Mr Samant said Prince Harry would like to include the flower at the Cenotaph on Remembrance Sunday to honour India's war dead.
"His elder brother and his father both put a wreath of marigolds down at India Gate at New Delhi to commemorate (India's fallen) so I thought it was poignant to also offer His Royal Highness a marigold as part of the Indian diaspora's centenary commemorations," he said.
1.3 million Indian servicemen were involved in the First World War, with 74,000 killed during the conflict according to Mr Samant.
"His Royal Highness spoke of the sacrifice, and said his father had expressed that to him in great detail, and to remember that sacrifice, and it's very necessary to mark that here," he explained.
"He said he'd add a couple of marigolds into his wreath that he puts down at the Cenotaph if he had the choice.
"I think he recognises that sacrifice himself, it's not a small number we're talking about."
Mr Samant added that Prince Harry said if he made the gesture recognising India's fallen, it would not please everyone.
The Duke of Sussex spoke to soldiers as he made his way around the plots, with military mascots also in attendance.
On Sunday, the Duke will join the Prince of Wales, Duke of Cambridge, the Prime Minister and other national figures to lay wreaths at the Cenotaph, as the nation falls silent on the 100th anniversary of the end of the war.
In 2010 Prince Harry opened the first remembrance field dedicated to those killed in Afghanistan: