By Sto391
County Durham,
United Kingdom 
I have some Primroses in garden which I planted 6 years ago.I planted 4 yellow and 2 rose coloured.The first 2 year - the same 6 plants.Since then I've now got about 20 or so.I'm guessing they've self seeded. However, the strangest has happened every year.Sometimes I get more yellow than pink and vice versa.Only last year they were all yellow.Wonder what they will be this year ? Does anyone know why this happens ? Mind I'm not complaining.
22 Jan, 2010
Answers
Thanks for the response.Its had me stumped and never thought.At least there will be interest each year.
23 Jan, 2010
Previous question
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They revert, Sto391 - and also get pollinated by insects- so they are cross-pollinated with native primroses as well as with each other.. With these factors, and the fact that they don't come true to the parent plant from seed anyway - you have a mixture there - and they will alter each year, too! :-))
22 Jan, 2010