Below is a small selection of the types of food your tortoise can eat and things it must avoid.
Plants

Dandelion
Clover
Chickweed
Buttercup
Plantain
Heather
Sow thistle
Hawk bits
Bindweed
Rose petals
Forget-me-not
Fuchsia
Antirrhinum
Hibiscus
Aubrietia
Nasturtium
Pansies
Petunia
Geranium
Vegetables

Cabbage
Spring green
Carrot
Cauliflower
Spinach
Beans
Peas
Brussel sprout
Cucumber
Kale
Cress
Watercress
Broccoli
Parsnip
Lettuce
Fennel
Fruit

Apple
Pear
Tomato
Grape
Strawberry
Melon
Plum
Peach
Blackberry
Apricot
Gooseberry
Raspberry

                 


And some plants that are poisonous to your tortoise:

Lupins, Daffodils, Hydrangea, Lily of the valley, Foxglove, Mistletoe, Rhododendron, Narcissus, 
Rhubarb, Hellebores, Crocus, Bleeding heart, Ragwort, Azalea, Vinca, Hypericum, Peony, Lobelia
Aconite, Tobacco plant & Euphorbia's