Celery leaves - not much nutrition
Leeks - alkaloid toxins
scallions - couldn't find anything on this one, but I really doubt a tortoise would eat any kind of onion or its tops.
I do feed my leopards celery leaves, but it's usually stuff we had in the refrigerator we got for us that is about to go bad. Not much nutrition but no harm in eating it. Not sure about the other two.
These would be the types of things that I wouldn't put on the daily menu, but if you have some leftovers, etc., it shouldn't hurt to toss them in there.
I always throw all my leftover veggies from cooking for my family to the tortoises.
well the funny thing is I did try some scallion before asking,pretty sure wild onion is listed as o.k in moderation,only one of my leopards ate it though,the one thats fighting illness right now. thanks again john