Hartley was selected in England's 42-man squad on Thursday despite not having played since receiving an eight-week ban for biting Ireland flanker Stephen Ferris during the Six Nations.
The Northampton hooker, who will be available for the Aviva Premiership final should Saints beat Harlequins on Saturday, is bound to have his temperament sorely tested in South Africa.
England have never faced the Springboks on a three-Test tour before and forwards coach Graham Rowntree labelled the challenge that lies ahead as one of the most brutal in world rugby.
Lancaster will meet with Hartley and has already issued Danny Care with a stern reminder of what England expect after bringing the Harlequins scrum-half back from international exile.
Care was axed from England's Six Nations squad following his arrest for drink driving, one of four brushes with the law in recent months.
But Lancaster's call for discipline is directed at the whole squad embarking on the five-match tour.
"We will be sitting down with Dylan and explaining to him exactly what is required to be an international player. We have to be able to trust the players," Lancaster said.
"If we can't trust a player on the field then he won't be selected. We will have a pretty strong conversation and he has to prove to us he is ready to come back into the Test arena.
"Attitude, energy, emotion and discipline should be a given for an England team now.
"We work very hard on our on-field and off-field discipline. What we will have to reduce is our penalty count. That is not just Dylan.
"We can't be giving penalties away and being undisciplined on the field, particularly with Morne Steyne who can kick them from anywhere.
"We are confident the messages we are giving the players are being received. We will make sure Dylan gets that message."
Lancaster only selected Care for the tour because he is confident the 25-year-old, who has given up drinking, has already got the message.
"In order to be an England player on the field you have to be able to lead yourself off the field. Danny needed to reassure me he could," Lancaster said.
"I met Danny. I am pleased with the progress he has made and the maturity he is now showing off the field.
"It is a great opportunity, but equally he knows he is treading a very fine line, but I trust him enough to have the confidence to take him.
"He is a player in form and playing at a good club who are in a big (Premiership) semi-final this weekend."
Care is currently on police bail after being arrested on suspicion of sexual assault, a claim he denies, but Lancaster has been assured the case will not impact on the tour.
"I spoke to the solicitor involved (in the case) and there will be nothing happening during the tour. There is no period where he will be brought back during the tour," Lancaster said.
"I am very much with Conor (O'Shea, Harlequins director of rugby) on this one; we understand the context of what went on that particular evening and Danny's selection is the right one."
England squad:
Forwards: M Botha (Saracens), D Cole (Leicester Tigers), A Corbisiero (London Irish), P Doran-Jones (Northampton Saints), P Dowson (Northampton Saints), C Fearns (Bath Rugby), J Gray (Harlequins), D Hartley (Northampton Saints), J Haskell (Otago Highlanders), T Johnson (Exeter Chiefs), G Kitchener (Leicester Tigers), J Launchbury (London Wasps), J Marler (Harlequins), L Mears (Bath Rugby), B Morgan (Scarlets), M Mullan (Worcester Warriors), T Palmer (Stade Francais), G Parling (Leicester Tigers), C Robshaw (capt, Harlequins), G Robson (Harlequins), M Stevens (Saracens), T Waldrom (Leicester Tigers), T Youngs (Leicester Tigers)
Backs: A Allen (Leicester Tigers), C Ashton (Northampton Saints), B Barritt (Saracens), M Brown (Harlequins), D Care (Harlequins), L Dickson (Northampton Saints), O Farrell (Saracens), T Flood (Leicester Tigers), B Foden (Northampton Saints), A Goode (Saracens), C Hodgson (Saracens), J Joseph (London Irish), G Lowe (Harlequins), U Monye (Harlequins), D Strettle (Saracens), M Tuilagi (Leicester Tigers), J Turner-Hall (Harlequins), C Wade (London Wasps), Ben Youngs (Leicester Tigers).
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