Thanks very much, that's really helpful. A lot of things I hadn't considered.

I already have verbena bonariensis and sedums, both of which are fantastic. My baby cardoons got a bit too dry last summer and died, but I'll grow some more this year. They do look pretty impressive.

Your suggestion of chopping back to prolong flowering and avoid staking sounds good. I read an article about it a couple of years ago, but I haven't actually tried it yet.

ladies mantle (mollis) is a good low growing plant for the front of a border and have beautiful pal green flowers and crocosima are good strong plants for fillin gaps and have a strappy structural effect good luck

I have a large pink polygonum that has good foliage - large leaves, makes a lush, satisfying clump, with pale pink bottlebrush flowers in May. Doesn't like drought, however.

I would also recommend hostas, especially the large, variegated-leaf ones like Frances Williams. OK, I know they're a bit eighties, but I still think a good big clump is stunning.

Helianthus like "Lemon Queen" do a great job of adding height to my borders, and flower profusely for a month in late summer. They are slightly more than "gently spreading" but I go round the clumps each spring culling surplus shoots and this controls them well.
I find they don't need staking despite being 4' tall.

Geranium phaeum is great for shadier spots. Geranium canariense/maderense is absolutely fab - large, evergreen, beautiful feathery foliage, good pink flowers, self-seeds but easy to remove - what more could one ask of a plant? Geraniums are OK in general but need a good scalping after flowering to prevent them looking rank and overgrown in late summer.

A bit wild, but I like Lythrum salicaria for both height and colour in late summer. Supposedly needs boggy ground but certainly doesn't get it in my garden.

Sedums - lovely plants, and very adaptable.

Gladioli byzantinus - gorgeous colour & just about to flower :-) but I do find the foliage a bit of a pain. Because they're tallish it's not easy to mask the foliage and also it flops about everywhere before they have flowered. A very prolific propagator, this is now popping up everywhere in my garden. Because it's so lovely I've left it to it's own devices, however. Easy enough to dig up clumps or tear off the foliage if I get fed up with it!

I have found asters to be excessively invasive but may be worth it for the "Spring in Autumn" effect. "Sailor Boy" is an excellent fluorescent blue.

Physocarpus "Diablo" and to a lesser extent, the yellow version are good foliage workhorses. Just prune them hard. Also the red/purple Cotinus - fantastic foliage when pruned hard.

Just a thought, but Rozanne isn't "well-behaved", it is floppy and trailing. It is best wedged between a couple of dense shrubs for that "push-up bra" effect ;)

G. x. magnificum is a much better self-contained mound, more spectacular in flower, but only for a few weeks in spring.

Lavender? Daylilies? Hostas? Astilbe? Fuchsias?

For real height, Nicotiana sylvestris, but really only good as an annual. Foxgloves, similar problem and a short flowering period. Both will reseed. Various lilies in various heights, all the way to Cardiocrinum.

Heh, heh, push-up bra, indeed! Some people's minds!

Hardy figs are a must - needing little pruning or attention but cropping well if given some sun. Easy from cuttings as well.

best regards

Chris

Have you thought about Penstemons, there are some lovely variations, if the flowers are cut off instead of been allowed to go to seed they just keep on flowering well into late Autumn.
In the spring just cut down to about 6" above ground & off you go again.

Wot, no-one mentioned Physostegia virginiana yet?

;-)