Cider apple
Skyrme’s Kernel
A Herefordshire bittersharp with high acid and firm tannin, one of the county’s few genuine vintage-quality cider apples.
Also written Skyrmes Kernel, Skyrme’s Kernal, Skyrmes.
- Classification
- Bittersharp — Long Ashton classification
- Harvest
- Mid (Late September to mid October)
- Single varietal
- Sometimes bottled on its own
- Blend role
- Vintage quality, Acid lift, Tannin and structure, Aroma
- Origin
- Herefordshire
- Species
- Malus domestica
- Vigour
- Moderate
- Biennial bearing
- Markedly biennial — heavy and light years alternate
- Keeping
- Moderate
- Evidence
- Analysed in 1 source, watched at 1 trial site
How it is classified
Long Ashton classification
Bittersharp
High acid and high tannin together — the rarest and, for a single-varietal cider, the most useful class.
Basis: Above about 0.45% w/v acid and above about 0.2% w/v tannin.
A bittersharp: acid and tannin both above the scheme’s thresholds. The placement is well supported by description; no verified per-cultivar analysis is attached.
Every classification on CiderHQ names its system. Why there is more than one.
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 drink will be.
| Axis | Typical | Range |
|---|---|---|
| Acid | High | |
| Tannin | Firm | |
| Sugar | High | |
| Bitterness | Moderate | |
| Astringency | Noticeable | |
| Aroma | Pronounced | |
| Body | Full |
The bittersharp classification plus consistent description of a fruit capable of making cider on its own.
Carries acid, tannin and aroma together, which is the combination that makes a bittersharp worth growing.
Aroma
No aroma descriptors are recorded for Skyrme’s Kernel, 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.
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.
Measured on the fruit
Measured on the fruit itself, before anything was done to it. These figures hold whatever was later made from the juice.
| Property | Reading | Where | When | Source |
|---|---|---|---|---|
| Fruit diameter | 61 mm (56–65) | USDA-ARS Plant Genetic Resources Unit, Geneva, New York, USA | 2017Modern analysis | Cornell University / USDA-ARS Plant Genetic Resources Unit |
| Fruit firmness | 50.0 N (39.0–61.0) | USDA-ARS Plant Genetic Resources Unit, Geneva, New York, USA | 2017Modern analysis | Cornell University / USDA-ARS Plant Genetic Resources Unit |
| Fruit weight | 100 g (81–119) | USDA-ARS Plant Genetic Resources Unit, Geneva, New York, USA | 2017Modern analysis | Cornell University / USDA-ARS Plant Genetic Resources Unit |
| Starch pattern index | 7.1 SPI (6.6–7.5) | USDA-ARS Plant Genetic Resources Unit, Geneva, New York, USA | 2017Modern analysis | Cornell University / USDA-ARS Plant Genetic Resources Unit |
Measured on the juice
Measured on juice as pressed, before fermentation. This is where most cider analysis lives and what the classification schemes are defined on.
| Property | Reading | Where | When | Source |
|---|---|---|---|---|
| Brix | 13.0 °Bx (9.8–16.2) | USDA-ARS Plant Genetic Resources Unit, Geneva, New York, USA | 2017Modern analysis | Cornell University / USDA-ARS Plant Genetic Resources Unit |
| Fructose | 68.2 g/L (61.0–75.4)Not used in comparisons: see note below | USDA-ARS Plant Genetic Resources Unit, Geneva, New York, USA | 2017Modern analysis | Cornell University / USDA-ARS Plant Genetic Resources Unit |
| Glucose | 15.8 g/L (14.4–17.2)Not used in comparisons: see note below | USDA-ARS Plant Genetic Resources Unit, Geneva, New York, USA | 2017Modern analysis | Cornell University / USDA-ARS Plant Genetic Resources Unit |
| pH | 3.46 pH (3.36–3.56) | USDA-ARS Plant Genetic Resources Unit, Geneva, New York, USA | 2017Modern analysis | Cornell University / USDA-ARS Plant Genetic Resources Unit |
| Sorbitol | 11.2 g/L (9.4–13.0)Not used in comparisons: see note below | USDA-ARS Plant Genetic Resources Unit, Geneva, New York, USA | 2017Modern analysis | Cornell University / USDA-ARS Plant Genetic Resources Unit |
| Sucrose | 43.7 g/L (33.9–53.5)Not used in comparisons: see note below | USDA-ARS Plant Genetic Resources Unit, Geneva, New York, USA | 2017Modern analysis | Cornell University / USDA-ARS Plant Genetic Resources Unit |
| Titratable acidity | 5.4 g/L (4.8–6.0) | USDA-ARS Plant Genetic Resources Unit, Geneva, New York, USA | 2017Modern analysis | Cornell University / USDA-ARS Plant Genetic Resources Unit |
| Total phenolics | 1570.0 mg/L (1270.0–1870.0) | USDA-ARS Plant Genetic Resources Unit, Geneva, New York, USA | 2017Modern analysis | Cornell University / USDA-ARS Plant Genetic Resources Unit |
How these were measured
- Mean of the fruit sampled per accession; where a bracket is shown it is one standard deviation either side of the mean, not the observed range. Published to two decimal places and shown at the precision CiderHQ displays for the unit.
