I have yet to find a book that tells me which Texas flowers are safe for my little guy. I know about dandelions but what about this one? I usually call them Indian Blankets. Others sometimes call them Indian pinwheels.
Yes, but its not palatable, and your tortoise probably won't eat it.
This is what the Tortoise Table says about it:
"Coreopsis (Tickseed)
There are no known hazards with this plant, so it can be fed to tortoises as part of a wider varied diet. Although the native colour of Coreopsis is yellow (or occasionally orange), there are cultivated varieties in many colours. Coreopsis is closely related to Bidens"