Clos Ostler: A Monopole on Limestone
Updated: Aug 29
What more than two decades have begun to reveal about one vineyard in the Waitaki Valley.
By Connor Roulet Magides
In the final weeks before harvest, we taste the Pinot Noir berries repeatedly. We are looking for the point at which flavour, acidity, skins, seeds and tannin have reached maturity together. At Clos Ostler, another character frequently appears alongside the fruit: a distinct savouriness, already present in the berries before they enter the winery.
I have encountered it in different parts of the vineyard and in seasons that otherwise bear little resemblance to one another. Some years are warmer and more generous, while others are cooler and more tensile. Yet this quality returns. It may present as dried herbs, earth, spice or something more difficult to name, consistently extending the fruit into another register.
Its origin lies within the terroir of Clos Ostler: the limestone beneath the vineyard, its northern exposure, the movement of water through the soil, the wind and the long, cool season. The vine experiences these conditions together, and the wine carries their combined expression.
After more than two decades, this has become the most useful way for us to understand Clos Ostler. Every season leaves its own impression, sometimes emphatically, but certain qualities persist through that variation. The identity of a vineyard is revealed by what continues to return.
Clos Ostler at a glance
Location | Waitaki Valley, North Otago, New Zealand |
Vineyard | Eight-hectare single-vineyard monopole |
Aspect | North-facing limestone escarpment |
Geology | Ancient marine limestone |
Principal variety | Pinot Noir |
Other varieties | Chardonnay and Pinot Gris |
Pinot Noir material | Abel, 667, 777, 115 and UCD6 |
Fermentation | Individually in barrel by clone |
Maturation | Every clonal lot retained separately through élevage |
Blending | Determined after approximately ten months |
Pinot Noir expressions | Caroline's, EOS and Waitaki |
One bounded place
Clos Ostler occupies a north-facing limestone escarpment in the Waitaki Valley of North Otago. The vineyard extends across eight hectares and is held as a single monopole. Its dry-stone wall, built by Roy Stringer during his seventy-third and seventy-fourth years, gives physical form to the idea of the clos: one defined place, observed and cared for as a whole.
Every Clos Ostler wine begins within this boundary. This provides a continuity that becomes more valuable with each passing season. The same family can follow the same vines and parcels over time, retaining a record of how they respond to dry years, cool years, early seasons and prolonged autumns.
The vineyard remains young beside the historic vineyards of Europe. Its first two decades have nevertheless provided enough vintages to begin distinguishing the character of an individual season from the deeper tendencies of the place itself.
That understanding cannot be hurried. It develops through repetition: walking the same rows, tasting the same parcels, retaining their differences through élevage and returning to the resulting wines after years in bottle.
A marine landscape beneath the vines
The pale escarpments of the lower Waitaki are the remains of an ancient marine landscape. The limestone beneath Clos Ostler originated in sediments deposited when this part of New Zealand lay below the sea. Geological uplift and erosion subsequently exposed the calcareous formations that now define parts of the valley around Duntroon.
Across the vineyard, this parent material gives rise to free-draining soils of relatively low fertility and unusually high calcium saturation.
Analysis from the Ostler Block records a pH of 6.9, base saturation of 97 per cent and calcium saturation of 89 per cent. In the Kairos Block, the corresponding figures are pH 6.7, base saturation of 93 per cent and calcium saturation of 83 per cent.
These figures are significant because they describe an unusual root environment. They do not offer a simple chemical translation from soil to flavour, but they help us understand the physical conditions in which the vines grow and mature.
Calcium is associated with soil aggregation and the relationship between mineral particles, pore space, air and water. Together with the underlying limestone and the depth and texture of the soil above it, this influences drainage, water availability, root development and nutrient relationships.
The near-complete base saturation recorded in these blocks also describes a very different root environment from that of strongly acidic New Zealand soils. It raises questions that can only be answered through longer observation: how the vines regulate growth in this calcareous setting, how steadily they maintain access to water, and how this physical environment contributes to fruit reaching flavour and phenolic maturity while retaining natural acidity.
The measurements describe the conditions from which the vineyard’s character emerges. Their significance is realised through the terroir as a whole. The relationship between limestone, aspect, climate and vine material influences how the vines grow, how the fruit matures and, ultimately, how the vineyard is expressed in wine.
At Clos Ostler, limestone is the geological foundation of that relationship. Its influence is inseparable from the northern exposure, modest heat accumulation, persistent wind, movement of water and length of the growing season. These conditions act together, forming the particular environment to which the vines respond.
