I haven't tried hibiscus mead yet, but it makes a good wine. I buy my hibiscus from whole foods in bulk it is about $18 a pound. My recipe is for 3 gallons 1/2 pound hibiscus flowers, 6 pounds sugar, two tablespoons acid blend, two tablespoons yeast nutrients, and one packet red star champagne yeast.
Start by bringing two gallons of water to a boil and adding the hibiscus turn the heat of at addition. In another pot invert the sugar by heating it to 250 degrees F with just enought water to liquefy and the acid blend. Once the temp hits 250 add the yeast nutrients and turn of the heat and cover for ten minutes. Next strain the hibiscus water into the pot that has the sugar in it and let it cool. Then mix it and pour all into a 3 gal carboy to off to 3-gallon mark and add you rehydrated yeast.
Rack at 1 month then bottle when clear. Age one year for best flavor.