Aquilegia is not safe for your Horsefield Tortoise to eat. The plant contains the cyanogenic glycoside, although there has been no issue of either poisoning humans or animals, I would avoid feeding Aquilegia in large amounts to your pet.
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Can Horsefield Tortoise Eat Aquilegia?-SAFE/NOT?
Its seeds and roots are so poisonous; they contain cardiogenic toxins, a host to severe gastroenteritis, and heart palpitations (for humans, anyway). Just like most toxic plants, which can only be recognized by you as a pet, and not the Horsefield itself, this plant has some catastrophic effects which can damage your pet’s body if it accumulates.
Although, many plants on the toxic list do not end up endangering your Horsefield Tort if they are taken in low quantity as part of a varied diet. Nevertheless, prevention is better than cure. Since it is your sole responsibility to make sure your pet is hale and hearty, you need to keep it off Aquilegia.