Stefon Diggs went all out for Cardi B's big night ... gifting his girl a flower surprise so big, it had to be delivered on a flatbed truck!!
The touching gesture went down Thursday in New York City ... just hours before Cardi's "Am I the Drama?" was released -- her first album since 2018.
The New England Patriots star was present for the reveal ... and judging by Cardi's reaction, she never saw it coming!!
The finished product was a MASSIVE custom container filled with roses from Venus Et Fleur .