Determine if there's a feasible way of draining excess water someplace else. Of course, you can't drain to someone else's property.

If not.....find another place for the Leylandii. They will not tolerate wet soil.

what is the base soil .. and how long did the water stand ...

in my sand.. if i had a puddle like that.. immediately after rain ... within MINUTEs.. it would be gone ... lets say 15 mins.... and that would be near irrelevant to the trees ... in summer ...

winter would be a whole different thing ....

not enough facts to answer.. IMHO

ken

Can take a few days to drain, but can also rain a few day's! There is no way to drain the water and I planted them all myself, I'm in my 50's and have bad arms, so I learned a pricey lesson.
Thank you for your advice

As a WW2 veteran my Dad was fond of saying 'Time spent in reconnaissance is seldom wasted.' I think you've discovered the hard way how true that is ;-) It is always a good idea in gardening to wait and observe before taking action on pretty much anything, except perhaps a cat about to perform in your seed bed.

you dug all the holes..

what is the soil type ...

ken