"en âge de les avoir vus pousser"

what does this mean?

>> en âge de les avoir vu pousser <<

-- literally: "in age to have seen them growing"
-- = "old enough to have seen them growing"

Oh I see, Google tells me this nice expression was taken from a report about the Parisian bourgeoisie.

Here the full sentence:
"A l'ombre de somptueux arbres centenaires, quelques membres du club, en âge de les avoir vus pousser, ... "

Which translates as:
"Under the shadow of magnificent hundred year old trees, some club members who were old enough to have seen them in their infancy..."

http://fr.news.yahoo.com/64/20100627/tfr-la-bourgeoisie-parisienne-dfend-son-a2f96e4.html