What are the soil and climatic conditions suitable for growing tea?

The tea plant, Camellia sinensis, likes a tropical to warm subtropical climate. In the tropics, it can be grown at fairly high altitudes, whereas in colder areas (like the U.S.) it can only be grown at lower altitudes, as far north as Washington State and South Carolina. The plant has high water requirements; it grows naturally in areas with a wet summer / dry winter pattern of rainfall, but it can be grown in areas (like Washington state) with the opposite pattern.

The plant has very low nutrient requirements in its native habitat, and can even grow naturally on exposed rock faces where there are few nutrients. However, when the leaves are harvested for tea, its nutrient demands become much higher and it needs continual application of new soil, compost, or fertilizer.

You can read in more detail about which regions of different countries are most suitable for growing tea on this page about tea growing regions. I also wrote a blog post fairly recently about why the U.S. does not grow more tea, which discusses these climate issues in more depth.