Saw Briers

When a planet in the Milky Way Galaxy blows up it sends chunks of that planet towards Earth. Before long larger chunks of that planet hit Earth and deposit seeds. These seeds start to grow with the first rain. A small town Sheriff and an Army Major start working together to fight these plants that look just like our saw briers on Earth. The problem is that these saw briers from Tiber Three have a taste for blood and they can uproot themselves to move around and find their next meal. Are you in their way? Could you be their next meal? God I hope not. It is a slow and very painful way to die.