A newly planted hedge, or any other plant, will often need a lot more water than one that was planted a few years back. This is because the roots are trying to settle down and establish, and are not yet deep enough to be able to source water and nutrients themselves- therefore being reliant on you to provide them with enough water until they're able to look after themselves (pretty much!).
With that being said, the trick to watering your plants is by watering thoroughly a few times per week, instead of a little every day. The best time to do so is first thing in the morning or late in the evening, when the sun is not blazing. This will ensure the water has a chance to get to the roots before it's evaporated by the sun- please ensure you water directly on the roots and not on the leaves (water on leaves can lead to scorching).
Please also note that not all plants require the same amount of water as others and prefer different soil types. For instance, Lavender prefers a dry soil, whereas Dogwood prefers a wet soil. In this case, the best way to identify how much water your plant likes is by looking at how effectively it soaks up the water. If water sits on the top without soaking through fully, you will need to water less or in smaller quantities; whereas, if the water is soaking through quickly, and dries up quickly, your plant will likely need a little more water. This is the best way to ensure your plants do not become waterlogged.