Which of the following plants is considered poisonous to ponies?

Ragwort is considered poisonous to ponies due to the presence of alkaloids, which are toxic compounds that can cause severe health issues when ingested. Both the fresh and dried plant can be harmful, making it crucial for horse owners to be aware of its presence in pastures. The toxins can lead to liver damage, which may not show immediate symptoms but can be fatal over time. This is why it's essential to manage and control ragwort in grazing areas to protect ponies from its toxic effects.

Meadow Buttercup, Bluebell, and Dandelion, while they can have varying degrees of toxicity or may cause digestive upset in large quantities, are not classified as significantly poisonous to ponies in the same way ragwort is. Understanding the distinct characteristics of these plants helps ensure the safety and health of ponies in their environments.