A Waverley business has cut the ribbon on a 900 square metre state-of-the-art tunnel house. Salad Brothers took over the 1.1 hectare site about 18 months ago and aims to produce half a million lettuces a year.

Salad Brothers co-owner Garth Archibald says business was quite rundown when they took over 18 months ago.

Tucked away on a Waverley side street, a South Taranaki business has cut the ribbon on a 900sqm state-of-the-art tunnel house aimed at putting the crunch into sandwiches across the region and beyond.

Salad Brothers took over the 1.1-hectare site about 18 months ago and aims to produce half a million lettuces a year.

Leafy greens have been a quiet contributor to the Waverley economy for most of the last 40 years, but as Salad Brothers co-owner Garth Archibald explained the Lupton Street operation had seen better days.

"When we first arrived it had been left vacant for a while so it was head high weeds all through here. There was another tunnel house similar to these wooden ones here and that was half collapsed and we had to remove it.

"And we've only just a year later got this replacement up and running which is why we had an opening party last week."

Salad Brothers was bringing the farm into the 21st century, beginning with the $350,000 tunnel house.

"It's a step into the future. It's got computer-controlled climate control where this vent along the top opens in relation to temperature and wind speed and certainly helps to keep the whole place at a more even temperature."

Salad Brothers raises up to 60,000 lettuces at a time or about a half a million a year.

The new tunnel can hold 60 percent more plants - referred to as pots - than the old one, and was designed to make harvesting easier.

There was lettuce in every direction.

"There's 16,000 what we call pots in here. We're just sticking to the green frilly in here at the moment. I think about half of all our lettuce is this green frilly. We've got another 30,000 down there and another 20,000 in the six house that are up here and as you'll see down here we go into all the different reds and spiky varieties."

The new 900sqm $350,000 state-of-the-art tunnel house features computer-controlled temperature regulation.

Salad Brothers grew about 60,000 lettuces at a time, or about half a million a year.

It was a nutrient fall technique hydroponics operation.

"As the water flows through, the plants feed and so when the water gets to this end the nutrients are depleted and it all flows back under the ground to the sump at the end here and just gets pumped around and around and then every month or so we just swap it out…

Go to this episode on rnz.co.nz for more details