What characterizes a poisonous plant?

A plant that is characterized as poisonous is one that produces toxins specifically to deter herbivores from feeding on it. This evolutionary strategy is a defense mechanism that helps ensure the survival of the plant by discouraging animals from consuming it. The toxins can vary widely in their effects, ranging from mild digestive upset to severe poisoning in herbivores that attempt to eat the plant.

While plants that attract pollinators, have vibrant flowers, or are primarily used for ornamental purposes might play crucial roles in their ecosystems or serve various human needs, these characteristics do not inherently relate to the plant's toxicity. The primary focus on the mechanism of producing toxins highlights the plant's adaptation strategy for protection against herbivory, making this the defining characteristic of poisonous plants.