Interesting Watering Systems for New Plantings

Touring  Baynard Ruins in Sea Pines Plantation on Hilton Head, we saw these interesting methods for watering newly planted tropical plants.

Closer view shows the bag acts like a rain barrel.

The smaller bushes have a similar system but it takes a hose also.

Or is it just weed control?

Surely it drips water also...

I need to do some research on these methods.