"No Phlox paniculata-hybrids cause it is to hot for them"

But you say it only gets to about 77 degrees in summer! Definitely not too hot for phlox, which thrives in the US in much hotter temps.

Have you considered any of these:

Iris sibirica/Siberian iris
Verbascum/mullein
Baptisia australis/false indigo
Platycodon/balloon flower
Liatris spicata/gayfeather
Lobelia cardinalis/cardinal flower
Penstemon digitalis/beardtongue
Ratibida columnifera/Mexican hat
Trollius ledebouri/globeflower

I have all of the above growing in full sun as well as part sun. My soil is sandy loam & slightly acidic. I wouldn't rule out Pennisetum alopecuroides 'Hameln'/dwarf fountain grass for textural contrast. I have Gaura lindheimeri/wandflower growing as well. It flops over but is so beautiful the bees & I don't mind.

Chelone - Hot Lips or one of the species
shrub roses
Japanese or Louisiana Iris
Lobelia siphilitica if you can keep it deadheaded to prevent reseeding
tall daylilies in the raspberry, pink, or lavender range
Purple loosestrife (Lythrum salicaria) is listed as native to Switzerland; does it get used as a garden plant?
Peonies

What about Lilies? I have loamy clay that is leaning toward the heavy side and Perovskias flop for me and well draining perennials don't like me much, but I've grown Lilies in my full sun bed and they seem happy as clams.

We have the issue of red lily leaf beetles here, not sure if you do there.

In my experience, Penstemons have been short lived but sometimes reseed.

Heliopsis in this same location for me grew to almost 5ft.

Grasses

What about Buddleia or Low Care Roses mixed in with the perennials?

How about some the American native prairie plants which thrive in heavy soil and hot sun:
Eupatorium 'Gateway'
Echinacea purpurea (coneflower)
Liatris spicata (blazing star)
Allium cernuum (nodding onion)
Physostegia virginiana (obedient plant) 'Vareigata'
Asclepias incarnata (swamp milkweek)

Rudbeckia, Rudbeckia, oh and Rudbeckia! Perfect for those conditions, blooming machine and care-free.

Our area is heavy clay, to which we frequently add organic matter.

We get a lot of the herbaceous perennial height in our garden from tall garden phlox and tall heleniums, but they don't like dry conditions (former, as you say).

We also get a lot of height from monkshood and New England asters and smaller amounts from perennials like, an old (species?) globe thistle, false sunflower and Kashmir tree mallow.

I also love culver's root ('Fascination' in the picture below). The purple loosestrife is 'Rosy Gem'. I use purple loosestrife, but only very carefully.

Picture July 22, 2013:

This post was edited by SunnyBorders on Tue, Mar 25, 14 at 17:29

thanks folks,
that is great, some food for thought, I am going to do research on the suggested plants.

Sorry, mistook the temperatures, got confused by Fahrenheit,
temps are around 90 in August

I tried Phlox in another patch, did not thrive,
but I think because it had a rough start, frost heaving in first winter, not enough water in first summer,

they look quite good now (year 3), so probably some more TLC should solve this problem.

Liatris sounds great

definetely a smallish shrub rose/ modern, hardy rose

perhaps globe thistle /Echinops?

the rest I really need to look up, some stuff I haven`t heard of yet.

The Lythrum/ loosestrife is too strong or weedy.

Ponder grasses, Penniestum is really good,

Thanks again, I will post my shortened list of choice,

have a great week, bye, Lin

Lin, I purposely listed Pennisetum/fountain grass for the textural contrast it offers. I added it to my perennial bed on the southeast side of my garden in front of a Harry Lauder Walkingstick/demented witch hazel tree since the textural contrast is so amazing. Also, because it's a dwarf ornamental grass that grows just 2-3 ft. tall (rather than the Miscanthus that grows 8 ft. tall) and it has an elegant, graceful arching habit.

Not a great shot of it but in the photo its growing just to the right of the barrel and in this shot is just beginning to send out new green growth. The tree is more easily appreciated when it doesn't have leaves--the branches & trunk grow in a corkscrew shape.

{{gwi:198907}}

I searched some more, first German, than English websites, looking for "perennials for clay soil".
one particularly nice pdf popped up, have a look, if you are interested,

bye, Lin

Here is a link that might be useful: best plants for clay soil

Ummm, there's some invasives in that .pdf list, so please be careful to do your research before planting any of those, as you will get more than you asked for! You may be able to already spot the invasives, so I will add this also for anyone else perusing this post for their own gardens.