Latin Name:Foeniculum vulgare; syn. Anethum dulce, A. foeniculum, Foeniculum divaricatum, F. officinale, Seseli foeniculum
Family Name: Apiaceae/Umbelliferae
We cannot find any research on the suitability of Fennel as a food for tortoises, and although it is not toxic it does have a high sugar content that is not good for tortoises, and there is a reference to the dried leaves being a good insect repellent.
The odd nibble shouldn't do any harm but this is not a plant to offer as part of a regular diet. One variety of Foeniculum vulgare 'azoricum' is grown for its bulb-like swollen leaf base and is eaten as a vegetable, but the same principles apply to all varieties of this garden plant and wildflower.
Although often found growing in the wild, Fennel can also be found cultivated in gardens for its attractive foliage.