Onion seed

Onion seeds are a very special type of seed, as they can grow entire Onions. Various Onion seeds are scattered throughout the world and can be collected to grow an Onion of a matching color. The only place they can be grown is at the Garden. Unfortunately, the Garden is nearly devastated because of the Great Volcano. The three original Onions are found, however. There is no Bulbmin Onion seed, as they are stored in the Ship. For their respective Pikmin, Onion seeds include:
 * Purple Pikmin: Purple Onion seed
 * White Pikmin: White Onion seed
 * Green Pikmin: Green Onion seed
 * Cyan Pikmin: Cyan Onion seed
 * Burgundy Pikmin: Burgundy Onion seed
 * Brown Pikmin: Brown Onion seed
 * Gray Pikmin: Gray Onion seed
 * Silver Pikmin: Silver Onion seed
 * Tan Pikmin: Tan Onion seed

To obtain an Onion seed, one must defeat the boss of one of the more challenging caves and collect the upgrade treasure it held. Then, the cave must be entered again to face a new boss in place of the previous one. Once it is defeated, it will drop the Onion seed. Also after that boss is defeated, it and the boss previous will alternate with each visit.

After having collected an Onion seed and restored the Garden, several glowing spots on the ground will be visible. A humorous cutscene will unfold upon visiting the location, where the Research Pod will go to a spot, and then flip upside-down to eject the seed into the ground. The Garden must be visited for four more consecutive days after this for the seed to be able to grow. If another area is visited instead, the seed will be destroyed, necessitating having to collect another seed from the boss it was initially obtained from. Additionally, several Onion seeds can be planted at once.