Season
Ichibancha (first flush)
The first picking of the year, carrying everything the plant stored over winter, and the most savory. Each later flush is more astringent and cheaper. Bancha is mostly made from the third flush onward and from leaves that have hardened.
In more detail
First flush accounts for something like forty percent of annual volume, and rather more than that by value. Later flushes are more astringent and cheaper, so much of it goes into bottled drinks and processing. Bancha and hojicha are mostly made from the third flush onward, or from leaves left to harden on the bush.