Flower

Flowers are a type of plant in Minecraft. While they can be planted on grass and earth blocks, flowers cannot be cultivated like trees, sugar cane, or crops. They appear to spawn in clusters randomly on grass tiles. Before this update (Alpha and Classic), flowers served no useful purpose except for decoration.

As of Beta 1.2, flowers can be collected and used to make Wool Dyes.

Yellow Flower
Yellow flowers can be collected in one hit and placed in a crafting grid to create 2 units of Dandelion Yellow dye.

Rose
Roses can be collected in one hit and placed in a crafting grid to create 2 units of Rose Red dye. They are also somewhat rarer than yellow flowers; usually being alone or in groups of 3-4.