The first of three masterclasses took place at Westland Horticulture in Peterborough on March 19.
GCA chief executive Iain Wylie said: "The first masterclass will include a session on merchandising, opportunities for business growth and managing the seasons to make maximum sales and profits.
"There are 28 attending this initial workshop and they will also all go along to a second one in June. The participants will be given extensive coaching and mentoring.
"From the original 28, just 10 will then be selected in September and from those 10, five will be chosen as finalists to attend the GCA Conference in Chester in January.
"At our conference they will make a presentation on what they have achieved during the year. A winner will then be chosen by conference delegates before being presented with his or her prize at the GCA’s annual gala dinner on Tuesday, January 27, 2015."
The next masterclass will be held on Thursday, June 12 and the third on Thursday, September 11. The venues are yet to be confirmed.