Correction to my previous posting on this subject: the website I identified is not www.shoot.com, it is www.shootgardening.co.uk.

Sorry for any confusion!

Since this is such a vast country with a great many different climates and growing conditions - 11 different hardiness zones - I doubt you will find a database that will satisfactorily address what to do when uniformly for all areas. For example, the timing on when to prune roses will differ dramatically depending on whether you are located in California, Connecticut or Arkansas. Some plants will require winter protection in certain areas but be perfectly happy in winter conditions elsewhere. Same thing for lawn care - cool season turf grasses require different maintenance approaches than do warm season grasses common to the more southern areas.

Lots of designers, myself included, prepare maintenance schedules of varying complexity as part of the design package for clients that may require them. It is pretty easy to construct a simple database yourself based on your typical plant palette or month by month. And for the west coast, Sunset magazine has a monthly garden checklist included with every issue that is quite helpful. Since this publication is tailored by region, a subscription will assure the clients get the correct info for their location.

I agree with your insights about regional climate differences, and as a Sunset magazine subscriber, I can attest to its helpfulness in planning for garden maintenance.

But since I have thousands of plants at my disposal in designing a client's garden, I am hopeful there is a regional resource which could help. My experience is limited to those I have grown in my own garden. Advice, though, from outside sources such as Sunset is easy to come by.

The website I mentioned, shootgardening.com, seems to be the best fit for such tailored advice since the regional climates between England and Portland are similar enough.

Perhaps I should include a subscription to Sunset as a value-added service to my clients!

Portland has a hotter summer that will not equate to most or all of Britain. In a given year spring-flowering trees down there (Sunset 6) are often two weeks ahead of the same kinds here in Greater Seattle (Sunset 5). So, even within this region there are significant differences.

The British Isles contain more than one climate also, maps show a range of hardiness zones extending all the way from 7 to 11. This is due to the Gulf Stream producing Californian conditions on the west coast, grading down to the colder hilly areas in the interior and north.