Crouched on a bank beside a stream, she is putting the final touches to a garden that attempts to convey the solitude of depression. Her creation is one of several at the RHS Hampton Court Flower Show exploring links between health and horticulture.
"The one I've focused on is depression because I have family members and friends who have suffered from it," she says. "Rather than being inspired to do it, I was compelled to do it."
A few days before the opening of the show, her garden, The Outside Room, is taking shape, despite the rain. The periphery of the garden contains lush bright planting, which becomes sombre and sparse as you cross a dark moat on to a crumbling island.
"This signifies the sinking feeling and the darkness people suffering from depression will experience," says Amanda, who became a garden designer after a career in the military.