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 this plant, climate is definitely a consideration. Hibiscus sabdariffa is considered a subtropical/tropical plant, so it needs heat to bear usable herbage, but most especially to come to term for seed. Most gardeners in the continental United States will have some success growing the plant as an annual, although it can perennialize in warmer areas. Timing is especially vital for cooler climates. Richo Cech at Horizon Herbs grows the plant up in Southern Oregon (zone 6) and recommends starting seedlings early in a greenhouse and transplanting immediately after last frost. Here in Ojai (Zone 8B), we started seedlings in April, transplanted them by May, and got a seed and herb crop in mid-November.
Seeds must be scarified (we gently brush them with a 150-grit sandpaper) prior to planting. We've found that 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.