Clos Ostler, A Monopole on Limestone
Updated: 7 hours ago
Clos Ostler is both a clos and a monopole. Its limestone wall encloses one north-facing vineyard near Duntroon in the Waitaki Valley, while a single family owns and farms the site. Pinot Noir is the principal variety, with smaller plantings of Chardonnay and Pinot Gris. The two terms describe something physical and enduring, not a borrowed style.
The most revealing moments often come just before harvest. We taste the berries repeatedly, considering their flavour alongside the acidity, skins, seeds and tannin. A savoury character frequently accompanies the fruit. Its expression changes from year to year, but the recurrence of herbs, earth and spice has become central to how we recognise this place.
More than two decades of vintages allow us to follow that character from the vineyard through separate parcels in the cellar and into the mature wines.
What clos and monopole mean here
A clos is a vineyard enclosed by a wall. A monopole is a vineyard held by one owner. At Clos Ostler, the limestone wall was built as the vines were planted, and scallop shells remain embedded in its boulders. Within that boundary, one family can follow the differences among parcels and varieties under a continuous long-term approach to farming and wine.
The first Pinot Noir vines were planted in 2002. Jim Jerram and Jeff Sinnott had recognised the potential of this slope when the Waitaki was still at the beginning of its modern winegrowing history. The site offered northern exposure, limestone-derived soils and a cool growing season. Its suitability could only be established by growing vines and making wine.
The Roulet Magides family took on Clos Ostler in 2021 through ACG Wines, named for the three Swiss-French brothers Antonio, Connor and Georges. Growing up between Switzerland, Singapore and New Zealand, they came to the estate with a winegrowing inheritance rooted in Peseux and a deep familiarity with Burgundy. The limestone enclosure and the plantings within it created an immediate connection with that history, while the cool Waitaki setting offered a new place in which to continue it.
Their admiration for Jim and Anne Jerram and Jeff Sinnott is inseparable from their attachment to the vineyard. The founders had the courage to plant and persevere when fine wine from this isolated region was still widely doubted. Today, the family works with viticulturist Timbo Deaker and winemakers Sarah-Kate and Dan Dineen to deepen the understanding of each parcel, with the hope of passing both the land and that knowledge to their children and grandchildren.
Read the full story of the Roulet Magides family at Clos Ostler.
The limestone beneath the vineyard
The pale formations around Duntroon belong to an ancient marine landscape. Sediments deposited beneath the sea became limestone, later exposed through uplift and erosion. At Clos Ostler, that parent material underlies the vineyard’s calcareous soils.
The marine history is visible in the scallop shells embedded in the stone around the vineyard and in the boulders of its enclosing wall. Beyond the vines, the Waitaki carries waters from the Aoraki catchment towards the Pacific. The ancient seabed and the river belong to different chapters of the landscape, both present in the view from the clos.
Fossil shells preserved in pale limestone at Clos Ostler, Waitaki Valley, North Otago.
Estate soil tests give a more precise view of the ground. The Ostler Block records pH 6.9, base saturation of 97 per cent and calcium saturation of 89 per cent. The corresponding figures for the Kairos Block are pH 6.7, 93 per cent and 83 per cent. These are measurements of particular samples within the vineyard, rather than a description of every row.
The calcium figures need a little explanation. Clay particles and organic matter carry electrical charges that hold nutrients such as calcium, magnesium and potassium. These nutrients can exchange with those dissolved in the water around the roots. Calcium saturation measures the share of that exchange capacity occupied by calcium. At 89 and 83 per cent, the samples describe a strongly calcium-dominated environment. Measuring the proportion of limestone in the ground would require a separate analysis.
Read these results alongside the soil itself. Depth and texture influence root growth and water storage; structure affects the movement of air and water. These conditions matter through summer in a dry-grown vineyard. Savoury and chalky describe the wines, while soil measurements describe the environment in which the fruit developed.
A long season between the mountains and the sea
The Waitaki Valley connects the inland South Island with the Pacific. Westerly and easterly weather bring different conditions through this corridor. At Clos Ostler, a north-facing slope receives sunlight within a cool, windy setting, and ripening can extend well into autumn.
The north-facing aspect and hillside position are practical advantages within this cool setting. Sunlight reaches the slope, while cold air can drain towards lower ground on clear, still nights, reducing exposure to radiation frost where its path remains open. Air movement also helps the canopy dry after rain or dew. Together, these conditions support the work of ripening sound fruit through a long season. Spring weather, flowering and the approach to harvest still require close attention, but the position of the vineyard materially changes the conditions in which that work takes place.
Harvest decisions are therefore made parcel by parcel. Sugar and acidity are useful measurements, considered with the taste and condition of the fruit. Differences in soil depth, exposure and vine material mean that the vineyard does not reach maturity all at once.
Five Pinot Noir clones, several expressions
The estate’s Pinot Noir plantings comprise 115, 667, 777, UCD6 and Abel. These are different selections of the same grape variety. Their contributions change with the parcel and the season, which is why their identity is retained through separate harvesting and fermentation.
Keeping components apart through maturation gives us time to understand them before blending. We assess perfume, fruit, acidity, tannin and length together. The composition of each wine follows the character of the vintage.
Caroline’s Pinot Noir reflects the season through all five clones. It provides the broadest account of the vineyard, bringing the individual components into a complete wine. It has also supplied the estate’s longest sequence of vintages, beginning with a small experimental release in 2004.
EOS is selected for perfume, power and structure, with prolonged development in bottle in mind. Its composition centres on 667 and 777, with a smaller contribution from Abel. It offers a more focused expression alongside Caroline’s; both wines are made to develop with age.
Waitaki Pinot Noir is an occasional release, selected for a fresh and savoury character. Its place in the range depends on the components available in a particular season.
Chardonnay and Audrey’s Pinot Gris
The white wines offer another way to understand the escarpment. Chardonnay brings acidity, texture and the influence of élevage into especially close focus. The contrast between full malolactic fermentation in 2024 and partial malolactic fermentation in 2025 provides one example of how cellar decisions respond to the fruit.
Audrey’s Pinot Gris takes its name from Audrey’s block. The 2022 combines fermentation in tank and French oak with work on the lees. Its pear and floral character is carried through a dry, textured palate. Each wine has its own identity within the same vineyard.
A record in the glass
Independent tastings offer reference points alongside our own observations. Caroline’s Pinot Noir 2021 received 96 points and the New Zealand Red, New Zealand Pinot Noir and North Otago Pinot Noir trophies at the 2025 International Wine Challenge. EOS Pinot Noir 2022 received Platinum and 97 points at the 2026 Decanter World Wine Awards.
Earlier bottles give these recent results a longer context. The vintage archive brings together contemporary reviews and estate notes from the first releases onwards. It records differences between years as well as recurring perfume, fresh acidity, fine tannin and savoury length.
For a monopole, this accumulating detail is invaluable. Each season adds to the understanding of one bounded place, and each bottle retained allows that understanding to be revisited.
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