I am a zinnia enthusiast/hobbyist, so I would suggest you include some zinnias. For ease of maintenance, I would suggest Zaharas and/or Profusions.

Being on the south side you want something that can tolerate heat. I have flower beds in full sun like yours so I'll try to tell you what I have success with.

You can't go wrong with Magellan Zinnias or any zinnias really but I just love the Magellan series. They have huge 4 inch flowers on a 12 inch plant.

Marigolds would do well there. They can take the heat and keep on blooming. Janie is only 8 inches high and has a profusion of blooms. I like Janie Yellow but there are many dwarf varieties in varying colors.

Zonal Geraniums may be a bit taller but can take the heat and don't mind drying out.

Portulaca(often called moss rose for it's rose like flowers) is a low growing annual that loves the heat. As a bonus it will drop seeds and come back another year or you can collect seeds from it. It comes in many colors and makes a terrific edging. I wouldn't plant petunias there

Thank you! Great ideas! I had Magellan Zinnias bookmarked...love them. My next door neighbor had the best luck with the zonal geraniums last year.

What might be a good combo for the zonal geraniums?

dusty miller! What a great idea-- I remember using that in my bridal bouquet. It'll look so pretty with the red geraniums I think!

How about calendula? I only grow them in containers, but I love how I can just jam pack them in and they give me tons of blooms.

My design savy sister in law always planted the deep red (not orange) geraniums in the dirt, along with "compact" dark blue Lobelia and finally white allysum. They were just dotted here and there, no straight formal planting. She always purchased medium sized plants, so they put on a striking red white and blue show all summer long. That combination was so stunning, for color and for the texture the three plants brought to the landscape.

I'm the OP and I wa yes to update! I did a mix of a ton of things and what did best for me was white lobelia, purple fountain grass, purple sweet potato vine and dusty Miller! As expected, petunias are so-so and diamond frost was ripped out right away. I also planted some new boxwoods and three verigated dwarf rose of Sharon.

I grow these "annuals" in HOT exposures:

marigolds, grape vinca, celosia, COSMOS, Sunflowers,African daisy, Gerbera Daisy, portulaca (which often reseeds), and dusty miller (perennial here), but why not mix in some hardy perennials that are also colorful, heat/drought tolerant and come up every year on their own. Of these, I especially like Coreopsis, Black-Eyed Susans, Russian Sage, and Purple coneflowers.

thx for the update .... good job ... ken