- Mean of the fruit sampled per accession; where a bracket is shown it is one standard deviation either side of the mean, not the observed range.
- Cornell generic starch–iodine chart, 1–8, where 1 is no hydrolysis and 8 is complete. Mean of replicate fruit; a bracket, where shown, is one standard deviation either side of it.
- Penetrometer, mean of replicate fruit; a bracket, where shown, is one standard deviation either side of the mean.
- Refractometer on pressed juice. Mean of replicates; a bracket, where shown, is one standard deviation either side of the mean.
- Titration to pH 8.1 with sodium hydroxide, reported as malic acid equivalents. Mean of replicates; a bracket, where shown, is one standard deviation either side of the mean.
- The starting pH recorded by the autotitrator before titration, on juice stored frozen at −80 °C and thawed; the source describes no separate pH measurement. Mean of replicates; a bracket, where shown, is one standard deviation either side of the mean.
- Folin–Ciocalteu assay against gallic acid standards, published in grams per litre of gallic acid equivalent and stored here as milligrams per litre by exact conversion. The source converts these figures to Löwenthal tannic acid equivalents, by a laboratory factor of 1.6, only to sort its accessions into classes; the figure here is the unconverted one.
- Enzymatic assay (Megazyme). Mean of replicates; a bracket, where shown, is one standard deviation either side of the mean.
- D-sorbitol/xylitol assay kit (Megazyme), sorbitol dehydrogenase method. Mean of replicates; a bracket, where shown, is one standard deviation either side of the mean.
- Glucose, fructose, sucrose and sorbitol: Not used in any distribution, ranking or comparison. This programme’s enzyme-assayed sugars do not reconcile with its own refractometer readings across the collection — for many varieties the sugars add up to more than the Brix reading allows. The figures were checked against the thesis’s own tables in October 2026 and are transcribed exactly: the disagreement is in the published source, which does not say which reading is wrong. Proportions between glucose, fructose and sucrose, which came from one assay, are still used in summary.
- A chart position, not a quantity. Almost every accession here scored at or near 8, which says the fruit was picked at or past full starch conversion rather than that the cultivars are alike.
- One harvest at one site. Soluble solids move several degrees between seasons and with crop load.
- A Folin–Ciocalteu figure counts everything that reduces the reagent, not tannin alone, and is not interchangeable with a Löwenthal permanganate figure for the same juice. Compare this reading with other Folin–Ciocalteu readings in gallic acid equivalents.
Where it sits among the varieties each programme measured
| Programme | Property | Skyrme’s Kernel | Programme median | Position |
|---|---|---|---|---|
| The USDA-PGRU germplasm characterisation | Titratable acidity as malic | 5.4 g/L | 4.1 g/L | Above 36, level with 2, below 8 of the other 46: highest quarter |
| The USDA-PGRU germplasm characterisation | pH | 3.46 | 3.64 | Above 9 and below 31 of the other 40: lowest quarter |
| The USDA-PGRU germplasm characterisation | Total phenolics | 1570 mg/L | 980 mg/L | Above 31 and below 15 of the other 46: upper middle |
| The USDA-PGRU germplasm characterisation | Brix | 13.0 °Bx | 12.5 °Bx | Above 30, level with 1, below 15 of the other 46: upper middle |
| The USDA-PGRU germplasm characterisation | Fruit diameter | 61.0 mm | 65.0 mm | Above 14, level with 1, below 31 of the other 46: lower middle |
| The USDA-PGRU germplasm characterisation | Fruit weight | 100 g | 124 g | Above 12, level with 1, below 33 of the other 46: lower middle |
| The USDA-PGRU germplasm characterisation | Fruit firmness | 50.0 N | 58.9 N | Above 9 and below 35 of the other 44: lowest quarter |
| The USDA-PGRU germplasm characterisation | Starch pattern index | 7.1 SPI | 8.0 SPI | Above 5, level with 2, below 37 of the other 44: lowest quarter |
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.
USDA-PGRU Malus germplasm characterisation
USDA-ARS Plant Genetic Resources Unit, Geneva, New York, in the Finger Lakes region of western New York State · 2017 · Cornell University / USDA-ARS Plant Genetic Resources Unit
Humid continental, with cold winters and warm summers moderated by the Finger Lakes — a sharper seasonal swing than any of the European cider regions whose fruit the collection holds, and warm enough in late summer to bring acid down faster than a maritime autumn does.
- Held as
- PI 161846, held as “Skyrme’s Kernel”
One harvest season. Fruit assessed for weight, diameter, starch pattern index on the Cornell 1–8 chart and flesh firmness by penetrometer; juice pressed and measured for soluble solids by refractometer, titratable acidity by titration to pH 8.1 as malic acid, pH as the autotitrator’s starting reading on juice that had been frozen, total phenolics by Folin–Ciocalteu assay as gallic acid equivalent, and glucose, fructose, sucrose and sorbitol by enzymatic assay.
