Maybe, I think if a tortoise ate a bite or two it isn't a problem, since this:http://essmextension.tamu.edu/plants/plant/camphorweed/ says it's forage value so fair for most grazing animals... But I think you should be more cautious & avoid itOk. I have not been able to ascertain whether or not the Heterotheca subaxillaris – Camphorweed is edible.
http://www.fireflyforest.com/flowers/1223/heterotheca-subaxillaris-camphorweed/
Serendipitously, there was a installation wide training exercise yesterday, so I had to take a detour which included a stretch of road with tons of weeds/wild flowers. So this morning, I stopped and took photos of all the flowers. I have identified many of them, but some of them I cannot determine if they are toxic or not. Anyone know if Gomphrena sonorae – Sonoran Globe Amaranth is tortoise friendly?
http://www.fireflyforest.com/flowers/1174/gomphrena-sonorae-sonoran-globe-amaranth/
BTW, I am so in love with this fireflyforest.com website.. highly recommend it, especially those in Arizona. It appears there is a Hawaii section, as well!