Ongoing bad weather is hitting New Zealand's $35 million Northern Wairoa kumara growing epicentre hard.
"We're two to three weeks behind schedule," Doug Nilsson, Northern Wairoa Vegetable and Produce Growers Association president, said.
"If it stays quite cool and not very good weather, it could affect early season production in January."
Constant daily small quantities of rain for almost two months means growers have been unable to plant out as many as usual of the thousands of cloche-covered kumara beds essential in the process of producing fresh new-season kumara for Kiwi dinner plates from late January.
The season's start is among the most challenging in Nilsson's more than 20 years in the industry.
"There have been very few days here without rain since 20 July. We've had at least five mls of rain almost every day."
Nilsson is 25 per cent behind schedule planting out his kumara beds - currently the main task for kumara growers. Kumara beds house the young plants from which cuttings are taken to go into the ground, these in turn producing new season kumara.
He said the weather meant producers had been forced to set up their kumara beds in sub-optimal conditions.
The Northern Wairoa kumara grower is planting out 7000 metres of kumara beds, spread around different growing sites. Wind is also causing havoc for staff trying to put the kumara beds' plastic cloche covers in place.
Growers are desperately hoping for a break in the weather.
"We'd like a good stable weather pattern to come through with five to 10 days of optimal weather," he said.
"This would help ground to dry out and warm up."
About 1200 hectares of kumara is grown in Northern Wairoa each year. The area varying between seasons and Nilsson said the current prevailing unstable weather meant some growers would opt to put in more beds to help ensure total seasonal production wasn't affected.
Latest available figures show there were 19,500 tonnes of kumara produced in Northern Wairoa last season.
Traditional red kumara is still the main kumara type grown in New Zealand. Orange-fleshed Beauregard kumara is increasingly popular, now making up about 45 per cent of sales. Its popularity has steadily increased since it was introduced in 1995. Purple-fleshed kumara is also developing a niche market.
Growers start putting kumara beds in from mid-July, typically ending this growing production phase about mid-October, with the activity peaking between August and September. Cuttings are taken from cloche-covered kumara plants about two months after they go under cover. Staggered plantings from cloche into ground typically run from mid-October, ending mid-December.
Harvest runs from late January until about mid February. Kumara is then stored, with the vegetable available to consumers for the coming 12 months - until the new harvest begins in late January the following year.
Start times for kumara beds and planting their output into the ground, vary around Northern Wairoa. Light friable soils are planted earlier than the heavy ground many farmers grow their kumara on.
Nilsson said the ongoing challenge from recent constant rain didn't come as part of total seasonal rainfall being high.
"In fact the season's rainfall has been below average."
It was rainfall frequency that was the issue, he said.
More than 90 per cent of New Zealand's kumara crop is grown in Northern Wairoa with small pockets in the Far North, south Auckland and Hawke's Bay.
Production is still predominantly family-owned with economies of scale causing transition towards fewer but larger kumara properties. Grower numbers have declined over the last 20 years with about 15 growers now producing 80 per cent of Northern Wairoa kumara.
"That's fewer than half of what there was 20 years ago," Nilsson said.