Hydroe bramble

Hydroe bramble refers to weird green stalks with thorns that can be seen in some areas in Hey! Pikmin. These serve as obstacles that either block the player's path, or pose a passive threat, since they kill any Pikmin that touch them, and can hurt Captain Olimar. Each one can have a different behavior, between staying stationary, advancing and stopping, or moving in and out of place, and each one can also move in a straight line or a curvy pattern.

Although their name and origin is never explained by the game, some facts hint that these these brambles are controlled by the Berserk Leech Hydroe. The plants become more common as the player approaches the later sectors. In the final sector (The Final Stretch) and area (Fragment of Hope), there are several of them, they try to attack the S.S. Dolphin II's pod as it flies away, they block the path behind Olimar, closing him in to the arena in front of him, and are also very quick and aggressive. Finally, the theme of the vines resembles the theme of the final boss.

In Pikmin Eco
The Hydroe Brambles return in Pikmin Eco without the Berserk Leech Hydroe, and presenting as more of an obstacle than an enemy. They only appear after finishing the story mode of the game, only appearing in the Bounty Canopy as extra obstacles to avoid. Although they don't actively attack, touching any bramble is enough to kill any Pikmin and damage the player, making them worth avoiding. Despite this, they can still be scanned and are included in the Piklopedia.