“Know” is a stretch. Plants respond to attack by releasing chemicals (e.g. nettles and grasses), curling or retracting their leaves (e.g. acacia), or by changing their morphology (e.g. holly); but they have no nervous system - let alone a brain - so it’s not like you’re killing an animal.
They have the knowledge and are doing something about it. If other plants can send out this chemical by observing it themselves, that sounds like a reaction from a communication. It may not be cognition like we expect but it is behaving like cognition would. Hard to argue that plants don’t know or care of their friends start dying.
That website is confusing, it doesn’t let you order any dog meat. It also seems to assume I would have a problem with the product? Is that a strategy to make me want it more?