I had heard my tea instructor mention several times that tea growers in Japan overcame the country's lack of elevation by shading their teas during the final four to six weeks of the growing cycle. Recently in a Skype class with another student she asked me if I knew of another tea that rose above its low grown status. I didn't. I asked for country of origin. She said Taiwan. I still didn't know. Do you know? It's Oriental Beauty. I am a big fan of OB. I guess I missed the part of the Taiwanese tea lecture where she spoke about the elevation at which this oolong is grown. I did not think Oriental Beauty was a "gao shan cha" or high mountain tea but I assumed it grew at a high enough altitude to produce its flavorful profile. By the way, to be considered a gao shan cha, a tea plant needs to be grown at 1000 m (3,300 ft) or higher. Actual Taiwanese gao shan cha are Ali Shan, Shan Lin Xi, Li Shan, Da Yu Ling, and Hehuan Shan.
What is it about high elevations that produce exceptionally flavorful teas? Here is an explanation from TEA by Gascoyne et al. (2014).
The weather conditions at high altitudes are obviously different. It is colder, which slows the growth of the tea trees but increases the concentration of aromatic oils in the leaves. In addition, thick fog filters the sun's rays in the morning and at night, as well as during part of the day, thus reducing the amount of sunshine to a few hours each day, resulting in the plants producing young, extremely dark-green shoots that contain more amino acids and nitrogen compounds. Moistened by this fog, the leaves are also more tender and, unlike leaves that grow at lower altitudes, they remain supple, which is a good quality for further processing.
Back to Japan. Japanese teas are covered to reduce sun exposure to which plants respond by producing more chlorophyll and amino acids. The resulting chemical composition and physiology of these leaves resemble leaves that grown on high elevation tea plants. Shading ranges from 0 to 90%; sencha is produced from unshaded tea gardens, kabushecha from 50% shaded gardens, and gyokuro and matcha from 90% shaded tea gardens.
Oriental Beauty is not grown in shaded conditions so what is its flavor tactic? The leafhopper Jacobiasca formosansa also known as small green leafhopper, tea green leafhopper, or tea jassid. This insect occurs at low elevations and feeds during the summer. The injury initiates the oxidation process and eventually confers the floral, fruity, sweet, spicy (think baking spices) flavors associated with Oriental Beauty oolong.
I don't know of other low altitude grown teas that are renowned for their flavor. Please share any I've missed in the comments. Did you know that Sri Lanka distinguishes its teas by altitude? You may have read this factoid in my post about comparing an Assam and an Uva.
P.S. For more information about Oriental Beauty, read two posts by Tea Masters: Hsin Chu county Oriental Beauty and A study of Oriental Beauty.