SafePlants

Thistles: A Prickly Subject

Thistles, belonging to the genus Cirsium, are a group of plants known for their distinctive appearance and association with various animals and cultural symbols.

Considerations for Pets

• Thistles are often covered in spines, which could pose a physical hazard to pets, potentially causing discomfort or injury.

Considerations for Children

• Like with pets, the spines on thistles may cause discomfort or injury to children.

Scientific Name and Common Names

• Scientific Name: Cirsium (various species)
• Common Names: Thistle, Bull Thistle, Common Thistle, Spear Thistle, Porcupine Thistle, Canada Thistle, Le Conte's Thistle, Rocky Mountain Fringed Thistle, Fringed Thistle, Lacy Thistle, Mountain Slope Thistle.

Taxonomy and Nomenclature

• Kingdom: Plantae (plants)
• Genus: Cirsium
• Species Examples:
  • Cirsium vulgare (Bull Thistle, Common Thistle, Spear Thistle)
  • Cirsium laterifolium (Porcupine Thistle)
  • Cirsium lecontei (Le Conte's Thistle)
  • Cirsium clavatum var. americanum (Rocky Mountain Fringed Thistle, Fringed Thistle, Lacy Thistle, Mountain Slope Thistle)

Morphological Characteristics and Growth Habits

• Thistles are described as forbs/herbs, meaning they are non-woody plants that are not grasses.
• They are known for their "effusive flower heads," typically in shades of purple, rose, or pink.
• Some species can be quite prickly and sprawling, forming colonies with perennial underground stems.

Ecological Role

• Cirsium vulgare (Bull Thistle, Common Thistle, or Spear Thistle) is listed as a noxious weed. The text does not elaborate on the implications of it being noxious.

Quirky Facts

• Thistles have a historical association with donkeys (or asses), as mentioned in one instance of an ass eating a thistle.