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Spiky Plants are strange plants with red spikes that appear in the Mario 3D platformers.
Super Mario Galaxy / Super Mario Galaxy 2
Spiky Plants make their debut in Super Mario Galaxy and Super Mario Galaxy 2. They hurt Mario or Luigi when touched, and the only way to destroy them is by attacking them with a Stretch Plant, spinning a coconut into them, or having Yoshi eat them.
There are three types: the standard variant, a larger variant, and a floating variant. The larger variants, after being destroyed by a coconut, will reveal a Sling Star or Launch Star leading to another planet. The floating variants serve as obstacles in various areas, and are more common in certain galaxies, like the Gusty Garden Galaxy, the Yoshi Star Galaxy, and the Tall Trunk Galaxy.
When touched by the Co-Star Luma, Spiky Plants will retract their spikes, allowing Mario or Luigi to pass over them safely without needing to destroy them.
Super Mario 3D Land
A Spiky Plant in Super Mario 3D Land
Spiky Plants later appear in Super Mario 3D Land. They are smaller in this game, and can be destroyed with any projectile, as well as by whipping them with Tanooki Mario's tail.
Mario Party: Island Tour
Spiky Plants appear in Mario Party: Island Tour with the same appearance as in Super Mario 3D Land. They appear as obstacles in the minigame Goomba to Maneuver.