When the bulb on its back grows large, it appears to lose the ability to stand on its hind legs.
The bulb on its back grows by drawing energy. It gives off an aroma when it is ready to bloom.
Exposure to sun light adds to its strength. Sunlight also makes the bud on its back grow larger.
If the bud on its back starts to smell sweet, it is evidence that the large flower will soon bloom.
The bulb on its back grows as it absorbs nutrients. The bulb gives off a pleasant aroma when it blooms.
— Pokédex entries (via PokeAPI)