Prickly pear cacti are native to the Americas, but they’ve been spread all over the world by humans.
They’re grown for human food and as ornamental plants, and they also work well in desert terraria.
Prickly pear cacti are not only edible for bearded dragons, but some keepers offer their lizards prickly pear cactus pads specifically as food.
There are many species of prickly pear cacti, and they differ in terms of height, morphology, environmental requirements, and color.
Most are green, but others, such as the purple prickly pear (Opuntia macrocentra) are quite colorful. 
As their name suggests, prickly pear cacti bear spines that may injure or irritate your lizard. However, you can often find cacti for sale that have had their spines removed. Note that you may need to prune your prickly pear cactus regularly to prevent it from outgrowing the habitat.