Poison Piranha Plant
From the Super Mario Wiki
Poison Piranha Plants are variants of Piranha Plants that will appear in Super Mario Odyssey. They spit poison when they see Mario, which creates a puddle if it touches the ground. When Poison Piranha Plants are about to spit poison, their heads become purple.
Poison Piranha Plants are found in the Iron Road section of the Wooded Kingdom. If Mario throws Cappy at one, it will swallow him, stopping them from spitting poison. They can also be defeated by running into them in this state. However, knocking a rock into a Poison Piranha Plant will cause it to swallow the rock instead, allowing Mario to capture it with Cappy. When controlled by Mario, they gain his hat and his mustache, and the player is able to spit poison by pressing . Larger Poison Piranha Plants that spit bigger balls of poison also appear.