Hi Sebastien,
Welcome to the Forum, and congratulations on your new tortoise. What species is it? There is nothing nicer than a good outdoor enclosure for a tortoise, and in addition to making it interesting, with plants, hidey places, rocks, etc. it's important to make it secure, as tortoises are amazing escape artists (they can climb up walls and burrow under fences). Horsfields (Russians) are notorious for escaping, and I've attached two photos to show you what tortoises are capable of.
Regarding landscaping and various things to take into account, have a read of our page on outdoor enclosures here:
http://www.thetortoisetable.org.uk/tort ... _x3_h_P0qR
As someone else has said, you can use our Plant Database to choose appropriate plants, but it's wise not to have a substantial plant near the walls of the enclosure, as they can use them as a ladder to climb out. It's nice to have edible plants in the enclosure, but they might be eaten to the ground immediately, so plants that are edible but not as favoured by most tortoises are good -- things like dwarf Hebes and decorative grasses can work well. And you can use the filter tool to produce lists of plants on our database that are all edible.
Good luck and let us know how you get on.
Nina
[attachment=0]Tortoise climbing fence.jpg[/attachment][attachment=1]Tortoise climbing wall.jpg[/attachment]