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Flower, 26, punched Hohaia to the ground two minutes into Saturday's Grand Final, then landed a second blow to his face while he lay on the ground.
Wales prop Flower was sent off as the Warriors were beaten 14-6.
The ban until 14 April takes in 10 Super League games and the World Club Series match against Brisbane Broncos.
New Zealander Hohaia had already accepted a one-game suspension for a forearm strike which came before Flower's punches.
Flower was charged with a Grade F offence - the most serious in the sport's disciplinary rules - of "violent and aggressive punching" and "punching an off-guard opponent", a charge which carries a minimum of an eight-game ban.
Wigan rugby general manager Kris Radlinski, who accompanied Flower to the hearing at the Rugby Football League in Leeds, said in a statement: "Wigan Warriors would like to go on record in saying that the RFL disciplinary committee handled a very difficult situation with professionalism and integrity.
"We fully support their assessment of Saturday night's incident involving our player, Ben Flower. We will be making no appeal.
"We would like to apologise to Lance Hohaia and his family and to the St Helens club and fans. St Helens' win on Saturday has been overshadowed by the incident and that is wrong."
In becoming the first man to be sent off in a Grand Final, Flower left his side down to 12 men for the vast majority of the match at Old Trafford, which St Helens won to end an eight-year wait for the Super League title.
Saints chairman Eamonn McManus said: "The sport of rugby league should not be judged by this event, but by how it deals with it.
"We must assist [Flower] in any way that we can and accept him back into the sport. There is a person behind the player, and I am reliably informed by all that it is a good one."
For Wigan, the defeat ended their defence of the Super League crown and the pursuit of a fourth title.
Former Wigan and Great Britain player Martin Offiah told BBC Radio 5 live: "There is a lot of emotion around what was a big occasion but sadly it was in effect ruined by this incident in which I believe both players played their part. It was a sad day for rugby league.
"The sport was on show, it's a big event and the pictures are very graphic and all the apologies in the world won't wipe these away.
"No one can condone that second punch to the head and he's apologised for that but Lance Hohaia must take some consideration for his actions."
Meanwhile, Greater Manchester Police said in a tweet they are investigating "abusive social media activity" surrounding the Grand Final.
Wigan prop Ben Flower has been given a six-month ban - the longest in Super League history - for punching St Helens' Lance Hohaia.