There seems to be a lot of differing opinions on greens. Some say don't give them until at least six months of age, some say 3 months and some let them nibble as soon as they start weaning.
I think you would be fine to introduce now, but it's a matter of not overdoing it. You need to start with only one type of green such as romaine lettuce or coriander and just give a tiny piece, the size of a quarter or a fingernail once a day. If you notice any side-affects such as squishy poo, or lack of pooping or eating or gas, then you need to not give any more. However, if it goes down well, then you can give the same sized piece once a day for maybe 3-5 days before slightly increasing the amount. Then give the increased amount for multiple days (as long as there's no side effects). After two weeks, you can introduce the next leafy green (starting with a tiny amount).
If you do get an ill-effect from one of the greens, wait at least 3-4 days before either trying again with a smaller amount, or before trying a different one.
