"I put in half a row and everybody wanted it, so I kept expanding year on year on year," he said.
His speciality Asian vegetables are so popular that he will have to expand the carpark on his Whanganui East back section.
The vegetables draw people from Palmerston North, Hawera, Stratford, Opunake and Levin. He gives them a bucket and secateurs and they wander the 5500sq m greenhouses and pick what they want, often spending between $50 and $200.
His only advertising is a Facebook page which gives his hours. It's followed by 473 people. And he doesn't have to pick and process vegetables any more.
The change to his one-man business has doubled his hourly takings - which he said are never high in horticulture.
He's tried some of the vegetables himself, and said luffa tasted pretty good - a bit like zucchini.
In April last year New Zealand Lifestyle Block magazine did an article on him. It was nearly the end of the season, but his business went "ballistic".
"I had phone calls from all over the South Island, wanting to see if I would send stuff down. I wasn't that keen. I was trying to get away from picking and processing."
His plants are grown to order by a Palmerston North nursery. The season is nearing its end, and they will soon be pulled out and the ground prepared for next spring's crops.
During the winter McCulloch will do horticultural work for other people, for wages. He likes a change from being at the greenhouses every day.