The answer to this age-old question is…sort of. All tea comes from the same species of evergreen plant, Camellia Sinensis. That means that other plants commonly referred to as tea like chamomile, peppermint and rooibos are not actually tea. Shocking, I know! It is the processing of the leaves that determines what type of tea it becomes. Contrary to popular belief, there is no such thing as a green tea plant or a black tea plant. There are many varieties of Camellia but most are used as ornamental shrubbery.
Sinensis vs Assamica
The two main taxonomic varieties used to make the tea that we drink are Camellia Sinensis var. Sinensis and Camellia Sinensis var. Assamica. Sinensis has smaller leaves and prefers slightly cooler climates. Assamica has larger leaves and grows best in warmer climates. Left to grow in their natural state the Assamica tends to grow into a larger tree.
Within those two varieties, there is a lot of genetic diversity. You might hear the words variety or cultivar tossed about but what do they really mean? You can think of variety as a naturally occurring phenotype or observable trait. Cultivar refers to a variety that has been selectively cultivated by man.
The cultivar does not change if a plant is grown in a different place. Tie Guan Yin is still Tie Guan Yin if it is grown in Anxi, China and Muzha, Taiwan. Growers select the varieties they use for many reasons. Drought resistance and cold hardiness are both traits that may help improve production.
This article is just an overview meant to inspire further exploration. I find the best way to discover the different cultivars is to look them up each time you try a new one. There is no better way to learn than to taste your way through them all.