Own goal!!

This is the flower spike of the Acanthus. Eventually all the flowers produce a hard seed pod which, when ripened explodes scattering the seeds. The problem is that it is extremely difficult to get rid of the plant which produces an extensive network of roots, any small part of which will then grow into a another plant. I thought I was being clever to germinate a seed pod a few years ago and plant out the resulting  seedling being completely unaware of the potential problems.