Hi Mike,

Yes, core aeration can damage tree roots if the tines hit them--large surface roots can generally be avoided but if enough surface roots are present it will render aeration basically impossible without causing some damage to the trees.  Depending on your landscape goals, you might take a couple of different strategies.

To improve the health of the tree or trees, consider that the roots extend will beyond the drip line (and probably well beyond where you can see surface roots)--good core aeration here will help the soil conditions for both the tree and the lawn or other plants.  Make sure the cores are on 3-4" centers--it will take at least two passes with the aeration machine.

Nearer the tree trunk, two (expensive) options are available for the tree.  One is to use "coreless" aeration with a high-pressure water injection.  This technique is used on golf courses; a large enough lawn care company may be able to offer this service.  A second option is to have a tree company use high pressure air (and air spade) to excavate around the tree and to add uncompacted soil back around it.  The air spade would be completely destructive to a lawn, though.

You might consider removing any lawn around the tree and replacing it with wood chip mulch.  This does not solve compaction issues in the short or even medium term, but it makes the surface roots less visually affronting and prevents them being damaged by a lawn mower, for example.  

"Liquid aeration," as marketed by many companies, is in essence wishful thinking.  The ingredients of many are proprietary, but at least some contain wetting agents and surfactants, which might help water to infiltrate the soil surface but which do nothing to space the soil or improve soil bulk density.  

I hope this is helpful!

Cordially,

John



Hi Mike,

While a watering schedule can't substitute for aeration, using a cycle-and-soak schedule, where water is applied a bit at a time and allowed to soak in between running can help water infiltrate poorly drained soils.  For example, if a zone were to run for 12 minutes, you could split it into 4 runs of 3 minutes each, separated by enough time to prevent run-off of the water into the gutter (how long this will be depends on your soil, start with 10-15 minutes and work up from there as needed).

You could also use nozzles known as stream-rotors.  These have a lower water-application rate than "classic" pop-up spray heads so they need to run longer to apply the same amount of water, but more time is allowed for the water to infiltrate the soil.  The nozzles can be easily switched from the more standard pop-up spray heads to stream rotor heads.

You might find this section of the Colorado Master Gardener training curriculum useful:

https://cmg.extension.colostate.edu/Gardennotes/265.pdf

I hope this helps!

Cordially,

John