A bowl of punch turns a backyard of rugged individualists into a group with a mission, says cocktail expert David Wondrich, who has written a book, Punch, on the subject.
Wondrich serves his in small glasses so that guests "have to go back for frequent refills", he said, "and every time they do, a new conversation starts."
It also provides convenience for the host.
When you are expecting a yard of guests it's nice not to have to play bartender, too.
Fruit, spice rum, gin and even white wine evoke summer as a centrepiece drink served in a gleaming chilled bowl.