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.  
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IMG_1366Here is an example of the PVC pipe with holes drilled in it.IMG_0059This 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.