Well, here in Kalifornia we have an extended season. I’m planning on fitting one of the garden boxes with a retractable plastic greenhouse frame - It’ll be interesting to see how it works out.
There are 4 or 5 growing zones in Kalifornia, depending on temps and altitude.
Whereabouts are you within 200 miles ?
What are you planning on Fall planting with the retractable greenhouse ?
Is the retractable greenhouse for starting seedlings , or for growing fully developed plants ?