I'm in the process of transplanting daylilies into large containers. They would do well in your situation but they have a grassy like folage
that comes up in early spring and flowers in June.
If kept watered they will stay green all summer and some bloom again in early fall. They come in a varity of sizes and colors. I asked the same question on container gardening forum and perennial forum. you might also try there.

Welcome Newbie24!
Questions - How big will your planters be? How tall would you want the plants to be?
If you want shrubs, there are some dwarf varieties of nandina that would tolerate afternoon sun and would have colorful foliage all year. Lowe's should have at least a couple kinds. They stay fairly small so maybe you could plant some of those or other small shrubs along the back and still have room for a few flowers in front of them that would hang down over the front of your planters. Be careful not to get shrubs that will get too big. I'll warn you, the description on the tag often fudges on the size and they actually get bigger than what it says. I have a 10 foot "dwarf" burning bush that was only supposed to get 5 feet tall and I've pruned it back a few times. That seems to be common with many dwarf shrubs.

Remember that plants in containers will have a more difficult time over-wintering as the roots can freeze much easier. That is what makes me question whether or not shrubs would be a good idea. The larger the pot, the less likely your roots will freeze. Also unglazed terracotta will surely shatter if wet and frozen. Hope this advice is not too late. Good luck.

The advice i got on helping prevent freezing in pots was to pile leaves (which i have plenty) all around the pots and over the pots some too.
vickie

Check with your state's Extension Service. Each county should have it's own Cooperative Extension Office which provides free publications and information for the asking. They will have valuable vegetable/gardening tables available specifically for your area determined by universities and horticultural research scientists who have collected data from growing those plants in your state. Your tax dollars are already paying for this service so you may as well get some use out of it.

They've got guides they'll send to you for free for the asking. Tell them what you wrote in your first post and they'll set you up and put it in the mail today.

We have barberry bushes, english boxwood, daylilies, purple coneflowers, lavender, black eyed susans, salvia, spirea, and yuccas (in spite of the fact that we dug them up like 6 times...they don't die easily). The barberries were supposed to be 3 feet tall. Yeah. They are as long as you prune them regularly.

Trisha