of the green house. Any inline duct fan can force air through the PVC resulting in warm air from under ground coming out the other end. Lots of up front work getting it installed but can provide decent warmth for the price of running a small fan all winter.
