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When taken as herbal medicine, echinacea stimulates our immune systems, raising white blood cell counts and strengthening cell walls. Although it originated in North America, where native Americans used echinacea as something of a cure-all, in the 20th century, Germany is where its popularity first surged. People use echinacea to shorten the duration of the common cold and reduce the symptoms, and to boost immunity and fight off upper respiratory infections.

7/12/14: This week on The Plant Detective: Asian ginseng, Panax ginseng, helps people with Type 2 diabetes maintain healthy blood sugar levels. Both Asian and American ginseng contain ginsenosides, just in different proportions. Asian ginseng stimulates while American ginseng calms, and in the terms of Chinese traditional medicine, Panax ginseng promotes yang energy and cleans excess yin. American ginseng (Panax quinquefolius) does the opposite.

7/5/14: This week on The Plant Detective: They may have different flavors but black, green, white and oolong teas all come from the same plant: Camellia sinensis. They're just processed differently; black tea is fermented, green tea isn't. Unfermented green tea is especially high in catechins, those antioxidants that scavenge the blood for free radicals and are associated with lower rates of atherosclerosis.

6/28/14: This week on "The Plant Detective:" According to archaeologists, human use of tea,  Camellia sinensis, goes back 500,000 years.  The flavonoids in tea are more effective antioxidants than Vitamins C or E - they seem to boost immunity and protect against cavities and ultraviolet rays. More research is needed to find out if tea's flavonoids protect against cardiovascular disease and certain kinds of cancer.

6/21/14: This week on "The Plant Detective:"  Even today, many elderly Chinese still prefer a good ginseng root to health insurance. American ginseng (Panax quinquefolius) is used to aid digestion, treat diabetes, boost immunity, and balance qi, or life energy.

6/14/14: This week on "The Plant Detective:"  Aloe was one of the most frequently prescribed medicines throughout most of the 18th and 19th centuries. It remains one of the most commonly used herbs in the United States today, protecting against ultraviolet rays, relieving the pain of minor burns - and sunburn -  and helping skin regenerate. One study found that aloe vera gel displayed anti-inflammatory effects superior to 1% hydrocortisone cream or a placebo gel.

6/7/14: This week on "The Plant Detective:" For thousands of years, people in India, China, and Indonesia have used gotu kola to heal wounds, improve mental clarity, and treat skin conditions such as leprosy and psoriasis. Today, in the U.S. and Europe, gotu kola in ointment helps heal minor wounds and taken in other forms, it treats varicose veins and chronic venous insufficiency. The Chinese use it to reduce stress.

Don't confuse gotu kola with cola or cola nut. They're completely different plants.

5/31/14: This week on "The Plant Detective:" The rhizome of Zingiber officinale is eaten as a spice, a medicine, and a delicacy. It's an old remedy for nausea, motion sickness, morning sickness, and the common cold. It's also used to help digestion. And although further research is needed, a 2011 review of scientific literature found that ginger appears to be promising for cancer prevention.

5/24/14: This week on "The Plant Detective:" Cloud mushroom, used for centuries in Chinese medicine, shows immunomodulator properties, helping prolong life after treatment in certain types of cancer. And in clinical trials, a compound derived from cloud mushroom, Polysaccharide-K,  inhibited the onset of cancer.

5/17/14: This week on "The Plant Detective:" The harsh living conditions of rhodiola, a plant that grows at high latitudes and elevations, might explain the strong protective compounds it produces. People of the Arctic used it in their folk medicine for everything from increasing endurance and fighting fatigue, infection and depression to increasing fertility, sharpening memory, and reducing the effects of aging and stress.

5/10/14: This week on "The Plant Detective:" For centuries, the root of Astragalus membranaceus has been used in Chinese traditional medicine, usually in combination with other herbs, to support the immune system and fight fatigue. Today, researchers are investigating roles for astragalus in cancer treatment and heart disease.

5/3/14: This week on "The Plant Detective:" Compounds in Common Comfrey (Symphytum officinale) soothe inflammation and help cells regenerate - hence the old names for plant, "boneset" and "knitbone." But toxic alkaloids in comfrey can damage the liver, so be cautious even with external use of this herb.

Age-old remedy can be dangerous.

4/26/14: This week on "The Plant Detective:" Dong Quai, or Chinese angelica, is sometimes called the "female ginseng" for its role as a balancer of the female reproductive system. It's used for menstrual cramps, abnormal periods, and symptoms of PMS and menopause. Dong Quai is not recommended if you're pregnant or breast-feeding or if you're taking blood-thinning medicine, and it can make your skin light-sensitive.