Glossary · Orchard
Self-incompatible
Also written self-sterile. Each is a name for the same thing, which is why none of them has an entry of its own.
Definition
Unable to set a useful crop from its own pollen. Almost all apples and pears are self-incompatible, so an orchard needs at least two cultivars flowering together.
- Subject
- Orchard
- Also written
- self-sterile
In more detail
Incompatibility is controlled by S-alleles: pollen carrying an allele the recipient flower also carries is rejected before fertilisation. Cultivars sharing both alleles — often because one arose as a sport of the other — cannot pollinate each other, which is why compatibility tables list more than flowering time.
Where this is covered properly
The glossary defines; these pages explain. Each is described in its own words.
Related terms
Terms that belong to the same part of the subject, or that this one is routinely confused with.
Orchard
Pollination group
A numbered band grouping cultivars by the timing of their blossom, so that a grower can plant varieties that flower together and can therefore pollinate one another.
Orchard
Triploid
A cultivar carrying three sets of chromosomes rather than two. Triploids are vigorous and often heavy croppers but produce sterile or near-sterile pollen, so they cannot pollinate anything and need two other cultivars in the orchard.
Orchard
Pollinator
A cultivar planted to supply compatible pollen to the cropping variety, or — in the other sense of the word — the insect that carries it. Crab apples are often used as pollen sources because they flower long and heavily.
Fruit
Sport
A shoot that differs genetically from the rest of the tree through a somatic mutation, and which can be propagated as a new cultivar. Many red-skinned strains of familiar apples arose this way.
Where to go next
- Cider glossary — The whole vocabulary, by subject and A–Z.
- Comparisons — Terms that are only really clear when set against the thing they are not.
- Search — Finds terms by their aliases and by their spellings in other languages.
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.
NIAB (incorporating East Malling Research)
NIAB · research institute · retrieved 2026-08-24
East Malling developed the M-series apple rootstocks that determine tree size in essentially every modern orchard, cider orchards included. The authority CiderHQ uses for rootstock behaviour.