Dandilion flowers are edible for bearded dragons. If picked from a yard, make sure no pesticides are used on or near that yard, as this poisons can harm, even kill your dragon and they tend to linger in the body, building up over time till they reach toxic levels.
If you don't use any poisons on your lawn nor do your neighbours (as many pesticides, weed killers etc, can easily be carried over by the wind), you can use any dandelions from your lawn, just wash as normal, chop up to the correct size, mix in with their regular salad and let them enjoy. Other edible flowers are hisbiscus, nostraniums (or something like that, can't spell LOL), panseys and other known edible flowers. There is a great list for suitable vegetables, greens, flowers and fruits to feed dragons can be found under nutrition at: www.beaufifuldragons.com
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PHLdyPayne