Yarrow was prized by Native Americans for many medicinal applications and even a recreational stimulant. Like the bark of the White Willow Tree, it too contains a naturally occurring alkaloid known as Salicylic acid that's used in the mass production of "Aspirin". Because of this, if you have a history of Ulcers you should use caution with this herb. Today it's prized for boosting the immune system, as a topical treatment for wounds, and general illnesses. Read more about Yarrow here.
Yerba Mate has recently grown in popularity in the western world. It was traditionally consumed in South America. Today it's considered a healthy alternative to Coffee. Consumers of Yerba Mate often report that it offers much more energy without the jitters or stomach related complaints. This popular tea was originally consumed from what's known as a gourd. A gourd really cool bowl that resembles a coconut with the top cut off. They are also cool for any herbal drink, especially Kava Kava and Yerba Mate.
Let's get scientific about Yohimbe for a second. As far as phytochemist are concerned, Yohimbe contains many of the same chemical constituents found in Kratom. Like many other popular herbs and entheogens it's native to Western Africa. There, it's used as an aphrodisiac.
It also seems to induce a very nice and warm sense of well being as long as you don't take too much. The bark is used, so like any other root or bark the best preparation method is a decoction. Decoctions are made by boiling roots or barks for an extended period of time. It's generally recommenced to use the lowest heat possible when doing so.
WARNING: Some people report extremely negative effects from Yohime. It doesn't bother me unless I take too much. I don't mess with it anymore. It should be taken very seriously and never combined with anything, especially pharmaceuticals. If you do decide to take it, talk to a Dr. first(one that prefers natural methods for improving health instead of pills), and only use extremely small amounts. See bluelight.
Yucca root was cherished among the wise Native Americans. It has been used to treat joint pain associated with osteoporosis and rheumatoid arthritis. The root is chalked full of vitamins and minerals. It's said to be very soothing to the intestinal tract. It's very similar to Echinacea in the sense that it's also a blood cleanser. Phytochemist have isolated and studied chemical constituents found in this root.