Between inland Otago and the Pacific
The Waitaki occupies a climatic threshold. To the west lie the ranges and the continental interior of Otago. To the east, the valley remains open to the Pacific.
Westerly weather loses much of its moisture while crossing the mountains. Easterly conditions can carry cool air, cloud and maritime influence inland from the coast. Clos Ostler experiences both.
The vineyard’s north-facing slope receives sustained sunlight, while warmth is moderated by latitude, wind and the influence of the Pacific. Spring frost remains a persistent risk. Wind can restrain vegetative growth and contribute to smaller berries. Autumn is often long and cool, allowing ripening to continue gradually while natural acidity is retained.
This extended season is important because grape maturity is not a single measurement. Sugar may accumulate before the skins, seeds, flavours and tannins have reached the completeness we seek. Harvest cannot therefore be determined by sugar or acidity in isolation.
We return to each parcel and taste. We consider the fruit, the resistance of the skins, the maturity of the seeds, the quality of the tannin and the way acidity carries the flavour. The decision is made when these elements converge, recognising that each part of the vineyard arrives there in its own time.
Eight hectares do not ripen as one unit. Small differences in soil depth, exposure, airflow, vine age and planting material become increasingly consequential as harvest approaches.
Learning the vineyard from within
Clos Ostler is planted principally to Pinot Noir, with smaller areas of Chardonnay and Pinot Gris. The Pinot Noir material includes Abel, 667, 777, 115 and UCD6, also known as Pommard.
Each selection behaves differently. Bunch architecture, berry size, vigour, flavour development and tannin maturity vary among them. Their performance also changes according to where they are planted and the conditions of the season.
Abel has a particular place in New Zealand viticultural history through its reported association with material from La Tâche. That history is intriguing, although its value at Clos Ostler must be understood here, through its behaviour in this soil and climate and through what it contributes to the wine.
The same principle applies to every selection. No clone can be understood independently of its parcel. Over a surprisingly short distance, differences in soil depth, exposure and airflow can alter its progression towards maturity. Its role in the final wine may consequently change from one vintage to the next.
Repeated observation has gradually shown us which combinations of parcel and vine material tend to attain the greatest completeness. We preserve these distinctions through harvest, fermentation and maturation. Individual clonal lots are fermented separately in barrel and remain apart during élevage. This gives us time to understand how each component has responded to the season before deciding how the vineyard should be composed.
Some lots reveal themselves quickly. Others appear quiet at first but develop greater depth and persistence as élevage proceeds. Components that seem immediately impressive are not always those that possess the most complete structure. Time is therefore an essential part of selection.
Since 2022, we have worked with tight-grain French oak from Tonnellerie Taransaud, including oak from the Tronçais forest. The proportion of new oak is determined according to the wine and vintage. Cooperage is considered in relation to the structure of each component, allowing its influence to become integrated through élevage and subsequent development in bottle.
The final compositions are made after approximately ten months. By then, the immediate effects of fermentation and oak have begun to settle, and the underlying shape of each component is clearer. There is no fixed recipe. We seek the most complete expression of each variety from the material the season has provided.
Three expressions of Pinot Noir
Caroline’s Pinot Noir is the ensemble. It draws upon the breadth of Clos Ostler, commonly bringing together 115, 667, 777, UCD6 and Abel in a composition determined anew each vintage. Its completeness comes from the relationship between these individual voices. Together, they provide the broadest account of the vineyard and the season.
EOS is the most ageworthy expression of the monopole. It is drawn from the clonal lots that attain prime ripeness while retaining the acidity, tannin quality, depth and persistence required for prolonged development in bottle. These selections are led by 667 and 777, with a smaller contribution from Abel.
The components selected for EOS are determined only after extended tasting during élevage. Concentration is one consideration among several. We look for depth without heaviness, structural authority without hardness, and length that continues after the immediate fruit has passed. The intention is to identify the material with the greatest capacity to unfold over time.
Waitaki Pinot Noir returns to the ensemble with a different emphasis. Its composition is selected for freshness, aromatic lift and clarity of expression. It is released when the available components form a complete wine in this register.
These expressions arise from the same process of separation, tasting and observation. Caroline’s presents the breadth of the monopole. EOS concentrates upon its most enduring structural expression. Waitaki brings forward its freshness and immediacy. Their precise compositions change because the vineyard changes with every season.
Chardonnay and Audrey’s Pinot Gris provide further perspectives on the same escarpment. Their clonal components are also retained separately through barrel fermentation and maturation before blending. Each variety responds differently, but all are shaped by the same interaction of limestone-derived soils, northern exposure, wind and the movement between inland and maritime conditions.
