Born and raised in Wanganui, Ms O'Neil was schooled at Mosston Primary and then Wanganui High School. After leaving secondary school she trained as a laboratory technician that took her first to Wellington and then to Auckland, before she travelled overseas.
"I lived in England for four-and-a-half years until I felt it was time to come home so I came back to laboratory work in Auckland," she told the Chronicle.
She met and married her husband Tom and they have raised two young boys - Tim (9) and Joey (7). But while pregnant with Joey, Ms O'Neil was diagnosed with MS and it was a life-changer.
"We were living on a busy street in Auckland and a sign went up advertising retail space, saying 20,000-plus cars a day drive down out street. We thought this can't be good for our health and so we made a quite dramatic move into the country. We had no idea about rural living and didn't know anyone," she said.
But it was that shift to a 1.5-hectare block outside Pukekohe that primed her interest in gardening.
"I think you could say gardening was in the blood but I'd never really had a chance to test it out before."
Her mother always had veggie gardens while she and her siblings were growing up in Wanganui and her grandfather was a market gardener who started Windermere Gardens.
"When we moved to the country it was a bit like a blank canvas as it was flat dairy land. I knew I wanted to have a garden to give us fresh veggies but I never realised how important it would become in our lives," Ms O'Neil said.
With her trusty Yates Garden Guide she set out learning through trial and error. And it was a huge learning curve. "A handy tip I learned from those early days is not to plant the entire lettuce seed packet into a space more suited to half a dozen lettuce, as there are 1000 seeds in a packet."
Their property is on drained swamp and so they made the decision to build raised beds after the first winter "when my carrots floated away". But the bonus is soil that she said is "amazing" for growing in.
"I have about 22 raised beds and grow all our vegetable requirements for the year. I do a lot of preserving, pickling, jam and wine making and have been known to make cheese.
"There's also an orchard with apples, peaches, nectarines, plums, pears, quince, feijoa, elderberry and loads more, and a list of more trees I would like to try," she said.
Ms O'Neil said after a few years of gardening, and starting to feel a little more confident, she received an email inviting her to enter the 2010 Yates Veggie Growing Challenge which involved gardeners keeping a blog about their gardens throughout an entire spring.
She signed up, despite never really doing any kind of writing since school, and although she didn't win that first challenge, she discovered a love of writing.
She took part the next year and won, then followed that up by winning another challenge Yates held, this time in autumn.
"The following challenge I joined non-competitively as Yates had created such an awesome online forum and support network for like-minded gardeners and I still have friends all over the country from the competitions," she said.
"After three veggie growing challenges I found I had created over 130,000 words and hundreds of photos on the Yates website and so my wonderful husband contacted Yates to see what could be done. Yates said they would sponsor a book if their publishers, HarperCollins, agreed," she said.
The publishers did. That was a little over a year ago and now she has a book which is being sold all over the country and in Australia.
Her husband and the boys have roles in her book. Husband Tom is referred to in the book as Hubby the Un-Gardener: "He doesn't have any passion for gardening but will dig on demand". Tim is known as Tim the Helper while his younger brother Joey is dubbed The Joeyosaurus.
As to future books in the pipeline Ms O'Neil says "never say never".
"Once I discovered I loved gardening, I became a little obsessed.
"Then the love of writing threw a new dynamic into the picture.
"Once the Yates competitions finished I still felt the need to write, so I started blogging at gardeningkiwi.wordpress.com where I still blog today. The desire to write keeps me motivated to garden so I'll have something to blog about, and the garden is constantly inspiring me to write. They work so well together."
For more information go to her website: sarahthegardener.co.nz.