Family: Cactaceae

Origin, Description & Uses
Opuntia robusta, commonly known as silver dollar prickly pear, dinner plate cactus, or wheel cactus, is a large cactus native to Mexico. This striking species is recognized for its broad, rounded blue-green pads that can resemble oversized plates or wheels, along with sharp spines and colorful flowers that are typically yellow. Like many prickly pears, it produces fleshy fruits that may be eaten fresh or used in beverages and preserves. It is often cultivated as an ornamental plant in dry landscapes because of its unusual appearance, drought tolerance, and ability to form dramatic living barriers or specimen plantings.

Risks & Threats
Although Opuntia robusta is not currently known to be naturalized in the Hawaiian Islands, it possesses traits that are cause for concern and could detrimentally impact tropical island ecosystems. This species is highly drought tolerant, spreads readily through detached pads, and can form dense, spiny thickets that crowd out native vegetation and restrict access for wildlife, people, and livestock. Its sharp spines can also injure animals and humans, while fallen pads can root easily and establish new populations. In climates favorable to cactus growth, prickly pears have demonstrated the ability to spread aggressively and become difficult to control. Because of these risks, it is recommended to choose a low risk or native alternative when suitable options are available.

High Risk Traits:

• Broad climate suitability
  
• Native or naturalized in tropical/subtropical climates
  
• History of repeated introductions outside native range
  
• Naturalized beyond native range
  
• Environmental weed
  
• Congeneric weed (other Opuntia are invasive)
  
• Produces spines, thorns, or burrs
  
• Allelopathic
  
• Unpalatable to grazing animals
  
• Tolerates wide range of soil conditions
  
• Reproduces by vegetative fragmentation
  
• Propagules dispersed intentionally by people
  
• Propagules bird-dispersed
  
• Propagules dispersed externally by other animals
  
• Propagules survive gut passage
  
• Tolerates or benefits from mutilation, cultivation, or fire

Low Risk Traits:

• Not a garden, amenity, or disturbance weed
  
• Not an agricultural, forestry, or horticultural weed
  
• Not toxic to animals
  
• No recognized pest/pathogen host
  
• Not allergenic or toxic to humans
  
• Not shade tolerant
  
• Self-incompatible (reduces seed set)
  
• Not unintentionally dispersed
  
• Not wind-dispersed
  
• Not water-dispersed
  
• Not highly prolific seed-producing