The following list is a good variety of fruits and vegetables (listed in no particular order):
- Dark leafy greens such collard greens, mustard greens, dandelion greens, kale etc.
- romaine lettuce is probably acceptable but not as nutritious as other dark leafy greens. Never feed iceberg lettuce (poor nutritional value)
- spinach (only occasionally due to high oxalic acid levels)
- broccoli stems and leaves
- soaked alfalfa pellets, fresh alfalfa hay
- pea pods
- edible flowers such as hibiscus, nasturtium, dandelions
- berries such as black berries, raspberries, blueberries
- tomatoes (occasionally)
- corn on the cob can be an occasional treat
A variety of fresh and natural prey items is the best choice, and can be obtained from pet stores and bait shops. You can feed items caught outdoors too but be very careful about possible exposure to pesticides. Box turtles kept outdoors will probable hunt down wild insects and other invertebrates on their own, too.
- grass hoppers
- wax worms
- super worms
- red worms
There are commercial box turtle diets available that are marketed as nutritionally complete. I am wary of formulated reptile diets as a long term diet, however, and I would recommend them only as a supplement to a variety of fresh foods.
Vitamin and Mineral Supplements
This is a somewhat controversial area, and the need depends on the diet and housing (outdoors vs indoors). However, it is probably wise to dust the turtle food with a good balanced reptile multivitamin supplement at least a couple of times a week. Turtles kept outdoors under natural sunlight will produce their own vitamin D3 and won't need this vitamin supplemented.
A note on cannibalism: a turtle expert adds that box turtles have been known to resort to cannibalism. This is independent of how well fed they are, and often happens as a result of a box turtle ending up on its back or falling in water. I add this simply as something to be aware of -- make sure if you keep multiple turtles together that there are ample hiding places and no areas where a turtle might end up stuck and unable to get away from its cage mates.