The development that I live in has recently planted bushes (leaves on them-not shrubs) and they have been challenged with the plants not surviving. I noticed that a company came in to water them in the full hot sun. Even the new plants that were put in to replace the ones that did not survive are now looking the same way. I was always under the understanding that you do not water in the full sun except at the base of the plant.
Does Watering Plants/Bushes Burn Their Leaves Hence Killing the Plant?
Certified GKH Gardening Expert
Technically, watering under full sun will not harm a plant. It is actually a myth that water on the leaves will focus the sunlight and burn the leaves. It is not scientifically possible.
That being said, if it is very warm where you are, watering at full afternoon will significantly reduce the amount of water that will get to the roots as the water will evaporate quickly before getting to the roots, thus the plant dies due to a lack of water. This is normally not an issue as most people watering during the hot afternoon will water enough to compensate for the water lost to evaporation so it becomes a matter of conservation rather than plant survival.
In your case though, being in a development, I am willing to bet that you have pretty thick layers of mulch laid down, which adds another barrier to the water getting to the roots (dry mulch actually repels water. If this is the case, even watering in the evening or morning may not solve the problem if all they are doing is a quick run by with a hose as the water will just sit on the top layer of mulch before evaporating when the heat of the day arrives.
An irrigation system (which can be surprisingly affordable) set with timers that will water long, low and a few times a week would be better than overhead watering done quickly and daily. At the very least, you may want to see if the landscaping company can take more time with the watering to ensure the water makes it through the mulch and deeper into the soil where it will not evaporate.