Mrs Lofthouse died in March this year, aged 91.
The ceremony was staged by Fleetwood Civic Society in the rose garden of the Mount grounds.
It was an apt place for the tribute as Mrs Lofthouse, the former boss of Fisherman's Friend lozenge firm Lofthouse of Fleetwood, had a particular love for The Mount, with its gardens and hill-top pavilion.
Five years ago, Mrs Lofthouse gave a personal donation of £1 million towards a Wyre Council project to restore the whole of the Mount site to its former glory, with the other £2million coming from Lottery funding.
It was one of many generous donations she had made to the town she loved.
The businesswoman, who turned Fisherman's Friend into a global brand but kept the factory operation firmly in her beloved Fleetwood, was also honorary president of Fleetwood Civic Society.
Doreen's son Duncan Lofthouse, was invited to assist with the official planting ceremony, which was attended by more than 40 people.
Margaret Daniels, chairman of Fleetwood Civic Society, said: "Knowing the affection Doreen had for The Mount at Fleetwood and her love of gardening, a tree in her memory seemed an appropriate way of commemorating and celebrating everything she has done for Fleetwood.
"I was delighted to plant a rowan tree on behalf of the Society in the rose garden in The Mount grounds she loved so much."
After the tree was planted, the assembled gathering enjoyed a warming drink in the Mount pavilion, giving them the chance to see the refurbishments of the building Doreen had such an affection for.
Mrs Daniels thanked the Wyre gardening Team and Mr Arrell for their help and Mr Wilson from Wyre Memorials who kindly provided the commemorative plaque as their contribution to the tribute.
In October it was revealed that Mrs Lofthouse had left a whopping £41.4 million to the Lofthouse Foundation’, which she and her family set up in 1994 to help refurbish her hometown.