You can keep your plants thriving during the hot summer months by inserting PVC pipes in the pot or hole when planting. Cut your PVC pipe about 12-15 inches and drill several holes in them. You can water and fertilize directly into the pipe ensuring that the water reach the roots.
Here is an example of the PVC pipe with holes drilled in it.This is a PVC pipe inside a pot of lavender and marigolds. The pipe is two inches above the soil but hardly noticeable as the plants cover it up.