But you can order dried flowers of Hibiscus, and in that case, use only 8 oz of dried hibiscus flowers.
Here's some of the online sources:
http://www.oldtimeherbs.com
https://www.surfasonline.com/products/31499.cfm
If you use dried hibiscus, it would be interesting to add 4 oz of dried elderberries also, and make sure to pour boiling water over the dried hibiscus and dried elderberries, about 1 quart and steep for 4 hours at least. Also double the amount of yeast nutrient and add 1 tsp magnesium sulfate.
About my wines: I don't want to see my fruits wasted so the excess becomes wine. With 275 kinds of fruiting plants, I managed to make 48 kinds of wine last year that are mainly from my excess production. I also have a very good recipe for coffee wine that rivals Kahlua minus the very sweet part.
Been making wine for about 30 years todate.
Joe