Giant hogweed

Rather similar in looks to an overgrown cow parsley, giant hogweed can grow to 10 feet high and can also be harmful to the skin if its sap makes contact.

Whilst perhaps not as difficult to control as Japanese knotweed, it still needs a considerable amount of attention to prevent its spread.

Glyphosate is often the ideal option, as is simply digging it out. Attention however must be paid in terms of covering arms and legs, and wearing a mask if the plant is to be dug out, as the sap and debris can cause a nasty reaction.