Aerate Soil Around Trees by Coring not Punching Holes

Q. You mentioned drainage could be a problem for my trees.  When I water with the drip process the water does pool but eventually drains. I have not dug up the ground to see if the roots are wet and lying in water, but I did take a 2 foot spike (1/2 inch diameter) and drove it into the ground around the tree. Seemed like a good way to help drainage. Is it?
A. For now, yes, you could punch some holes in the soil down to a depth of 18 inches but taking soil cores out (e.g., post hole digger) is much more effective than punching holes into the ground with a solid piece of metal that compacts the soil on the inside of the hole.

The best way to get some drainage over the long haul is to cover the soil with organic mulch rather than rock mulches. As the organic mulch dissolves or breaks down and improves the soil then water will drain better. Increase the time between irrigations when you use mulches of any kind. Mulches will keep the soil wet, longer.