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What characteristics have you used to exclude Betula pubescens - Downy Birch?
Thanks for help!
I've been interested in the differences between UK birch species for a few years, and I now suspect that divisions between pubescens and pendular are increasingly blurred. Genetically, downy birch is said to have 56 chromosomes (tetraploid) while silver has 28 (diploid). According to some studies true hybrids (42 chromosomes) are surprisingly rare, but tetraploid trees often display a wide range of native birch characteristics, from "pure" downy to "pure" silver. This is tentatively believed to be the result of the back-crossing process called introgression
According to a user on this site, AlanS, another similar species, betula celtiberica - usually said to be native to the Iberian Peninsula - is now considered native in some parts of the UK, and I've recently read an article that suggests celtiberica is native in Wales.
Trees don't read books and they don't always fit into the human boxes we like to build for them. Even among nursery silver birch, bred for their pendula characteristics, you'll sometimes find the odd hairy interloper. Though this is confusing too, because some authorities say hairiness can be a juvenile characteristic of pendula.
Lat/Lng: 51.619553, -0.11651
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Broomfield Park, Palmers Green