Spurs boss Andre Villas-Boas made nine changes for the match and his new-look side began slowly, allowing Tromso to dictate the tempo in the opening stages.
Townsend went close shortly after with a 25-yard strike that Tromso goalkeeper Benny Lekstrom did well to smother.
Nacer Chadli almost broke the deadlock 11 minutes before the break, but his header drifted wide of the post after he was picked out by Townsend's cross.
Chadli blasted another effort wide as Spurs ended the half strongly, but neither side could find a goal before the half-time whistle.
You can follow the second half with Sports Mole's live commentary.