I have some Campanula glomeratas that fit the height you want. I don't know if they'd like part shade (mine are full sun), but you mentioned black-eyed Susan and coneflowers, which are sun plants, so maybe your spot gets enough sun.

These campanulas bloom fairly long for a perennial. They do reseed and some consider them invasive, but mine aren't that bad. They're certainly not the thugs that nepeta or oenothera have become in my flowerbeds!

You might also try some salvias. I have Salvia East Friesland, which stays about one foot tall. I hear that the 'May Night' variety has a longer bloom season and would be worth looking at.

Let's see, those are both purple. For some yellows, there are a number of Coreopsis varieties that may work. There are the broader-leafed grandiflora types and the threadleafed verticillata varieties (I like both the common 'Moonbeam' variety and a warmer yellow 'Zagreb'). I think Zagreb can take a little more moisture than Moonbeam, too. Zagreb stands a little taller than Moonbeam, too (but not higher than your limit).

I also am really enjoying a perennial Lavatera with pink hibiscus-like blooms. It's Lavatera tauricensis, which I haven't seen in nurseries, but I got seed from Thompson and Morgan a few years back. It was supposed to be a zone 7 plant, but it's done perfectly well in my zone 6 yard, even when we got to -7 degrees this January. It bloomed nonstop last summer. I have some photos at the link below.

Here is a link that might be useful: Lavatera on my website

Well, I call the garden "part sun" because it gets sunrise to approximately late morning rays & late afternoon or evening to sunset rays.

That lavatera is pretty! I do like coreopsis too.

I'll look into those. Thanks for the recs!

I went to Valley Nursery in Uintah & got a Coreopsis, though I already forgot which one. It's a light yellow, almost ivory. I figured my little perennial garden didn't have enough white tones. ;-)

Hey Stevation - you're Lavatera tauricensis looks a lot like my 1 gallon 'Desert Hibiscus' that I just bought from Star Nursery! I don't know if they are the same, I'm not sure on the proper name for my plant, it wasn't on the tag, and googling 'Desert Hibiscus' doesn't find me a picture of my plant. It looks like the petals on yours are disconnected, mine are connected, like a little cup. :) I'll try and post a pic of mine and see if you think they're the same.

Hi Tweedbunny,

I hadn't seen desert hibiscus before, but I just googled it and found this link. Is that it? There's also another hibiscus that goes by that name, but it's a yellow flower.

Anyway, That does not look like the same plant. It looks woody. My lavateras are much more herbaceous, with greener stems. Lavatera is in the mallow family which is related to hibiscus, I think. They certainly have the same general flower structure, but it's not an actual hibiscus.

I have four or five seedlings of this lavatera that I grew in my basement this winter, and I'm excited to find some spots for them out in the yard. I don't think they'll flower the first year, though. Gardening does teach patience. :-)