I-O
The min speed as normally used in the US would be "green-line" which is about 1.27XVs. Less than that and you're behind the power curve. Climb capability is usually limited by when the aircraft stops climbing (500fpm nominal is the norm). Min climb speed is .70 for most operators, and will ensure the aircraft will stop climbing well before the buffet margins are a serious factor.
The only way to climb into a sticky situation is generally to go slower to trade airspeed for altitude, but once you try to level, it won't accelerate, and may continue to lose speed if you are "zoom climbing" to get the altitude. Some operators have the buffet cards, but they aren't actually used that much due to the above reasons.