NOTE: I am NOT vouching for the safety of this list, as you will see from my personal notes that I don't have a problem with some things that she says are a problem, and other things are cautionary that she doesn't comment on. I saw it, thought hmm....this might give some ideas. Why not keep an reference to it.
The following comes from here.
I've been looking for a list of plants and such that are OK to feed to rabbits, as well as those that are big no-nos. I stumbled across this list while researching as to whether it is safe to feed pigweed to chickens (it seems to grow very well in spots where I have had my mobile chicken pen...)
I call this method of research where I find answers to one question while searching for the answers to another "Planned Serendipity"
The rest of what follows is from http://www.carlaemery.com/newsletter03.htm
Home-fed Rabbits--Rabbits are a little picker than chickens. They are, of course, herbivores. They like to eat at night. In the daytime when I'm working in the garden, I stuff their cages with stuff I know they like: sunflower stalks, Jerusalem artichoke stalks, Bermuda grass, celery and celery root, carrots, prunings from fruit trees. In the morning, there'll be much less, as they eat their way through the jungle. A rabbit in a cage crammed with food is a happy rabbit! I grow wheat and snip off green tops for them. They love that too. Here's more info on what rabbits can and can't eat...
Acacia: no food value, but twigs can be entertainment
Alfalfa: fresh or hay
Apples: all parts
Beans and bean vines (not soybean)
Beets: both top and root of regular, sugar, or mangel
Blackberry bush leaves
Bluegrasses, including Canadian
Bread: dry, or soaked in milk
Cabbage: some is okay, too much may cause goiter
Carrot: root and tops.
Cereals (if fat-free and fresh)
Clovers: any but sweet clover
Corn: fresh or dried ears, fresh or dried stalks.
Fescue: red, etc.
Filaree (stork's bill)
Grains: all types, unless dirty, damp, or moldy
Grapefruit: all parts (don't feed too much)
Grass: Lawn clippings, grass grains, as long as they carry no
insecticides & are fresh
Jerusalem artichokes: tops, stems, or roots
Kohlrabi: all parts of plant okay
Lettuce: all kinds - personal note: be aware that iceberg lettuce can cause problems. Feed VERY limited amounts.
Milk: fresh or sour, as well as milk products
Millet: foxtail and Japanese
Oranges: all parts (don't feed too much)
Peas and pea vines
Potato: but, not peelings, sprouts or leaves!
Rye, rye grass, and Italian rye grass
Spinach: in limited amount
Sunflower: leaves, stalks, or seeds
Sweet potatoes: vines or tubers
Swiss chard: in limited amount
Turnips: all parts of plant
BAD FOR BUNNY:
Some greens are high in oxalic acid in the uncooked state: pigweed, amaranth greens, spinach, comfrey, and Swiss chard. To a small-weight rabbit, especially a young one, these can be a problem. I do feed some spinach and chard to mine because they like it, but I don't give them a whole lot. The plants listed below range from deadly poisonous, to hard-on-a-bunny, to no nutritional value.
Chokecherry leaves or pits
Comfrey --- Personal note: some folks feed this with no problems.
Milkweed -- personal note: yet wild bunnies have been known to eat this no probs.
Moldy bread, moldy anything
Pigweed - personal note: mine will eat the young leaves, they leave the stalk and older leaves
Potato leaves, sprouts, or peels
Soybeans or soybean vines
Sweet clover - personal note -- what's wrong with clover?
Other personal notes: mine will eat melon rinds of all sorts ... plus any flesh I leave on them. I make a point of only feeding one slice per week. Don't want to overdo this wet food at all. Mine do not do well on cabbage itself, they can handle limited amounts of broccoli stalks. I am VERY careful with this family of plants.
For other ideas check out carla's page here.