Last summer, I ran into the problem with some of my potted plants which seemed to dry out way to fast under full sun, especially the ones that have well established plants. It seems like the soil looses it's capacity to hold any water when the roots take over the pot so one of my solutions to lessen the problem is mixing in water absorption crystals to the soil.
These crystals can carry 400 times their own weight in water, and they are supposed to last for multiple seasons, and they are supposed to be soaked in water before they are put into the pots to work best.
Here's the bags that they come in. I puchased 5lbs of this stuff so it should have the capacity to hold 2000lbs of water which should last me a while.
I added 3 handfuls to a bucket, and I'm trying out 2 4(gallon buckets). 3 handfuls looks like enough to suck up all the water in the buckets, and I was a bit surprised that there wasn't a drop of water left.
Here's exactly how it looks when I add this stuff and mix it in with the soil in a large pot. My only concern is for the crystals that are on the surface since they are the most exposed to the sun which may wear them out sooner, but I tried to mix it in as good as I can.
I've figured that I can add this stuff to any kind of plants whether it is a tree, shrubs, perennials, or even vegetables when I start growing them.
After mixing them into the soil, some of the crystals are still on the surface of the soil which shouldn't be a problem. I hope it promotes the roots to grow all the way to the surface which sometimes since the top layers are prone to drying very fast.