Hanami is an important Japanese custom and is held all over Japan in spring. Hanami literally means viewing flowers, but it generally indicates cherry blossom viewing. It's said that the origin of hanami dates back to more than one thousand years ago when aristocrats enjoyed looking at beautiful cherry blossoms and wrote poems.
Nowadays, people in Japan have fun viewing cherry blossoms, drinking and eating. It is like a picnic under the trees. People bring home-cooked meals, do BBQ, or buy take-out food for hanami. In popular hanami spots, there are even competitions for the best spots. If you do not like a crowd, you can go to neighborhood parks/gardens or other quiet places. The most popular kind of Japanese cherry (sakura) tree which can be found everywhere in Japan is somei-yoshino (Yedoensis). Sakura trees bloom at different times throughout Japan, and the blooming period of somei-yoshino is usually short.