when does pampas grass flower

they flower from june onwards. it is a bit young if it is only 2 yrs or do you mean you have had it for 2 yrs. How big was it when you got it?
it also likes a sunny aspect so that could be a reason for the delay if it isnt in a suitable spot.

it will flower when its ready but there are many factors ie heat,cold,placement,type etc realy but it will happen

I've never known a pampas bloom in June, Seaburn!? Usual time is September or October for most - it probably means the plant needed to mature before producing plumes and as said above, they do like sunshine or at least an open aspect.

Mine is always around September - October (though I know I'm in a different climate), but we also had some when we were back in England and that was just the same.

there is a big one in my daughters school grounds and it puts its plumes up end of june and if its lucky they stay insitu till october. if unlucky the kids pull them off :o)
perhaps it is just in an odd spot for it.

I wish mine would bloom that long - I love them when the wind blows, reminds of a Palomino horse mane. : -)