Matcha bowls, or chawan, are beautifully decorated bowls that are used to make matcha.

Four seasons play a big role in Japanese culture and matcha bowls are no exception. In summer, you should choose a chawan that looks cool and in winter, a warm looking one.

If the bowl has a flower pattern on it, you should be careful when to use it. You should not use a bowl with a flower that is out of season. For example, a bowl with cherry blossoms should not be used in summer or a bowl with fall foliage in spring. Also, you should avoid using it right in the full bloom season. Japanese believe that the flower pattern on the bowl cannot compete the beauty of the real flower. It is always a good idea to use chawan with flowers that are just a bit ahead of season. The same applies to patterns of kimono.

There are lots of written/unwritten rules like this in Japanese culture. It can be too much or unreasonable sometimes, but trying to enjoy and understand them is valuable. The rules like these are what make Japanese culture rich, complex and interesting.
Matcha Fuji no Haru–Ceremonial Grade