the hedge has been trimmed to overhang the grass line by about a foot
This will be up to you! You can leave a little room to mulch, or you can lay the grass all of the way up to the shrub.
Here is more information on the grass:
https://www.gardeningknowhow.com/lawn-care/specific/st-augustine-grass/st-augustine-grass.htm
In March 2022, I had st Augustine sod put in my yard. It was very lush and green till June when temperatures were in 90s to over 100 degrees. I watered every other day 10 minutes in morning and 19 minutes in evening. The green color has faded to a tan color. Some spots are still green along the edges and around tree. What happened? Did I water too much. We have not had rain in over two months. What should I do?
Once established, they need little moisture, so it may have been overwatered. Cut back on watering to once a week, and when you do water, water deeply.
This info should help:
https://www.gardeningknowhow.com/lawn-care/specific/st-augustine-grass/st-augustine-grass.htm
https://www.gardeningknowhow.com/lawn-care/lgen/hot-weather-lawn-care.htm
https://agrilifeextension.tamu.edu/library/landscaping/maintaining-st-augustinegrass-lawns/
My soil is sandy, not very fertile, and I've pulled lots of crab grass out. I'd like to add white clover to my St. Augustine grass to help add nitrogen naturally and help crowd out crab grass next spring. Will that work in Florida? Or will the clover crowd out the St. Augustine grass?
The first article includes some information about white clover to consider before adding it to your lawn. It does say you can mix it with a high traffic grass to avoid the dead spots from walking on clover. Also note that clover may shade the St. Augustine, causing dieback. (you may want to use the microclover) It also may act as an annual in Florida, so you may need to let it mature enough to produce seed for reseeding, or add additional seed each year. I also included a link to find your local extension service, who can guide you on any merits or pitfalls in adding clover to your lawn in Florida.
https://www.gardeningknowhow.com/lawn-care/specific/st-augustine-grass/st-augustine-grass.ht
https://extension.umn.edu/landscape-design/planting-and-maintaining-bee-lawn