The £340m deal, first submitted in December, will see Homebase disappear from the UK market, to be replaced by Wesfarmer's owned Australian brand Bunnings.
Managing director Richard Goyder said: "We welcome our new employees and are excited about the opportunity to bring the best of Bunnings to the UK and Ireland."
Scotts Miracle Gro is preferred partner in Australia. General manager Sheila Hill said: "I hope it's going to be good for us. They know us and our brands."
Mr Fothergill's is Bunnings seed supplier as well as Homebase's in the UK and said Bunnings "dominate the market" in Australia.
Homebase horticulture category manager Andy Goddard said: "It will be interesting to see how things pan out. It's all positive I think."
Wesfarmers plans an additional investment of approximately £500 million in the Homebase team and assets to build a new Bunnings-branded business over three to five years.
Goddard said it was too soon to tell how supply might change but added: "If someone is willing to invest it's got to be a positive thing."
He said Homebase's plans for 2016 had not changed because of the buy-out. He said it was "more of the same" with larger specimens, eat your own rather than grow your own and more planted containers and instant gardening.
Goddard said the Homebase Garden Academy attracted 1,500 applicants for 40 places and that Chelsea Flower Show is a possibility for 2017. Homebase was believed to have planned a garden with Ann-Marie Powell designing for 2016 that did not progress.