The goal of this article is to broadly define "White Tea." From a processing perspective, it's easily identified--White tea is produced from either tea buds only or tea buds and the first two leaves, which are withered in a humidity-, temperature-, and airflow-controlled environment for a long period of time (up to three days). In the processing of green tea, oolong tea, and black tea, withering is a step that lasts only a few hours at most. Withering reduces moisture content prior to oxidation or firing (which, in the case of green and oolong tea, prevents oxidation from continuing). For white tea, though, withering is the process by which oxidation is arrested--eventually the low heat and airflow will deactivate the leaves' enzymes. For this reason, white tea is technically considered slightly-oxidized. This slight oxidation makes white tea different than green tea, which is fired as early as possible and considered un-oxidized. White tea is called "white" because of the white down that covers the tender buds of the tea plant.
White tea originated in the late 1800's in China's South-Eastern Fujian province (the same province where Anxi and Wuyi oolongs come from). Although tea producers had been sun-withering tea leaves for hundreds of years, the white teas that are recognizable today were made possible by tea farmers in Fuding County (circled on the enlargable map of Fujian province) who developed a special cultivar (a genetically unique variety of the tea plant propogated using cuttings) with large, plump buds--the most important component of white tea. From the new cultivars the tea producers developed the two primary white tea types that are around today--Bai Hao Yin Zhen and Bai Mu Dan, which will be covered in the next entry.
Today, tea producers in Taiwan, India, Sri Lanka, and even Africa have begun producing their own white teas, developing processing that relies on extended withering. More than for any other tea type, though, the market's taste is for Chinese white teas. That is to say, if a tea drinker is told a tea is "White," they'll generally expect it to taste similarly to a Chinese white like Yin Zhen or Bai Mu Dan. This is rarely the case, though, since the other countries I mentioned have their own specific growing conditions and often use other cultivars to produce their white teas. So, the main challenge facing these other tea producers is produce a white tea with distinct and desirable enough characteristics that tea drinkers will recognize that white tea--like black and green teas--can be "done" successfully (if differently) by a number of different countries. I've tried a number of non-Chinese white teas, including a Darjeeling white and whites from Malawi and Rwanda, and I don't think we're there yet--the teas I've tried aren't going to make anyone forget about China's famous white teas. These tea gardens are always experimenting and honing their craft, though, so I wouldn't be surprised if the day came in the next few years when white teas of singular quality start emerging from multiple countries across the globe.