In herbal parlance, hawthorn is known as a tonic. Tonic herbs typically strengthen and normalize function and, depending on the problem, they have different actions in the body.

In the case of congestive heart failure, hawthorn helps make the heart muscle contract more forcefully and pump more blood. If your heart beats erratically or too fast but medication is not yet required, hawthorn can help restore your heartbeat to normal and might keep the condition from getting worse.

Hawthorn is a potent antioxidant that scavenges free radicals, the free-roaming, unstable molecules that damage cells and cause premature aging. It also protects and regulates collagen, a fibrous protein that is essential for healthy tendons, ligaments, and other connective tissues in the body, says Pamela Herring, N.D., a naturopathic doctor at the Naturopathic Clinic of Concord in New Hampshire.

Any type of inflammation destroys collagen, so hawthorn can be a good treatment for people with an inflammatory disease like arthritis, she says. "I recommend hawthorn to a lot of patients who are getting up in years and have heart problems and arthritis. It’s an herb that addresses all of these conditions."

The genus name, Crataegus, refers to the plant’s hard wood and sharp thorns. Hawthorn can be termed either a small tree or a large shrub because it can reach 30 feet in height. Many people commonly called the plant haw.

Haw’s healing properties were known as far back as the first century a.d. In the sixteenth century, it shows up in herbalists’ texts as a remedy to stem the flow of blood, because the berries were so astringent. It apparently wasn’t widely used for heart problems until the beginning of the twentieth century, when some American drug companies began manufacturing a hawthorn extract as a cardiac tonic. Some American physicians still prescribed the extract in the 1940s to treat high blood pressure.

Herbalists long considered the berries the medicinal part of the plant, but the flowers and leaves also contain active ingredients. As with most herbs, hawthorn probably has several active ingredients that work in harmony.

Some of the more important ingredients include a mixture of pigment chemicals known as flavonoids. These compounds give the hawthorn berry its distinctive reddish blue color. Flavonoids scavenge free radicals and lessen the bad effects of inflammation. They also seem to reduce cholesterol in the bloodstream.

Proanthocyanidins, another large group of chemicals, seem to be largely responsible for its beneficial actions on the heart. These chemicals relax smooth muscles in blood vessels so they won’t suddenly constrict and shut off blood flow, which can happen when emotional and physical stress taxes the heart muscle so it demands more blood and oxygen.

When ancient physicians used hawthorn as a heart herb, they usually were treating congestive heart failure, which they loosely termed dropsy. Dropsy actually describes the symptoms of edema, an accumulation of fluid in the tissues. When the heart is weak and can’t pump enough blood, fluid often accumulates around the ankles. Because hawthorn works as a mild diuretic and purges excess fluid from the tissues, it gives relief from this symptom of heart failure.

Hawthorn also has an extraordinary effect on the heart itself. In some cases, it improves the heart’s mechanical pumping action and increases the force of its contractions, says Eran Ben-Arye, M.D., a researcher at the national medicine research unit at Hadassah University Hospital in Jerusalem.

In some cases of congestive heart failure, hawthorn seems to work well. In a German study, researchers studied 78 patients between the ages of 45 and 73 who had mild to moderate congestive heart failure. Over an eight-week period, some of the patients received 600 milligrams of hawthorn extract daily, while others were given a liquid that looked and tasted the same but contained no hawthorn (a placebo). During the study, patients were not allowed to take any other types of heart medication except diuretics. Their fitness levels were measured using a type of stationary bicycle.

At the end of the study, those treated with hawthorn significantly improved their performance on the bicycle. They also had lower systolic blood pressures (the upper number in a blood pressure reading) and lower heart rates, both of which indicate improved pumping action.

"It was a good, well-controlled study with results that seemed to reinforce the folk use of the herb," says Dr. Ben-Arye. "In the case of mild congestive heart failure, I think hawthorn may be an efficient medication."

In more advanced cases, hawthorn can be used in combination with digitalis or other herbs and medicines containing compounds called cardiac glycosides. Studies show that hawthorn appears to enhance the action of these compounds.

Hawthorn also acts as a vasodilator, meaning that it opens blood vessels and increases blood flow. This is especially important in the coronary blood vessels that supply the heart with oxygen.

The herb dilates the vessels by relaxing smooth muscles in the artery walls. Through the use of a natural chemical that acts much like synthetic drugs that are widely used to treat high blood pressure and heart disease, it also inhibits an enzyme that makes blood vessels constrict.

Because of this action, it probably improves the mechanical function of the heart. A better-functioning heart is better able to utilize oxygen, which has a beneficial effect in cases of angina, a crushing chest pain that occurs when blood supply to the heart decreases.

"I’ve used hawthorn to treat angina and eventually have been able to take people off their nitroglycerin medications," says Dr. Herring. "But I’d recommend that you do it only with the help of a physician."

The flavonoids in hawthorn may help keep you from ever having angina pain because they appear to strengthen the structure of collagen, which makes up arteries and blood vessels. When the collagen is stronger, the blood vessels are less susceptible to plaque buildup.

The power to help build collagen is useful in other parts of the body as well. Collagen can be destroyed if you have inflammation caused by rheumatoid arthritis or other types of autoimmune diseases. The consequences can be painful. When collagen in cartilage decays, the connective tissues between bones may disintegrate, and you may end up with bone rubbing against bone, says Dr. Herring. "Collagen is important for all kinds of structures in the body, so you want to hang on to it and protect it," she says.

Hawthorn has a chemical action that helps tone down inflammation. While helping to protect collagen, it may be able to slow down the progression of chronic inflammatory disease, says Dr. Herring. It also helps protect cells from premature aging.

Hawthorn comes in several forms: freeze-dried berries, tincture, capsules, and a concentrated extract that resembles a tarlike syrup. "You can lick the extract off a spoon or make a tea with it. It actually tastes pretty good," says Dr. Herring.

Don’t expect instant results, however. The therapeutic effects take time to develop, usually a period of weeks or months. If you think you might have a heart or blood pressure problem, first get an accurate diagnosis, says Dr. Ben-Arye. After you know what the problem is, you can make your choices about medications and supplements.