Elaine is spot-on. Alkalinity is not good for most plants. Some love it, but few and far between. Alkalinity makes nutrients into a chemical form that is unavailable to most plants. Florida sun from 11-7pm is brutal.
Maybe you could fix the soil pH, and continue to add organic stuff like mentioned above, and plant your full-sun, xeriscape plants in the WINTER and allow them to slowly adjust to the sun, and then by summer they will have acclimated naturally?
I have two HUGE expensive Uncarina trees that I planted in that fashion....they were always grown in a greenhouse though they naturally originate from a hot, HOT place. I had them sent over in the winter, while they were dormant and had no leaves. Left them in pots while they were sleeping, planted them in the spring when they woke up. Then, by summer, they were ready to rock and roll and weren't at risk of being cooked after 14 years of living in a shade house/green house.