The architecture of an ageworthy wine
Ageing potential is sometimes discussed principally in terms of concentration. Our experience at Clos Ostler suggests something more intricate.
A wine capable of developing for a long period requires fruit of sufficient depth, acidity that remains integral, tannins that are mature and persistent, and a structure in which every element is held in proportion. Its length must already be present within the vineyard material. Extraction can shape structure and oak can support it, but neither can replace the balance established in the fruit.
The cool, extended Waitaki season gives Clos Ostler the opportunity to achieve this alignment. The north-facing escarpment supplies light and exposure, while the surrounding climate restrains the pace of ripening. In successful seasons, flavour and phenolic maturity can progress while natural acidity is preserved.
These conditions also make the vineyard exacting. Frost, wind and delayed maturity create real risk. A prolonged season is valuable only when the fruit reaches completeness before the weather closes in. The potential of the vineyard and its vulnerability arise from the same circumstances.
When the season holds, the resulting wines possess an internal architecture suited to development: natural acidity, fine but persistent tannin, moderate weight and fruit accompanied by savoury complexity. Their balance in youth matters, but their longer measure is what remains after the immediacy of youth has receded.
What continues to return
Across vintages, Clos Ostler Pinot Noir retains natural acidity at full flavour. Its fruit may move from red cherry and plum towards darker tones according to the year, but savoury characters repeatedly accompany it. Dried herbs, earth and spice become more apparent with time in bottle, extending the wine beyond its primary fruit.
These qualities belong to the terroir of Clos Ostler. They arise through the relationship between its limestone-derived soils, climate, exposure and vine material, carried into the wine through the decisions made in the vineyard and cellar. Their recurrence across contrasting seasons is increasingly revealing of the site.
Bottle age provides the longer test. It shows whether acidity remains composed, whether tannins become finer while continuing to support the wine, and whether fruit develops into more complex secondary and tertiary characters while retaining a recognisable centre.
The oldest Clos Ostler vintages now allow this process to be followed over meaningful periods, although the record remains young. More recent wines have yet to complete the development for which they were selected. Longevity is ultimately demonstrated through time in bottle.
Independent assessments provide useful points within that longer record. Caroline’s 2018 received 96 points from Cameron Douglas MS, and Caroline’s 2020 received 97 points from Sam Kim. Caroline’s 2021 was subsequently named Best New Zealand Red Wine, Best New Zealand Pinot Noir and Best North Otago Pinot Noir at the 2025 International Wine Challenge. EOS 2022 received 97 points and Platinum at the 2026 Decanter World Wine Awards, placing it equal among the highest-rated New Zealand Pinot Noirs in that year’s competition.
We value these results as independent observations across several seasons and expressions of the vineyard. Their significance is cumulative. The authority of a site develops as different vintages continue to produce wines of distinction and those wines demonstrate their capacity to evolve.
A vineyard still revealing itself
Clos Ostler remains in the course of being understood. Two decades are sufficient to identify recurring tendencies, but the full character and capability of a vineyard emerge over a much longer period.
The vines continue to mature. Roots explore the soil more extensively. Differences between parcels become clearer. Our understanding of the clonal material continues to deepen, and the wines themselves are beginning to reveal the longer arc of their development.
This is the particular privilege of a monopole. One family can observe a single bounded vineyard over generations, retaining the detail of individual seasons while protecting the identity of the whole. Each vintage becomes part of a continuing record: where maturity arrived first, which parcels retained the greatest freshness, which components possessed the finest tannin, and how those decisions appeared years later in bottle.
The early evidence gives us reason to believe that Clos Ostler can produce Pinot Noir of exceptional quality and longevity. Its limestone geology is rare, its climatic position is exacting, and the recurrence of acidity, savouriness and structural persistence across vintages is increasingly clear. Yet the most interesting questions remain open. How will the vines respond as they enter greater maturity? Which parcels will prove most consistent over several decades? How long can the finest compositions continue to develop?
Those answers cannot be accelerated. They will emerge through the accumulated evidence of seasons and bottles.
Our responsibility is to maintain that record faithfully: to observe carefully, preserve the differences within the vineyard and allow each vintage to express the conditions from which it came.
If Clos Ostler is to become one of New Zealand’s enduring wine estates, that standing will come from the clarity with which it expresses this singular place and from the consistency with which that expression survives time.
For now, the vineyard continues to reveal itself as it always has: slowly, through attention, and through what returns.
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