Use My Greenhouse For Overwintering

Question

Hi there – I am in Zone 4 (west-central Wisconsin) and I built a small greenhouse using a plastic shelving unit and greenhouse plastic, alot of duct tape and velcro. I added screened vents and a door that can be left open (rolled up) or closed with velcro, it seals up pretty tight. I have a lemon verbena and canna lilies I’d like to try and overwinter in there but I would like some advice. When the door is closed up, it gets very warm, it faces the east and receives morning and afternoon light. I built it with the intention of starting plants next spring, which I have grow lights and heat pads but after learning how warm it gets in there I don’t know if I will need them. Any advice on overwintering plants and using the green house for a starting plants will be very helpful. I have attached a photo, thank you in advance for your help.

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Answer 1

I don't think it has enough protection/heat for the coldest nights in Wisconsin for overwintering tropicals like canna lilies, which can be overwintered as a rhizome. The lemon verbena is hardy to zones 9 and 10, so it, too, probably would not survive winter in this greenhouse. Starting seeds after the worst of winter has passed should work. Here is more on low-cost hobby greenhouses and hoop houses:

https://www.gardeningknowhow.com/special/greenhouses/diy-greenhouse

https://extension.uga.edu/publications/detail.html?number=B910&title=hobby-greenhouses#title1

https://www.gardeningknowhow.com/garden-how-to/info/diy-hoop-house-ideas

https://www.gardeningknowhow.com/featuring/learn-how-to-extend-your-growing-season-gardening-beyond-the-spring-and-summer