Perennial flowers for border

If you want REALLY tall how about Cephalaria Gigantea. Only grows a mere 8 or 9ft here
Maybe there is a taller growing hardy herbaceous plant but I don't know it, tallest I have and that's for certain. Probably @shiney it grows 12 ft with you? Just as an aside Shiney, is your Verbena able to stay out through winter with you? i grow it but have to lift it and keep it in the unheated greenhouse over winter and take cuttings as insurance.

 

I agree that the border looks very narrow. I would widen it. It's nice and long so you can probably have something in flower in every month of the year. That would be my aim.

I'm a big fan of Verbena Bonariensis too as it has such a long flowering period. I have known it start as early as April and go on as late as December depending on how cold it's been. For me in Sussex I loose some in winter but there are always a few that make it through the winter, including this winter which has been cold for us. There are always seedlings though so no need for me to take cuttings.

 

Agree @shiney re verbena I think it's more winter wet that they don't like rather than just it being cold. Mine do self seed but once up and doing don't usually make it throught the winter unless I lift them. Also absolutely agree re Cepharlaria. Superb for giving height, great leaves, not a thug and doesn't need staking which I loath. My particular plants flower are a little more yellow than your photos. Mine flower a sort of Lurpak butter yellow!
I've been selling big chunks of it for £5 which is pretty good value for money when garden centres sell it if you are lucky to find it for £5.99 per 9cm pot.....ie something you could put in your eye! It has huge roots which always seem to break when you dig it up but it doesn't seem to mind, just doesn't grow quite so tall for the 1st year after transplantation.
There are so many great herbaceous plants which aren't readily available so many people don't even know they exist and get stuck with those plants which don't take up much room in the garden centres!

 

@silu interesting that you should say that. Those are usually a lemon yellow here. I wonder if the colour changes due to the climate being colder?

 

Maybe @Sandy Ground or it's got to do with the PH perhaps.

 

Thanks @shiney, mine is sort of like this, you live and learn. Whatever they are all so pretty, one of my favourites.

 

Between the gaps in the Sedumns, I'd plant a few perennials that flower at different times of the year so that there's always a splash of colour.

@wiseowl - what is the flowering period of your Sedums?

 

One of the Bi Product of Sedum, is when you cut back the old dry stuff it makes great Kindling for a log burner, and sounds fun as cracks. The Ash makes good compost when applied to the Garden, or added in your Compost.