Mine have been introduced to this little lot:
Spring greens
Watercress
Spinach
Rocket
Pea shoots
Lamb’s lettuce
Chard
Kale
Carrot tops
Carrot
Parsnip
Celery
Brussel sprouts
Fennel
French beans
Flat/runner beans
Mange tout
Baby sweetcorn
Broccoli
Cauli trimmings
Cabbage
Courgette
Cucumber
Dandelion
Vetch
Grounsel
Chickweed
Mint
Basil
Coriander
Thyme
Parsley
Rosemary
Lavender
Apple
Pear
Cherries
Strawberries
Raspberries
Brambles
Mango
Pineapple
Banana
They get two large leaves of spring greens at breakfast and a salad in the evening. I try to give them plenty of green leafy veg and herbs, while not overdoing the high-calcium stuff, and use fruit and sweet things sparingly as an "accent".