Giant flowers are larger versions of the rose and yellow flower found in Vanilla minecraft. They can only be found in the Garden biome, where they spawn instead of trees.
They each have five Giant Flower Stem blocks, which can be mined by hand. The red has 37 Giant Red Flower blocks and the yellow has 26 Giant Yellow Flower blocks, both must be mined with silk touch.
These blocks cannot be used to made lumber or dye, and are purely decorative.