The programme offers people aged 16 and above the chance to learn from Frost about garden planning and design, work with partners and suppliers to develop product knowledge covering planting and landscaping, as well as learning practical horticultural skills to earn a RHS Level 1 Award.
At other times, students will be working full-time at Homebase.
Garden Academy mentor Adam Frost said: "It can be challenging for our industry to attract young people to gardening and show them that it can be an exciting career.
"Over the last two years the Garden Academy students have really impressed me with how much they’ve achieved – especially putting all of the skills they’ve learnt into practice by helping me build two Homebase show gardens at the RHS Chelsea Flower Show.
"The Academy is a fantastic opportunity for people from different backgrounds and ages to come together to share their passion for gardening and the outdoors and develop it into a great career."
Homebase retail director Graham Heald said: "The Garden Academy has been a great success over the last two years and we’re delighted to be able to offer young people such a fantastic opportunity for the third year running.
"Being able to support and train the future talent of our industry is really important to us. A few of our previous academy students have gone on to work within our plant buying teams, and one of our first year students Kate Saville, is a finalist in this year’s RHS Young Garden Designer of the Year competition, which is an amazing achievement.
"As well as learning and training with some of the best in the business, all students who complete the training scheme will be offered a permanent job at Homebase. "Apply at www.homebasegardenacademy.com before 21 June 2015.