New RHS UK hardiness system.

[Adrian]

Hard to get a system that means anything, its all down to local conditions and micro climates.
Take Southampton as an example, Bill in town will stay 2 or 3 degrees warmer than me on the outskirts, go 12 miles down the road to portsmouth and they'll get as much as 6 to 8 degrees better protection than I'll have.

Nothing beats trial and error.

[Mr List]

well as it is (was?) the rhs system work in that if a plant was marked as H4 fully hardy, it would be fully hardy no doubts.

other than that it is way out.

[Dave Brown]

well as it is (was?) the rhs system work in that if a plant was marked as H4 fully hardy, it would be fully hardy no doubts.

Even that does not work, as it assumes a healthy plant, grown well. If not healthy, or not grown well. it's hardiness will be reduced.

It is a bit like sticking a healthy person in a cold bath, and sticking someone with pneumonia in a cold bath. The chances of survival could be quite different.

[stephenprudence]

It's up to us, knowledgeable gardeners to choose plants that look like they will perform well. I think these maps serve as an average, but to demand anymore out of a general guide is a little unfair.

obviously people generally know about gardening... in general people to not grow Cycads (in every garden), because they don't see them as hardy, which is a fair point.

[Yorkshire Kris]

Anyway a new system is being introduced.

[flounder]

Doesn't matter who releases what, it won't replace local experience.....oh wait

[billdango]

The sunshine totals for the year for the south coast on that map is way out.

The average mean sunshine hours along the extreme south coast inc the channel islands is between 1.800 and 1.940 hours every year.

The sunshine map shows Southampton at 1.600 hours annually but we get most years between 1.675 to 1.850 hours yearly.

Eastbourne and Jersey get the highest values with Ventnor at 1.910 hours close behind.

rgds billdango

[JoelR]

The met office data is really interesting although not always accurate. The long term rainfall data comes from quite questionable sources the further back you go so the margin for error could be quite high. I know most will agree that the USDA hardiness rating system is of very limited benefit outside the USA so the RHS one is likely to be of more use. My first impressions of it is that it's not very simple to follow. Maybe I'll get used to it....

[Dave Brown]

Maybe I'll get used to it....

I won't get used to it as I don't buy magazines

[Kristen]

A new hardiness system will, be released next year. Full details and an overwintering guide in the latest gw mag.

Means to mention this when you first posted it, but there was an article in the RHS rag "The Garden" in July 2011 discussing what they were thinking about. Presumably this is what GW mag is refering to?

Article was a bit superficial perhaps, but it has since become available on the RHS site:

http://www.rhs.org.uk/Plants/RHS-Public ... s-guidance

[Yorkshire Kris]

A new hardiness system will, be released next year. Full details and an overwintering guide in the latest gw mag.

Means to mention this when you first posted it, but there was an article in the RHS rag "The Garden" in July 2011 discussing what they were thinking about. Presumably this is what GW mag is refering to?

Article was a bit superficial perhaps, but it has since become available on the RHS site:

http://www.rhs.org.uk/Plants/RHS-Public ... s-guidance

Yes this is what the Gardeners Worls article was showing, the new system that has been produced. I think it's a good thing as it will hopefully stop people refering the the US hardiness scheme which is not really relevant to the UK.