© Dinesh Valke · CC BY-SA 2.0 · Commons
Roselle
CautionRoselle (Hibiskus) · (Hibiscus sabdariffa)
Mallow family (Malvaceae)
Description
Roselle is an annual mallow plant from the tropics, growing one to three metres tall. What sits in the cup as a "hibiscus flower" is not the flower at all: it is the fleshy, deep-red calyces, which close around the seed capsule after the petals drop and are harvested at that point. Their colour comes from anthocyanins, their sourness from citric, malic and hibiscus acid, alongside vitamin C and mucilage. The infusion is drunk all over the world under its own names — karkade in Egypt, bissap in West Africa, agua de Jamaica in Mexico — hot as well as cold. In shops the goods are often labelled simply "hibiscus" without naming the species; for tea it means Hibiscus sabdariffa, not the ornamental hibiscus from the flowerpot. In clinical trials the infusion showed a mild blood-pressure-lowering effect. Anyone on antihypertensive medication should know this, because the effects can add up.
CONTRAINDICATED during pregnancy
Not recommended. Animal studies suggest a possible risk and sound human data are lacking. This applies to regular tea consumption as well as to supplements.
The dried calyces are traditionally used to make a tart red tea, drunk worldwide as a refreshing beverage. Prepared cold it tastes milder, because less tannin dissolves.
Preparation & dosage
Pour 250 ml of boiling water over one to two teaspoons of dried calyces and steep for five to ten minutes. For a cold brew, leave the same amount in cold water overnight.
- Doses per day
- 3×
Sources: [3]
A pooled analysis of 17 randomized trials found a reduction of systolic (upper) blood pressure by an average of 7.1 mmHg; for the lower value and for blood glucose the difference was not significant. LDL cholesterol showed a small drop of 6.8 mg/dl. Doses ranged from 15 mg to 9 g daily, as capsules or as tea, over 15 to 90 days. The authors note a moderate risk of bias, widely varying preparations and studies that were too small — they call for longer and better controlled trials. The tea does not replace treatment.
Sources: [1]
In hot countries the chilled infusion counts as a thirst-quencher and is traditionally valued for its vitamin C content. Some of the vitamin is lost when brewing with boiling water — a cold brew keeps more of it.
Sources: [3]
May lower blood pressure and interact with antihypertensive drugs (e.g. ACE inhibitors); caution also with diabetes medication, as blood sugar may be affected. Not recommended during pregnancy and breastfeeding, as safety is not established and animal data suggest a possible risk. If you take medication or have a condition, consult a doctor before regular consumption. The infusion is distinctly acidic — drunk frequently across the day it can attack tooth enamel; rinsing with water afterwards helps.
Not recommended. Animal studies suggest a possible risk and sound human data are lacking. This applies to regular tea consumption as well as to supplements.
No sound data on breastfeeding are available. Without such data, regular consumption is inadvisable.
Customary as an occasional drink. Because of the blood-pressure-lowering effect and the acidity, daily consumption in larger amounts is not appropriate for small children.
Drug interactions
Blutdrucksenker (ACE-Hemmer, Diuretika, Sartane)
In trials hibiscus lowered upper blood pressure by an average of 7 mmHg. Together with ongoing treatment the effects can add up and drive pressure too low.
Blutzuckersenkende Mittel
An influence on blood glucose is described but was not significant in the pooled analysis. Still worth keeping an eye on during diabetes treatment.
Hydrochlorothiazid und Diclofenac
Altered excretion or absorption under hibiscus has been described for these two agents. Mention regular consumption to your doctor.
Contraindications
- Pregnancy and breastfeeding.
- Low blood pressure — the infusion can lower it further.
Harvested part: Calyces
- Time of day:
- About two to three weeks after flowering, when the calyces are plump and deep red but the seed capsule inside has not yet split. Later they turn woody.
- Drying:
- Remove the capsule and dry the calyces in the shade or at no more than 40 °C. Sun bleaches the anthocyanins — properly dried material is deep red, not brownish.
- Storage:
- 12 months — Airtight and dark. The calyces attract moisture and then clump together; a desiccant in the jar helps.
- Anthocyane (Delphinidin-/Cyanidin-Sambubioside)FlavonoidFlower
The pigments of the calyces; sensitive to light and prolonged heat.
- Organische Säuren (Zitronen-, Hibiskus-, Apfel-, Weinsäure)OtherFlower
Make up roughly 15–30 % of the dry matter and give the infusion its sourness.
- Vitamin CVitaminFlower
- Schleimstoffe (Polysaccharide)MucilageFlower
- Polyphenole und GerbstoffeTanninFlower
- Mineralstoffe (Kalium, Calcium, Eisen)MineralFlower
- [1]MonographEffects of Hibiscus sabdariffa on blood pressure and cardiometabolic markers: systematic review and meta-analysis (Nutrition Reviews 2022, PMC9086798)(accessed: 2026-08-20)
- [2]MonographHibiscus Sabdariffa: Uses, Side Effects, Interactions (WebMD)(accessed: 2026-06-23)
- [3]MonographEgyptian Herbal Monograph: Hibiscus sabdariffa L. (Egyptian Drug Authority)(accessed: 2026-06-23)
- [4]CommonsFile:Hibiscus sabdariffa (6309645399).jpg — Wikimedia Commons(accessed: 2026-06-23)