Self-described "Medicine Hunter" Chris Kilham and other proponents of plant-based sexual enhancers say they work in different ways: boosting testosterone, improving circulation, detoxifying the body, increasing neurotransmitters in the brain and creating a relaxed state. The FDA says such claims are "folklore, not fact." Kilham's hot plants and what he describes as their sex-boosting effects:

Tongkat ali: This root found in Malaysia and other parts of southeast Asia increases levels of testosterone and adenosine triphosphate. The latter affects energy.

Rhodiola rosea: Common in Siberia, this root promotes energy, stamina, sexual function and desire. It reduces stress-induced chemicals, resulting in a sense of well-being.

Pausinystalia yohimbe: The bark of this evergreen tree yields yohimbine, a fast-acting central nervous system stimulant that also can increase circulation to the sex organs, particularly in men. Side-effect warnings exist. The ingredient exists in some prescription pharmaceuticals.

Horny Goat Weed: Known in traditional Chinese medicine as Yin Yang Huo, the leafy perennial produces an androgen-like effect that can aid erectile dysfunction, libido and increase sexual vitality.

Ashwagandha: A root used in India for at least 3,000 years, ashwagandha is considered a "life-extending agent" that can boost libido and sexual vitality and reduce stress.

Catuaba: Found in the Brazilian Amazon, the bark of the catuaba is said to increase libido and sexual potency.

Zallouh (Ferulis harmonis): Part of the parsley family, this small shrub is found in the Middle East. Extracts made from the root contain substances believed to dilate blood vessels and stimulate circulation; good for erectile problems and low libido. Side-effect warnings exist.

Maca: A turnip-shaped vegetable from the mustard family found in Peru, where it is a staple food. It can be added to blender drinks, cookies, pancakes and other foods products. It is billed as an "aphrodisiac, stamina-builder and fertility-enhancer."

Siberian Ginseng, Red Ginseng: Both plants' roots are long-heralded treasures of traditional Chinese medicine, said to boost overall vitality, the immune system and sexual vigor.

Chocolate: Yep, which explains why the sweet is such a hit at Valentine's Day. Cocoa is rich in antioxidant polyphenols and contains the stimulants caffeine and theobromine. It contains phenethylamine, which boosts endorphins, and increases brain levels of the feel-good chemical serotonin.

- Source: "Hot Plants" by Chris Kilham