What kind of hibiscus is it? Most recipes cite H. sabdariffa, but this plant is uncommon and in my experience hard to grow.
More commonly available is H. rosa-sinensis, which is the common tropical hibiscus. I have made many batches of wine with H rosa-sinensis. I remove the entire pistil, then dry the flowers. Then I put them in a ziplock in the freezer until I have enough. Don't worry if the flowers brown a little, the color is still there. Just watch for mold. If you collect them when it is dry you should be fine.
I find it easier to count flowers than to weigh them. This allows you to use the same number of flowers whether they are dried or not. 80 flowers per ounce is my rule. I find 160 flowers/gallon to make the wine a little too thick, so I've cut back to 120-140 flowers per gallon.
Most recipes have you pour boiling water over the flowers, then remove the flowers when cool. Don't leave the flowers in this step too long. Hibiscus flowers have a lot of mucilage
. This is a polysaccharide which means two thing for the wine. First, it is fermentable, which means that after the sugar is fermented you get this extended sort of secondary fermentation which can last for weeks. It looks a little like MLF. Second, it can make the wine almost syrupy in thickness. Think "body" but in the extreme. So follow the recipe carefully, don't squeeze the bag too hard, and don't overdo the flowers.
Hibiscus in my opinion benefits from a second element for flavor. I've used citrus, ginger, grape concentrate, and the leftover cake from a pressed fruit wine such as blueberry. My favorite hibiscus wines is Costa Rican Hibiscus, the recipe is here
. You will have to clarify it, but it is really an interesting, wonderful wine.