Knollbirne

How it is classified

What it contributes to a blend

A direction, not a measurement. These bands are the level of resolution the evidence supports, and they say which way adding this fruit pushes a blend rather than what the finished cider will be.

Ferociously tannic as fruit and moderate as Most, with the difference made entirely by how long it was stored.

Aroma

No aroma descriptors are recorded for Knollbirne, and for a great deal of cider fruit that is a finding rather than a gap. Bittersweet apples in particular contribute tannin, sugar and body while being close to aromatically mute, and most of what a cider made from them smells of was produced by the fermentation rather than carried in by the fruit. CiderHQ publishes the absence rather than filling the space with descriptors nothing supports.

Put Knollbirne into a blend

Measured analysis

Each figure is shown with where and when it was taken. They are not averaged: the same cultivar grown in another climate genuinely gives different numbers, and collapsing them into one would be the most misleading thing this page could do.

Compare within a study to see where these figures sat among the other cultivars the same work analysed — which is a more robust statement than the figures themselves, because absolute values move between laboratories and the ordering inside one study mostly survives.

Watched in the orchard

What named research programmes recorded about this fruit at their own sites. Bloom, harvest and cropping belong to a place and a run of seasons rather than to a cultivar, so they are reported site by site rather than merged.

In the orchard

Harvest window

Mid

Flowering

Not recorded

Vigour

Vigorous

Cropping

Slightly biennial

Keeping

Poor — mill soon after picking

Picked in mid September at Klosterneuburg and pressed in late October, after around five weeks. The ministry gives a ripening window of October into early November.

Not recorded. Austrian sources do not publish flowering groups or bands for Mostbirnen in any form CiderHQ has reached.

Juice and pressing

• 2 860 to 4 050 mg/L total phenols at harvest, falling to 130 by pressing
• 7.1 per cent alcohol in the must
• 6.1 g/L acid as tartaric
• Only 2.4 g/L malic acid, the lowest in the trial

How it is used

• Described by the standard Austrian pomology as well suited to single-variety Most.

On its own

About Knollbirne

Names, origin and identity

Cultivar naming is the hardest problem in cider fruit data. The same tree carries different names across ten miles, and two different trees have shared a name for two centuries.

Why it matters

• The steepest documented phenolic collapse in storage of any fruit on this site: 4 050 mg/L down to 130.

Related cultivars

Recorded relationships, including the ones this fruit is routinely confused with.

• Similar role

  Grüne Pichelbirne

  The other variety whose harvest phenolics collapse almost entirely in store.

Fruit that plays a similar part

Cultivars sharing a classification under the same system and a comparable role in a blend. Not a similarity score — a stated relationship.

• Tumper

  A very early Three Counties perry pear whose juice contains almost no nitrogen a yeast can use, and more proline than any other variety measured.

• Ducksbarn

  A low-acid Three Counties perry pear whose juice carries the second-highest proline figure in the modern survey — abundant amino acid that yeast cannot use.

• Gin

  A small Herefordshire perry pear named, like Brandy and Sack, for the strength of the drink it makes rather than for anything about the fruit.

• Luxemburger Mostbirne

  An Austrian Most pear the standard pomology calls notably tannin-rich, whose measured phenolics are middling and whose chlorogenic acid is nearly the lowest in the trial.

• Barland

  One of the oldest named English perry pears, associated with Bosbury in Herefordshire and recorded in seventeenth-century writing, giving a markedly tannic perry that was once famous by name.

• Plant de Blanc

  The dominant poiré pear of the Domfrontais and the cultivar the Poiré Domfront appellation is built around.

Where it grows

• Mostviertel
• Upper Austria

What people ask next

Questions readers ask about the things this page mentions. Each one goes to the section that answers it rather than to a page written to receive the question.

• What is perry — Perry is an alcoholic drink made by fermenting the juice of pears, traditionally of specific perry pear cultivars rather than eating pears. It is to pears what cider is to apples, and has its own history in the three counties of England and in Normandy.
• How long can apples be kept before pressing
• What does sweating apples mean — Sweating is holding picked fruit in a heap or store for days or weeks before milling, so it softens, loses water and gains sugar concentration. Perry pears in particular are usually held until they yield to the thumb.
• What is juice blending
• Which perry pear is the sharpest — Of the Austrian varieties measured at Klosterneuburg, Grüne Pichelbirne — an Upper Austrian pear first recorded in 1822, whose must the trial found sharpest of the set and among the most phenolic. Its acid is reported as tartaric, so it is not directly comparable with English figures.
• Is most made outside the mostviertel — Yes. Upper Austria carries the same pear and apple Most tradition as the Mostviertel next door, on a large orchard base, and the boundary between them is administrative rather than cultural.

Where to go next

• How cider apples are classified — Why there are four schemes and none of them is universal.
• The blend explorer — See which way changing the proportions moves a blend.
• Blending — What a cider maker is actually deciding when they build a blend.

Sources

What this page rests on. Where a source is marked as registered rather than read, CiderHQ is recording that the body is authoritative on the subject without claiming to have worked through the document itself. See our evidence policy for what each state means.

• Prüfung ausgewählter Mostbirnensorten als Spindel unter Bio-Produktionsbedingungen

  Wurm, Gössinger, Wendelin and Korntheuer, HBLA und Bundesamt für Wein- und Obstbau Klosterneuburg, in Mitteilungen Klosterneuburg 61 (2011): 236–246 · research institute · passage verified 2026-08-25 · covers 2002–2010

  Fourteen Austrian perry pears trialled at the research station that also runs Austria’s statutory fruit-wine analysis panel. The only measured Austrian Mostbirnen data CiderHQ has found, and the first Austrian figures on the site. Its tables are scanned images with no text layer, so every figure published here was read from the rendered pages directly rather than from an extraction, and the source’s own typesetting error — Knollbirne’s residual sugar printed “3,o” — is recorded rather than normalised. The acid convention is tartaric rather than malic, which is Austrian wine law and is stated on every measurement taken from it.

• Österreichische Mostbirnensorten

  Bundesministerium für Land- und Forstwirtschaft, Klima- und Umweltschutz, Regionen und Wasserwirtschaft (BMLUK), register of traditional Austrian foods, entry 191 · government · retrieved 2026-08-25

  The Austrian agriculture ministry’s own account of its perry pears, in its register of traditional foods. It carries no analytical figures at all — no acid, no sugar, no tannin — and is cited here for synonymy, geography, dates and the ministry’s own descriptions of what the fruit tastes like. Its estimate of over 400 Mostbirne types in Austria is labelled by the ministry itself as an estimate, and CiderHQ repeats that hedge rather than the number alone.

• Obstweinverordnung, BGBl. II Nr. 18/2014, consolidated

  Republic of Austria, made under §§ 35, 36 and 37(1) of the Weingesetz 2009; consolidated text published by the Bundeskellereiinspektion · legislation · passage verified 2026-08-25

  The instrument that decides what Most legally is in Austria, and the answer is: a fermented drink. That single fact is the one most often got wrong in English writing, because Most means the unfermented juice in Switzerland and is ambiguous in Germany. The ordinance also names two pear cultivars individually — Speckbirne and Schweizer Wasserbirne — in a derogation lowering their minimum acidity, which is a legislature encoding pomology. Retrieved from the federal cellar inspectorate’s mirror because the Austrian legal information system refused every automated request.