In the orchard
- Harvest window
- Mid
- Flowering
- Not recorded
- Vigour
- Moderate
- Cropping
- Markedly biennial — heavy and light years alternate
- Keeping
- Moderate
October.
A light and irregular cropper, as most bittersharps are.
Mid to late flowering. No pollination group is recorded.
Disease and pest susceptibility
| Issue | Susceptibility | Note |
|---|---|---|
| Scab | moderate | — |
| Canker | moderate | — |
Juice and pressing
- High acid
- Firm tannin
- Good sugar
- Aromatic
How it is used
- A vintage-quality Herefordshire cider apple
- Used in small proportion to lift and structure bittersweet blends
On its own
Sometimes bottled on its own
Made as a varietal by a small number of Herefordshire producers, and it works: the fruit carries enough of everything. It is not as established in that role as Kingston Black, and there is far less of it.
About Skyrme’s Kernel
Herefordshire has never had many bittersharps. The county’s cider tradition was built on bittersweets — the Normans, the Michelins, Brown Snout — with acid brought in from Foxwhelp or from culinary fruit. Skyrme’s Kernel is one of the exceptions: a Herefordshire seedling carrying acid, tannin and aroma in one apple, and therefore capable of making a complete cider without help.
It has never been planted in quantity, for the usual reason: bittersharps crop lightly and irregularly, and a commercial orchard cannot be built on them. It survives in small plantings and in the hands of producers who want a county alternative to Kingston Black, and the ciders made from it support the reputation.
The name is worth reading carefully. "Kernel" means the tree came from a pip rather than a graft, which places it among the chance seedlings that make up almost the whole English repertoire; "Skyrme" is a Herefordshire surname and locates the family, not the orchard. As origin evidence goes, that is more than most cultivars in this file offer and still not much.
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.
Origin · traditional account
Named for a Herefordshire family. "Kernel" in English fruit naming indicates a seedling — a tree raised from a pip — which is the one substantive thing the name records.
Related cultivars
Recorded relationships, including the ones this fruit is routinely confused with.
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.
Kingston Black
The most celebrated English single-varietal cider apple: a small dark-red bittersharp carrying acid and tannin in one fruit, and a tree difficult enough that its reputation has always outrun its plantings.
Hewe’s Crab
The historic cider crab of Virginia — small, hard, very high in acid and unusually tannic for an American apple, and probably a hybrid between a cultivated apple and a native crab.
Foxwhelp
The oldest named English cider apple still grown, a Herefordshire bittersharp of extraordinary acidity whose identity has fractured into a family of sports, seedlings and impostors.
Stoke Red
A small, dense, dark-red Somerset bittersharp carrying both high acid and substantial tannin, and the most reliable alternative to Kingston Black for a single-varietal cider.
Broxwood Foxwhelp
A Herefordshire selection of Foxwhelp from Broxwood, keeping much of the parent’s acidity in a fruit that is easier to grow, and the form most commonly planted today.
Frederick
A Monmouthshire bittersharp with bright red-striped fruit and high acid, the most widely known of the Welsh border cider apples and a genuine single-varietal candidate.
Where it grows
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 kingston black — Kingston Black is a Somerset bittersharp with an unusual balance of acid and tannin, long regarded as capable of making a complete cider unblended. It is difficult to grow well, which is why it is scarcer than its reputation suggests.
- How do i balance acid and tannin in a blend — Acid and tannin do different jobs and cannot substitute for each other: acid gives freshness and microbiological safety, tannin gives structure and length. A blend short of acid tastes flabby however tannic it is.
- How do you blend cider
- Is single variety cider better than a blend — Neither is inherently better and CiderHQ does not rank them. A single varietal shows one cultivar’s character and depends entirely on that fruit being balanced; a blend is how most makers reach balance deliberately.
- What are the three counties in cider — Herefordshire, Gloucestershire and Worcestershire — the block of country where England’s cider and, above all, its perry have historically concentrated.
- What is foxwhelp
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.
A Somerset Pomona: The Cider Apples of Somerset
Liz Copas, The Dovecote Press, 2001. ISBN 9781874336877 · reference work · bibliographic record verified, not opened 2026-08-25
Bibliographic record verified on 2026-08-25 against Open Library: Liz Copas, The Dovecote Press, 2001, ISBN 9781874336877. The author was Long Ashton’s cider pomologist, which is why this work is registered for Somerset cultivar identity at all — it is the nearest thing to a successor to the station’s own descriptions. No copy was opened. Not digitised in any open collection.
University of Reading / Defra, Brogdale · research institute · retrieved 2026-08-24
The UK national reference collection for apple and pear cultivars. The authority CiderHQ uses for whether two names are the same fruit, which is the central duplicate-resolution problem in cider data.
Three Counties Cider and Perry Association
TCCPA · specialist organisation · retrieved 2026-08-24
Research Evidence standard for this record. What that means.