The sculptures are displayed to perfect advantage on a sloping lawn leading down to a lake at the gardens, which are owned by Mr Welch's friends, Clive and Nicki Higgie.
Mr Welch is a rugby-playing dairy farmer with a life-long love of art. But it wasn't until about 12 years ago that he started "messing about with steel".
"Now it's become a deep passion. Making art is something that some people just have to do and I'm one of those people."
Entirely self-taught, Mr Welch uses engineering techniques that he has adapted for his own purposes. He cuts and bends all his steel by hand.
"You could call it performance art," he said of his art-making process.
Corten steel, which has copper in it, is ideal for his work because it rusts to a certain level, but the metal doesn't deteriorate.
Each of Mr Welch's pieces take about three weeks to make; then they spend two months rusting on his lawn.
Many of his sculptures contain shapes that come out of his imagination; but others have decidedly down-to-earth origins. For example, Fingers Up, Fingers Down is an exact replica of a section of a hay mower - magnified 16 times.
"When you are creating, you have a relationship with a piece. Once it's finished you have a different relationship with it," Mr Welch said.
An exhibition of Mr Welch's smaller steel sculptures is opening at Taylor-Jensen Fine Arts in Palmerston North on March 29, and runs to April 23.
For more about Artists Open Studios Whanganui, visit www.openstudios.co.nz.