Armored Nut

The Armored Nut is a treasure in Pikmin 2. It is a small that falls under the Xenoflora Series. It is found in the Wistful Wild inside a Creeping Chrysanthemum.

As Olimar's notes on the treasure indicate, it's location lines up perfectly with where the Onions - specifically the Blue one - landed at The Impact Site in.

Collecting the treasure
The Creeping Chrysanthemum that is nearest to the Hole of Heroes has the Armored Nut. The path the Pikmin take back to the Ship is filled with a variety of enemies that will likely all need to be killed, such as the Cloaking Burrow-Nit and Yellow Wollyhop in the area with the bridge, and the Decorated Cannon Beetle close to the Ship itself. The roaming Gatling Groink, if it has not been killed, is a priority, as it may ambush Pikmin carrying the Armored Nut back.