My mallows do best in partial sun .... given your zone I think it would be the same. Full on zone 8 sun all day is hard on mallows, but they will survive with frequent watering. Can you give them some relief from the intense afternoon/evening sun?

I have a Moy Grande which is a cherished plant .. I grow in a pot and give it some afternoon shade. It is spectacular.

Thanks so much for the reply Robyn. I have another flowerbed by my front porch that gets morning and midday sun but shade the rest of the afternoon. Its been difficult keeping the plants in the flowerbed in full sun watered the past two years. I even put down mulch but it still didn't help. I may grow some in containers. Thanks again for telling me about partial sun, I would hate to see my hibiscus plants cook in the sun lol. I'm getting some dinner plate hibiscus seeds next week.