Why even worry? If the tortoise does not eat it then how can it hurt him?

I had morning glory (read toxic) growing wild in my tortoise pens. I'd pick it and pick it and finally gave up. The tortoises weren't eating it and in fact used it for shade on some occasions.

The only way a toxic plant is a problem is if it gets eaten. If a plant is not eaten it is not toxic to the animal.
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AMAZON REPTILE CENTER