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RHS Hardiness RatingsI've noticed something strange has happened to the RHS hardiness ratings - first


By Bamboo

London, United Kingdom Gb

RHS Hardiness Ratings

I've noticed something strange has happened to the RHS hardiness ratings - first, Verbena bonariensis is now listed as fully hardy in the UK, when it didn't used to be. Today, I looked up Pennisetum setaceum on the RHS site. The description says its usually grown as an annual in the UK, and needs winter protection - yet the Hardiness rating is 6, which equates to 'hardy throughout all of Europe and the UK (down to -20deg C)', which it certainly isn't, so far as I know. Anyone else noticed these anomalies, or is it that they've changed their ratings (but not their descriptions) because of global warming? Or some other reason...or is it just plain wrong?



Have a look here:
It explains the hardiness ratings.

6 Sep, 2015


Well thanks for the link landgirl, but I know they've altered their hardiness ratings, making them narrower but with more categories - but it does not explain why a plant thats described as needing winter protection is rated as H6, hardy down to -20 degC. It would appear the rating of H6 has been misapplied, is my point....

I have actually emailed them regarding this, so I'll be interested to see how they explain it...

6 Sep, 2015


I'd be interested too Bamboo, I rely on such info as I need bone hardy plants here

7 Sep, 2015


Yea, Pam, I'll post whatever I find out here on this thread, so you'll see it anyway

7 Sep, 2015


Thanks ☺

7 Sep, 2015

How do I say thanks?

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