Goldenseal ( Hydrastis canadensis) grows in eastern North America, where it's now threatened in the wild. An alkaloid in goldenseal, berberine, shows powerful antimicrobial effects against a wide range of bacteria, yeasts, and parasites. Herbalists prescribed goldenseal to stimulate the immune system, fight infection, and treat diarrhea. (Podcast: The Plant Detective , 9/13/14)

There's a persistent urban legend concerning the herb, goldenseal: take it before a urine test and you'll get false-negative results for a variety of recreational drugs. Disappointingly for those who try, goldenseal won't mask drug residues in the blood. The idea came from Stringtown on the Pike, a novel published in 1900 by plant pharmacist John Uri Lloyd. In the book, goldenseal causes a false-positive result for strychnine poisoning. (Podcast: The Plant Detective , 9/6/14)

In the 1930s, scientists trying to synthesize estrogen and progesterone for therapeutic uses - and possibly to create a new kind of contraceptive - faced an obstacle: they needed an abundant, cheap source of the hormones for mass production. Chemist Russell Marker discovered a way to extract progesterone from plants, and began searching for one that could yield enough of the hormone. After searching for a decade, he found it: the wild Mexican yam. (Podcast: The Plant Detective , 8/30/14)

The causes of migraine aren't well understood. Neither is the mechanism behind feverfew's proven ability to stop or prevent a migraine headache. Feverfew supplements used in clinical studies to treat migraine contain a standardized dose of 0.2 to 0.35% parthenolide, so if you research this herb, pay attention to dosage details. Pregnant women and children under the age of two shouldn't use it, and people with allergies to ragweed, chamomile and yarrow are sometimes allergic to feverfew. ( Podcast : The Plant Detective , 9/20/14)

The alkaloid atropine occurs naturally in plants like deadly nightshade, datura, and henbane. It can keep your heart rate steady after a heart attack, dilate your eyes - think belladonna - or dry up secretions during surgery. Soldiers carry atropine injectors because it's an antidote to nerve gas. But in high doses, it's hallucinogenic and poisonous. Remember the three fates of Greek mythology? One of them, Atropos, determined the mechanism of death for mortals. Atropine is named for her. ( Podcast : " The Plant Detective ," 10/18/14)

The powerful anti-inflammatory action of harpagoside, a compound in the roots of devil's claw, relieves the pain of osteoarthritis, and many herbalists recommend it for digestive problems. The San of the Kalahari have used it medicinally for centuries. But because devil's claw is gathered wild from the deserts of Southern Africa, where the tubers are an important source of income , there is pressure on the population. In some regions, the current rate of harvest might not be sustainable. Good alternatives to devil's claw include turmeric, yucca, willow, or meadowsweet. ( Podcast : " The Plant Detective ," 10/11/14)

Medicinal use of datura - also known as moonflower - is so ancient, no one is sure where the plant originated. Two important nervous system depressor drugs, atropine and scopolamine, are derived from it. Oracles in the Americas and Greece used it for divinations. Witches in medieval Europe applied it to their skin in ointments. And when modern-day researchers experimented (a risky proposition; one of the researchers died) with those old witches' recipes, they reported intense dreams of flying. Broomstick, anyone? ( Podcast : " The Plant Detective ," 10/25/14)

It's not an old wive's tale: cranberry helps prevent and treat urinary tract infections. And it's not just the acidity: a compound in cranberries and blueberries keeps bacteria from sticking to bladder and urinary tract walls. Cranberries are high in several kinds of antioxidants, including proanthocyanidins, which give the ripe berries their vivid red color. In the 1672 book New England Rarities Discovered , author John Josselyn described cranberries: "Sauce for the Pilgrims, cranberry or bearberry, is a small trayling plant that grows in salt marshes that are overgrown with moss. The berries are of a pale yellow color, afterwards red, as big as a cherry, some perfectly round, others oval, all of them hollow with sower [sic] astringent taste; they are ripe in August and September. They are excellent against the Scurvy. They are also good to allay the fervor of hoof diseases. The Indians and English use them mush, boyling [sic] them with sugar for sauce to eat with their meat; and it

Among the artifacts discovered in the tomb of Egypt's Tutankhamen - objects meant to ease the boy king into the afterlife - were 3,000-year-old bulbs of garlic. Giving as well as receiving, Tut supplied daily rations of garlic to his pyramid-building slaves, for endurance and health. Garlic is a fabulous heart helper: its blood-thinning and anti-clotting abilities may slow down atherosclerosis and lower blood pressure. Raw or cooked garlic strengthens the immune system; The Iowa Women's Health Studies showed that women who regularly ate garlic, fruits and vegetables had a 35% lower risk of developing colon cancer. ( Podcast : " The Plant Detective ," 11/15/14)

Ever since nomadic tribes helped spread wild garlic from Central Asia to far-flung parts of the globe, garlic has helped humans fight microbes. Louis Pasteur recognized its antimicrobial power, as did doctors in WWI and WWII battlefield hospitals, where injured soldiers were given garlic to prevent infection and gangrene. Today's warnings of a "post-antibiotic" future mean garlic's power may turn out to be handy as drug-resistant bacteria become widespread. ( Podcast : " The Plant Detective ," 11/8/14)