Look at some tall columnar ornamental grasses, like Calamagrostis x acutiflora's various cultivars' 'Karl Foerster,' 'Avalanche' and 'Overdam.'

Also Panicum virgatum 'Heavy Metal' and 'Northwind,'

Plant them near the front of the bed, so there's at least two feet between them and the house.

Alternatively, there are lots of beautiful low and medium height grasses which would fit the bed well.

It sounds, from your description, like a hodgepodge of disparate plants. You want to get some continuity going, and a good way to do that is to repeat, spaced out, the same plant. Grasses are good candidates for this, because their habits work well to divide sections of the bed.

I'll admit that you lost me for awhile there. lol!

Sounds like you want a trellis and he doesn't. Does he just not want to attach a trellis to the house? if so, look into a nice freestanding one (stake legs go into the ground).

Without any trellis, you're talking about an area with the moonbeam coreopsis placed left of center? I'd rearrange/change some plants and position the tallest there, and have the height drop to transition to the next area with mostly shrubs. It's difficult to picture what you describe. It doesn't sound like a linear planting, if you were able to fit all of that into a 20-foot span. My mind is blank for any good tall perennials -- I tend to avoid them because I don't have much space. Your lupins will only be tall while blooming... same with things like oriental lilies. I keep thinking of annuals, but wrong forum. :)

Well being the daylily fan that I am, I am going to suggest a taller variety of daylily. It sounds like you already have some pink ones, so one that I like is frilly bliss, and it has a bit of yellow so should look good with your coreopsis, and lupine (not sure what color they are, but anything looks good next to a daylily) Here she is
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Her name is frilly bliss, I bought her from Marietta gardens online. Pretty tall should fill your spot nicely, I think. Just a suggestion, hope you like the pic, got it from tinkers daylily database. Good luck!

Thank you for all the suggestions!

"like a hodgepodge of disparate plants. You want to get some continuity going, and a good way to do that is to repeat, spaced out, the same plant. Grasses are good candidates for this, because their habits work well to divide sections of the bed." You got it! LOL It's where I started and it's BAD!

Love the grass suggestion, that's actually what we were talking about tonight at dinner.

"Sounds like you want a trellis and he doesn't."

Uh-huh! And it's not the TRELLIS he doesn't like, it's the stuff ON the trellis that he wants to avoid. He's spent 4 years on replacing trellises and hacking at a wild Jackmani Clematis and trying unsuccessfully to avoid a blood-thirsty New Dawn Rose. No climbers. It does need to be transitioned/re-arranged/whatever, I just have too much sympathy for my first babies to do it! They survived me!

Thanks again, all!

Be carefull which grass you choose! I planted japanese blood grass in my garden last year, and it has taken over!!! I just went crazy, I don't know what happened. There is blood grass blades poking up through my coreopsis, my my mini roses, my daylilies, everything! It is pretty but red grass does not look that nice sticking up through a pink rose bush!LOL I also have pink pampas grass that got huge in 1 years time, so be careful what you choose!

oh! given the trellis story, let me recommend a honeysuckle vine then: I have 'Pink Lemonade' (Lonicera heckrotti) and it's WONDERFUL. You won't have to worry about it reseeding or spreading out of bounds. The flowers are beautiful! Hummingbirds love it. And if you don't like the extent of it, you can sheer it back in spring as far as you like and start the vines all over again -- I'm sure you could even clip it back anytime, but since you're also z5 I don't think that need will ever come up. :)