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Thorn Weeds are a species of Seed Weeds found in Ancient Waterworks in Wario: Master of Disguise. The Wishstone turned some Seed Weeds into walking plants with spiky heads. The spikes are heavy, so it can't move without firing off a few of them. These plants attack Wario by firing their spikes at him. They can be defeated using Dragon Wario's fire breath.
The Wishstone turned this plant into a hulking beast, but its spikes are so heavy it can't move without firing off a few of them first.