The 15-year-old garden designer James Callicott was making his debut as a show garden designer at last week's event. His father showed him pictures each day to take instructions on the planting.
Callicott follows on from Jack Dunckley, who entered a show garden while aged 16 last year, and features again at this year's event.
Callicott's "An Artist's Garden", in the small gardens category, was designed with help from garden designer Kati Crome. He said: "I wasn't allowed on site during the build-up as I'm under 16 so I had to give friends and family instructions by walky-talky, and they sent me pictures using a laptop and dongle. It's really frustrating."
Callicott said that being home-schooled has allowed him to pursue his own interests rather than having to follow the National Curriculum. He has his own website, and currently volunteers at the National Trust's Hughenden Manor garden. "I would like to do an apprenticeship with either the National Trust or Kew," he said.
The winning girl-guiding garden at BBC Gardeners' World Live last month, where all the plants were grown by children, had to be planted by adults because under-16s weren't allowed on site. An RHS representative said health and safety rules stipulated that no under-16s are allowed during build up because construction is taking place.