All of the plants below are suitable for consumption by tortoises:

Aloe vera

Antirrhinum - flowers & leaves

Aubretia - flowers & leaves

Bindweed - flowers & leaves

Bramble - leaves

Cactus, opuntia (Prickly pear/Indian fig)

Campanula

Chickweed

Clover - flowers & leaves (both red and white)

Dandelion - flowers & leaves

Dead Nettle - leaves

Gazania - flowers & leaves

Geranium species (perrenial) - leaves & flowers

Hebe - flowers and occasional leaves

Hibiscus - flowers and occasional leaves

Honeysuckle - flowers

Hosta - leaves

Mallow - flowers & leaves

Forget-me-nots - flowers & leaves

Mulberry - leaves

Nasturtium - flowers & leaves

Osteospermum - flowers and occasional leaves

Pansies - flowers & leaves

Pelargonium - flowers & leaves

Petunia - flowers & leaves

Plantain

Rose - petals only

Sow thistle - flowers & leaves

Strawberry (wild and cultivated) - leaves & flowers

Vetch

Viola/Violet - flowers & leaves