"From my work with mental health clients I realised there is a lot of joy to be found in gardening. It really grounded them and I thought it might help us as well,'' McNicholas said.
Initially they started growing misi luki bananas, before settling on blueberries as their main crop.
The popular berry can be grown on small blocks and the bush shrubs are prolific. Blueberries are also known as a "superfood" for their high levels of antioxidants and vitamins.
The 6ha property comprises four blocks of about 2000 net-covered blueberries covering about 3ha. Cattle are grazed on the remainder.
"We are a small orchard by any measure. We are too small for the export market so we concentrate on selling locally. Luckily the Bay of Islands is booming,'' Topzand said.
About 10 years ago they set up a charming icecream shop on the property, which lures the public in with large icecream cone signs on the main highway north of Kerikeri.
Once inside, customers find a secluded spot away from traffic noise with inviting umbrellas and chairs arranged outside and comical signs hinting at the couple's quirky sense of humour.
Topzand said the fresh blueberry icecreams are a hot item, with the secret being "more blueberries than icecream".
The couple also take a retro caravan to local markets, festivals and events in the area.
Popular items - all featuring blueberries - include icecream, frozen yoghurt, coconut icecream and smoothies, as well as fresh baking and coffees.
McNicholas loves to make preserves such as jams and relishes from blueberry seconds, and enjoys trying different combinations of ingredients.
The picking season lasts from around mid-October until late March.
They grow about 15 different varieties to ensure berries are available at all times for the daily picking roster.
Topzand said the property's rich volcanic soils are exactly the opposite to the needs of the blueberries.
"This is totally the wrong soil. We are volcanic whereas blueberries like peaty bogs. We correct that by using untreated pine sawdust to alter the soil acidity. It has the added advantage of acting as mulch,'' he said.
"We also feed them every week by fertigation [fertiliser fed through the irrigation system].''
Blueberries prefer some chilling hours to set fruit and leaves.
"Luckily we do get enough frost here.''
Blueberries take about five years to fruit but, once established, will last about 30 to 40 years.
"I've seen some in the Waikato that look like large trees with big stumps,'' he said.
The couple credit the help of growers group Blueberries NZ for help with establishing their business.
"They welcome everyone, including the smallest orchards like ours.''
Cultivars of the rabbit eye variety make up most of the plantings.
While blueberries are regarded as easy to grow, they can be susceptible to fungal disease, including Botryosphaeria stem blight. This causes the dieback and deaths of blueberry plants.
The disease cannot be treated, and the only measure is to practise good orchard management by keeping the plants as strong and healthy as possible by fertigating, spraying copper to prevent blueberry rust and providing seaweed for general plant health, mulching and irrigating. Affected plants have to be removed.
Comfrey and salvia companion plants attract bees from the 20 hives kept on the property by a local beekeeper.
The other main challenge is keeping pests out, especially birds. The couple's dog keeps a keen eye out for any intruders.
Up to six pickers pick about five tonnes a year on the property.
"In comparison, some of the large orchards in the Waikato pick five tonnes a day,'' Topzand said.
The fruit is picked ripe and is chilled immediately in the packhouse, where it is packed into recyclable punnets and straight into the display fridge in the shop or taken to the local markets.
McNicholas said she was a stickler for managing the health of the pickers, keeping their picking containers small so they looked after their backs.
A side business is making commercial icecream machines, such as the one used in the shop, which can churn and quickly create hundreds of ice creams.
Called the Whip It, the machine has been developed to be on view to customers as a form of performance art. It was also really important that it be easy to clean thoroughly for hygiene.
In the off-season, Topzand heads off around New Zealand to showcase his creation.
"It's all hard work, but we love it,'' he said.
