How careful do have to be when turning soil around recently planted trees?

Question

have a hedge row of conifer trees (Tsuga Canadensis/ Canadian Hemlocks) and would like to turn over the ground with compost around them in order for them to be able to grow roots easier into the clay which is currently surrounding them.

why and how so?

btw, is middle summer okay to do this or would it be better to wait until fall?

why and how so?

thanks for your answers!

Answer 1

If they are a year old then it wont matter; just dont dig too deep when you turn the soil.

Answer 2

I would not do anything for at least a few months. The roots have already be traumatized by the planting.  Mulch around it and in the fall turn the dirt.