It depends on what your water pressure is, but this is what I thought of first:
This looks be the improved, more user-friendly version of the micro spray stakes that I purchased a bunch of years ago. By using the 360 degree nozzle,
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placing it a little distance away from the trunk and angling the stake so the water directed at the tree trunk has a higher inclination, you will be able to cover nearly a complete circle. In order to get the maximum pressure and flow you will want to stick with your large diameter supply mains and run a 1/4 line that is not overly long. Orbit makes a plug product to fill the extra holes in your mains so you don’t have to purchase new tubing.
Alternatively, you could place two of the 180 degree nozzles on opposite sides of the tree trunk.
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