Milton Keynes Council has the following erroneous statement on its website

Is there any legislation requiring landowners to control weed on their land?
Yes, The Weeds Act 1959 requires that five specified weeds are controlled. In particular the Council aims to limit the growth and spread of Common Ragwort on its highways, parks and open spaces in accordance with the Weeds Act 1959

This is incorrect. The Weeds Act 1959 does not require that these weeds are controlled. It allows the government to make orders requiring their control in specified cases. There is a briefing here on Ragwort law