Yes, trimming the tops will thicken up the hedge. For future reference, to get a really thick hedge right to the base it is best to plant smaller plants in a staggered row and cut them as they grow.

there is NOTHING you can do with a 3 month old hedge .. period ...

give it a full year.. and i bet you will be pleased ...

you would be better off.. watering properly.. rather than relying on a lawn sprinkler.. see link for info on such ... there is no way to find out except by inserting your finger.. or using a small hand shovel.. or even a tablespoon ...

imo ... every leaf is a food making machine.. i NEVER cut off anything.. the first year.. as it needs all its energy.. to form a root mass to grow the screen you want ...

be patient ...

ken

https://sites.google.com/site/tnarboretum/Home/planting-a-tree-or-shrub

I would agree if this were an individual shrub but it is a hedge and as such it needs pruning from early on to get a thick base rather than instant height. "New hedges require formative pruning for their first couple of years after planting." RHS

For optimum response mulch the soil around them. This is particularly important in a hot and dry climate.

Thanks, everyone.