Pure, fresh mint has to be harvested and treated with exceptional, tender loving care to produce the best quality material for Colman's of Norwich.Four Norfolk farmers now cultivate one special variety, Brundall, which was found growing wild in a garden, in order to provide the best fresh mint.

Pure, fresh mint has to be harvested and treated with exceptional, tender loving care to produce the best quality material for Colman's of Norwich.

Four Norfolk farmers now cultivate one special variety, Brundall, which was found growing wild in a garden, in order to provide the best fresh mint.

Colman's of Norwich, a subsidiary of Unilever, insists on using fresh, locally-grown mint, which is processed at the Carrow factory.

The market-leading brand only uses fresh Norfolk mint unlike competitors, which typically import dried material from outside Britain.

The harvesting season usually starts in late May and continues until the end of September or the first week in October, said David Bond, of Norfolk Mint Growers.

The long-standing suppliers to Colman's have been involved for about 45 years and seen major changes in the growing and processing operations, explained Mr Bond, who farms at Heath Farm, Postwick, near Norwich.

Two other members of the consortium are also close to the factory - Crown Point Farms at Bixley, and Ed Wharton, of Winsford Hall, Stokesby, near Yarmouth.

However, one of the first entrants, Stangroom Brothers, have been growing mint since the early 1960s at Hamrow Farm, Whissonsett, between Fakenham and Dereham. Neville, and brother David, also grow 75 acres of blackcurrants, top fruit and a range of arable crops as well as 18ha (44 acres) of mint.

It is a highly demanding and specialist crop and getting the harvest right is absolutely crucial, said David's son, Nigel, who drives the specially-adapted harvester.

"We start the harvest about 4am because the first load has to arrive at Carrow ready for 6am. We're 32 miles away from Carrow and it takes about an hour and we have to provide a steady flow of fresh mint for the factory.

"We normally aim for about five loads a day, but when it is as hot as it has been then we cannot cut quite as much. Usually, we'll send in slightly more in the early morning because the mint has dew on it. A typical load would weigh about 2.5 tonnes to

3 tonnes," he said.

The distance to the factory means that Nigel also takes a turn to drive specially-adapted harvester. Gary Nichols, who works for Charles Wharton Farms, and has been the main mint harvester driver for the past 12 years, cuts the first two loads and takes them to the factory. "Normally, I finish the field and then he comes in and we switch trailers and he's off back to Carrow," said Nigel.

When the crop arrives at Carrow, it is forked off by hand onto the processing line. "By doing that, they can keep fluffing it up. If it does go completely brown and composts, they reject it."

The high summer temperatures have caused additional headaches for growers, but Mr Bond, of Norfolk Mint Group, said that the levels of waste are very low and running at less than two per cent because of the care and attention to detail. "It is much more heat sensitive than peas," he added.

The growers work in a loose form of co-operative - sharing the harvester and tonnage contract. "Some people might grow a bit more one year, but then the other guys will get paid for that on another year. We just take it as an average - a bit like a pea group.

"You've got a tonnage to achieve and you might find. We're doing about 1,050 tonnes of finished product this year. The yield, naturally depends on the age of the bed. Mr Bond explained that there was an additional cost - establishing the bed in the first year.

Nigel said that over a full season, involving three cuts, then about eight to 10 tonnes of leaf will be produced. "What you really find is after about three years the bed will slow down a bit. And then you find it is about five cuts in three years. It gets a bit slow. The vigour goes out of it. The idea would be to have a bed in for no more than 10 to 15 years."

Mint needs careful management and growers have to avoid compaction in the fields. It also needs plenty of water. Nigel said that his fields have had about three or four inches of water for the second cut. An inch a week is what we're putting on at the moment.

The mint harvest has also become far more complicated.

It was Nigel's father, David, who wondered about 15 years ago whether a stripper harvester could be used. A harvester, able to cut 1.8m rows, was designed and

built at Silsoe, once the UK'sleading agricultural machinery research centre.

"They worked out how much weight of leaf and stalk was left behind. Roughly 60pc is leaf and 40pc is stem.

"It got rid of all that waste and we're not carting all that waste up to the factory and then chucking it out," said Nigel.

He has one very keen consumer at home. His young son, Charlie, aged four and a half, will only eat sandwiches made with Colman's Mint Sauce and cream cheese.

He loves it and has been eating mint for the past two years!