When I try to add variety to my tort's diet, I look up the type of plant to see if it's safe, and then I give it to him if it is. My problem is I don't know what kind of leaves have what.

Here is what he gets on a regular basis:
-dandelion leaves and flowers
-stonecrop
-hibiscus leaves
-baby lettuces and endive from spring mix (he doesn't like the other stuff in it)

Which of these has a lot of calcium? And what are some other common garden plants or weeds that I could add to his diet? I'm not a plant person, and my mother really isn't either, so all the plants in the garden she got because they "look pretty", she doesn't know the names for most of them.

Mullberry leaves are high in calcium. Also opuntia cactus.

While the list is corrupted from being transferred through so many versions, this article has the calcium levels (in milligrams per 100 grams of food) of several foods in the 4th column, and the calcium/phosphorous ratio in the 6th.

https://sites.google.com/site/tortoiseli...es--plants

WOW! Thanks for this Mark! Corrupted or not...it's still in the ballpark. I didn't realize that collards would be in the same range as opuntia and mulberry leaves.