deemkelleher,

Please let people know your general location so they can hopefully help you better.... Thanks

Oh, silly me. I am in MA, zone 6. Thank you!

If the wall of flowers is viewed from a distance, then I'd go with Knock Outs --though I'd get the Double Pink Knock Outs instead of the cherry red ones.

If the wall is viewed more up close, then make a perennial bed in front of the forsythia and other stuff making up the wall. The salvia only blooms the first half of summer (purple) and the balloon flowers bloom the second half of the summer (blue). By themselves they won't make much of a show, however. Perhaps plant some yellow yarrow with the purple salvia and some white and pink garden phlox to go with the balloon flowers. That would make more of a show.

I guess you could mix the Knock Outs with the perennials also--though the KOs are going to get much, much larger than the perennials will.

Can't say about the nandina--never have grown it, but my general impression is that it might work there instead of the Knockouts or the perennials, so if that interests you, go for it.

In the meantime, here is some free advice: try to get those peonies settled in a permanent home (and don't plant them too deep or they won't bloom). They resent being transplanted.

Good luck--and give us some pictures when the "wall" blooms!

Kate

Nandina is one of my favorite plants for difficult spaces. It can thrive in low light and very dry soil and its evergreen. Roses need ample water to bloom well - if you can provide plenty of irrigation they will bloom all summer. If you can't water in that area, they will shut down in summer heat. Also, deer don't touch nandina while roses are one of their favorite snacks. So the choice just depends on location.

Thank you for the tips. The space is in full sun. I'm not worried about watering. As for the knockout roses, I was under the impression that they will stay smallish if you prune them.
In any case, I've uploaded a picture if the space, with the peonies still there. Also with a caution fence where my husband was trying to keep dogs and kids off newly planted grass.
And, yes, I know that the peonies are going to resent the move, but they will eventually enjoy their new home once it's been made.
Thanks again for the advice. More comments welcome...
Thank you.

If you can grow nandina, then the Knock Outs will be difficult to keep small.

Wow, you have so much space! MG is right on -- Knock Outs that are pruned to the ground in spring here (northern Virginia) are 6x6 in August. I'm counting the tree trunks in your photo thinking that there will be a lot of root competition and I still vote for nandina or nandina plus perennials. Is there another spot in your yard where you could make an island bed for roses?

Okay, nandina it is. I can put the roses on the other side of my property. Unfortunately, I put them in a perennial bed thinking they wouldn't get much bigger than three feet. Oh well. What perennials do you suggest with the firepower nandina? I'm thinking of geraniums, coreopsis, and heuchera. Maybe also putting in a climbing vine on one or both the corner trees.
Thanks so much!