Barbara has tended the garden near the hospital chapel since with a group of fellow volunteers. She is keen for more helping hands to join them.
"We are three down now and it would be really good if we got a few more."
Barbara says the garden is of huge value to the hospital and she wishes every hospital had such a space.
Women's health overlooks the garden and in 2013 Barbara received an email from a woman in Belgium who had been visiting her daughter.
"It is a place where you can reflect on life and death and the sense of life and love," the woman wrote.
Greg was educated at Palmerston North Boys' High School and had been a cadet with the electricity department, receiving training in all forms of engineering. As he got sicker he was unable to work.
"It's a terrible thing to end up with, a mental illness, because it robs people of everything," Barbara says.
"He never, ever, voluntarily sought help in a place like this so he always ended up having to be committed. I hate that word."
Greg used to work in Barbara's own garden. "He was my eldest son and he was dearly loved."
Barbara says therapeutic gardens are more common in Australia; she was once invited to present at a therapeutic gardens conference in Melbourne.
Her dream is for all hospitals to have a place of peace and tranquillity. "Some might have but many don't."
In the garden there's a plaque with the words that came to Barbara when she was thinking about what the garden would do. "Plant me a garden to heal the soul, a garden of peace and tranquillity."
She has written about Greg's life and the history of the sensory garden - the leaflet is available to garden visitors.
+ To be a garden volunteer ring Glenda Houston on 350 8850 or email Glenda.Houston@midcentraldhb.govt.nz.