Holy wow. This is a great rabbithole.
'Bramble has the remarkable ability to produce its seeds without being fertilised.
This happens when the plant’s pollen gets on its flower's own stigma, stimulating fruit formation without fertilisation actually occurring.[13]
This form of reproduction is neither asexual or sexual. It's called ‘apomixis.’ Dandelions do it too. The seed is genetically identical to the parent.[14]
On those occasions when a bramble reproduces sexually, a different strain of the species can sometimes establish itself, developing and multiplying rapidly through the power of apomixis.[15]
Bramble Seeds
[Source: Flickr Creative Commons © Joanna Paterson]
And here's another thing - some bramble plants are also "polyploid," meaning their chromosomes have doubled or trebled in number.[16]
Together, the phenomena of apomixis and polyploidy have caused the bramble to split into many microspecies. The bramble is therefore not actually one species, it's an ‘aggregate’ species.[17] In fact the bramble is split into 320+ microspecies scattered across the British Isles.[18]