B737 captain reported adding a slight nose up trim during rotation which activated the takeoff warni...

Narrative:

Upon rotation; I trimmed rear a little due to excessive rotational force needed. That activated the takeoff configuration warning as we rotated. Airborne; the warning silenced. Upon the landing gear up call; the first officer (distracted by the warning) raised the flaps from one to zero. I did not notice. At 500 ft I noticed the first officer raise the gear. Reaching 1000 ft; I called flaps up. I noticed; at that point; that they were already up.I was informed by the first officer later that what had occurred was the configuration warning distracted him from the normal flow. He realized he had raised the flaps after they were already up; and seeing that we were already plus 20 over takeoff ref; chose to leave them up rather than distract me and put them back down or converse about it.

Original NASA ASRS Text

Title: B737 Captain reported adding a slight nose up trim during rotation which activated the takeoff warning horn. Once airborne; the Captain commanded gear up and the confused First Officer raised the flaps. The gear was raised at 500 ft.

Narrative: Upon rotation; I trimmed rear a little due to excessive rotational force needed. That activated the takeoff configuration warning as we rotated. Airborne; the warning silenced. Upon the landing gear up call; the F/O (distracted by the warning) raised the flaps from one to zero. I did not notice. At 500 ft I noticed the F/O raise the gear. Reaching 1000 ft; I called flaps up. I noticed; at that point; that they were already up.I was informed by the F/O later that what had occurred was the configuration warning distracted him from the normal flow. He realized he had raised the flaps after they were already up; and seeing that we were already plus 20 over takeoff ref; chose to leave them up rather than distract me and put them back down or converse about it.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.

Attributes
ACN	1369819
Time
Date	201607
Local Time Of Day	0601-1200
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	B737 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	Initial Climb
Flight Plan	IFR
Person 1
Function	Captain Pilot Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Last 90 Days 156 Flight Crew Type 8400
Events
Anomaly	Deviation - Procedural Published Material / Policy

B737 captain reported adding a slight nose up trim during rotation which activated the takeoff warning horn. Once airborne; the captain commanded gear up and the confused first officer raised the flaps. The gear was raised at 500 ft.