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He was in Dunedin recently hosting a tasting of his wines at Rhubarb in Roslyn.
A former GP and now co-owner of Ostler vineyard, he and his brother-in-law, winemaker Jeff Sinnott, planted vines in 2000 on north-facing limestone slopes in Priests Rd near Duntroon.
They had been on a fishing trip and came back with a vineyard - or at least land for one, Mr Sinnott has said.
He thought the limestone soils were similar to that of Burgundy in France, which is the home of great pinot noir.
Around the same time, Howard Paterson was developing a company to sell vineyard land a little further up the valley at Otekaieke, so after agonising over the matter, Dr Jerram and Mr Sinnott and their families bought the land and started planting.
At the time, Dr Jerram said everyone, even in Central Otago, thought the valley - with its maritime climate - was too cold to ripen grapes, and he admits it is certainly "on the edge".
In December 2006, the year the icebergs came up the coast, it was so cold fruit did not set on the vines so they harvested none of their own in 2007.
Instead they made wine from grapes grown further up the valley and from Central Otago, and now they have also planted a small vineyard among others at Lake Waitaki.
Those who did not have frost protection in spring have little crop this year, he said - and added he was fighting early autumn frost in April, four to six weeks before the grapes were ready for harvest.
Theirs is one of the last grape crops in New Zealand to ripen.
However, wines made on the cool climatic edge are often the most exciting, he says - something the Central Otago growers used to say until they realised that most of them weren't really "on the edge".
That edginess and the limestone soils certainly give unique flavour and structure to Ostler's wine, judging from the three vintages they have managed to make from their vineyard.
Ostler Audrey's pinot gris (named after Dr Jerram's mother Audrey Ostler) from both 2006 and 2008 (about $35) stood out as remarkably textural, creamy and savoury, especially when compared with Ostler's elegant but fruit-salady 2008 pinot gris from Blue House Vineyard further up the valley, which is on schist rather than limestone.
It has been suggested that aromatic varieties, such as pinot gris, will do particularly well in the Waitaki, and while I'm waiting for more evidence, the few I've tasted from Ostler and other growers certainly show great promise.
A vertical tasting of three vintages of Ostler Caroline's pinot noir (named after the late Caroline Plummer who helped in the vineyard and after whom the Caroline Plummer dance fellowship at Otago University is named) showed the development of the vineyard.
The first tiny vintage was the 2004, which is still perfumed and has a savoury hint and persistent finish, although it is ageing.
The 2005 shows the effects of a cool summer with its edgy, herbal flavours, but the recently released 2006 (about $50) is superb.
It has lovely savoury mushroomy, forest floor characters with gently sweet strawberryish fruit, and an intense, powerful finish.
It is completely different in style and structure from the dark berry and spice Central Otago Grower Selection Pinot Noir Ostler made in 2007 ($35) when it had no fruit of its own.
If this is an indication of what limestone-grown Waitaki pinot noir can do, then there's a great, if climatically difficult, future for it.
For more information visit www.ostlerwine.co.nz.