Hibiscus sabdariffa var sabdariffa:
"Vernacular names, in addition to roselle, in English-speaking regions are rozelle, sorrel, red sorrel, Jamaica sorrel, Indian sorrel, Guinea sorrel, sour-sour, Queensland jelly plant, jelly okra, lemon bush, and Florida cranberry" (this, from Julia Morton's plant monograph, available through the Purdue University New Crops web site). Seed companies in the United States have also taken to labeling this plant as "Thai Red Roselle." In grocery stores Hibiscus sabdariffa is erroneously marketed as "Hibiscus flowers"; while the pink flowers are gorgeous in their own right, it's actually the fleshy red calyces that are dried for tea and used as food.
When growing hibiscus, climate is definitely a consideration. It's considered a subtropical/tropical plant, so it needs a hot climate to bare usable calyxes and gentle early falls for substantial seed set. The timing of seeding is especially vital for cooler climates. Start seeds early in a greenhouse and transplant immediately after last frost. Here in Ojai (Zone 9B), we start seedlings in April, transplant them by May, get harvestable calyxes by late July, get and herb crop in mid-November.
Seeds can be scarified (we gently brush them with a 150-grit sandpaper) prior to planting to improve germination. It's not necessary but it helps immensely. Amending the soil with copious amounts of potassium (most especially in soils where it is lacking) increases the vigor of the plants tremendously. The Julia Morton monograph referenced above has some anecdotal fertility guidance, suggesting applications of a 4-6-7 NPK.
This plant has an otherworldly appearance and is a real joy to grow. It goes without saying that the homegrown calyces are far superior to anything that can be found in the marketplace, but these seem especially more floral and fruity. Makes a great addition to lemonade or a bioregional substitute for cranberries.
Seeds are certified organic by Oregon Tilth.