Ragwort and tansy have pretty flowers. The problem is that they are noxious plants. Noxious is a term used to mean that they are poisonous to certain animals and people.
There are a lot of names for ragwort. One name, commonly used in the US is tansy ragwort. This isn’t good, because tansy is sometimes used in food and ragwort would be poisonous. Tansy should not be eaten. It isn’t safe to do so.
I have pictures of both plants to show you. They don’t look alike close up, but they both have bright yellow flowers.
The pictures are from Wikimedia Commons.
Illustration of ragwort by, Carl Axel Magnus Lindman 1856 – 1928.