Then don't leave anything in the ground. They cannot keep growing without energy, otherwise the UK could use them to generate free electricity. Like any other free energy, it's a con. Nature doesn't work like that.You cant dig it as any bits left in the ground will keep on growing.
The plant can certainly hibernate and retain energy. Every time it buds, energy is used. If this is not replenished, it will die. This is why a continuous attack on it will cause it to die. This is also the reason the treatment companies don't want you to touch it because they would be out of business.