Recent studies show that hibiscus tea can lower blood pressure as effectively as some standard hypertension drugs can. Hibiscus is widely consumed around the world as a ruby-colored, lemony beverage (it’s the main ingredient in Red Zinger tea). Hibiscus is safe and, unlike most blood pressure drugs, rarely causes side effects. Plus, hibiscus plants can be grown in much of the United States, so you can actually grow your own blood pressure medicine.
Hibiscus (Hibiscus sabdariffa) has been used to treat high blood pressure in both African and Asian traditional medicine. In 1996, researchers in Nigeria confirmed this age-old wisdom by showing that hibiscus flowers reduced blood pressure in laboratory animals. Soon after, researchers in Iran showed the same benefit in people. After measuring the blood pressure of 54 hypertensive adults, the researchers gave them 10 ounces of either black tea or hibiscus tea for 12 days. Average blood pressure decreased slightly in the black tea group, but decreased a significant 10 percent in the hibiscus group.
Since then, several additional studies have confirmed this effect, including two that tested hibiscus head-to-head against standard blood pressure medications:
- Scientists in Mexico gave 75 hypertensive adults either captopril (Capoten; 25 milligrams twice a day) or hibiscus tea (brewed from 10 grams of crushed dried flowers — about 5 teaspoons per 1 to 2 cups water — once a day). After four weeks, the herb had worked as well as the drug, with both groups showing an 11 percent drop in blood pressure.
- In another study, the same researchers gave 193 people either lisinopril, (Zestril, Prinivil; 10 milligrams per day) or hibiscus (250 milligrams in the form of a capsule). After four weeks, the herb had worked almost as well as the drug: Blood pressure decreased 15 percent among those on the drug, and 12 percent among those taking hibiscus.
How does hibiscus lower blood pressure? Recent research suggests a combination of reasons: It has diuretic properties, it opens the arteries, and it appears to act as a natural angiotensin-converting enzyme (ACE) inhibitor, which means it slows the release of hormones that constrict blood vessels. In addition, hibiscus boosts immune function and provides valuable antioxidants.
Dose recommendations vary from about 1 teaspoon of dried “flowers” (technically, the calyxes surrounding the flowers) per cup of boiling water up to the 5 teaspoons used in one of the Mexican studies. Steep five to 10 minutes. If you have high blood pressure, you should own a home blood pressure monitor. Take readings before different doses and retest an hour later to see what works best for you. Check with your doctor prior to taking hibiscus if you’re currently on medication to lower blood pressure — often a combination of an herb and a lower dose of a pharmaceutical provides the same benefit.
As with all medications, allergic reactions or other side effects are possible. If you experience symptoms shortly after ingesting hibiscus, stop taking it until you talk to your doctor.
Grow Your Own Hibiscus
Hibiscus is a perennial tropical plant, so you may think that growing it in the United States would be limited to the Sun Belt and Hawaii. Not so, says Ira Wallace, owner of Southern Exposure Seed Exchange in Mineral, Va. For American growers, Wallace recommends the ‘Thai Red Roselle’ variety of hibiscus, which thrives as an annual as far north as New Jersey.
This beautiful hibiscus has dark green leaves that develop red veins and undersides as they age. The stems and branches are also dark red. Wallace’s plants in Virginia grow to 4 feet high and 3 feet wide.
In temperate zones, this variety of hibiscus should be started in pots at the same time you would start tomatoes. When seedlings are 3 to 4 inches high, transplant them to a sunny spot. Space plants 3 feet apart in rows 5 feet apart. This variety appreciates a soil rich in organic matter, but too much nitrogen will delay flowering until late in the season — possibly too late to harvest many flowers.
At Wallace’s farm in central Virginia, ‘Thai Red Roselle’ begins to flower in late July to mid-August, and continues until frost. She covers plants with row covers during early light frosts, which allows for harvesting well into October.
The flowers are best harvested when fully grown but still tender. They can usually be snapped off by hand, but if stems have hardened, use clippers. Harvesting early and often increases production. On Wallace’s farm, production ranges from 1 to 2 pounds of fresh flowers per plant. It takes 10 to 12 pounds of fresh flowers to make 1 pound of dried flowers for tea. For home gardeners, this means three to six plants should produce half a pound of dried flowers for blood-pressure-lowering tea, and lots of tender young leaves for a delicious addition to salads. Find more hibiscus growing advice from Wallace in How to Grow Hibiscus.