Taiwan did have some wild tea trees growing naturally on its soil, but it didn't use those to start its tea production in the 19th Century. Instead, it imported tea tree plants from Fujian. From MinNan (south of Fujian) came the Tie Guan Yin varietal as well as the method of rolling the Oolong in a ball like shape. And from MinBei (north of Fujian) came the tree that gave birth to Luanze (Qingxin) Oolong and its subsequent variations (Qingxin DaPa, Si Ji Chun, Tsui Yu, Jinxuan...). Taiwanese tea researchers have now exactly identified the origin of Taiwan's main tea varietals. Contrary to common knowledge, they don't come from Wu Yi Mountain itself, but from a place 2 hours drive away.
The tea varietal is called Ai Jiao (meaning 'little foot') Oolong. Actually, Teaparker (updated link) has pictures that show that the trees are not that small: they reach until one's neck. These trees are growing at low altitude and there are not many left of them. Why? For farmers, this varietal is not producing many leaves (the same drawback luanze oolong has vs Jinxuan). But the most interesting feature of this tree is that it grows in shallow water of a river.
From the leaves, you can see that it has been roasted quite heavily, like traditional Oolong. The first brew tastes very different from Taiwanese Oolong. The moisture and dampness of the river are the main fragrance and give its special sticky and full mouthfeel. A very long one. The second brew and the smell of the wet hot leaves, however, are very much tasting and smelling like a classic 'Dong Ding Oolong'.
Here we had our confirmation that Ai Jiao Oolong is the mother of all Taiwanese Oolong varietals!
This last picture is not Ai Jiao Oolong (I forgot to take the picture). These dry leaves are roasted WenShan Baozhong leaves from my selection. However, Ai Jiao Oolong looks very much like this.