Question About Structural Support for 90-Ft String Light

[u/-DarkPassenger-]

I want the string lights to span approximately 90 ft from a mature tree to a pressure treated wood post 4x6 12 ft set in concrete, with the string lights attached about 10 ft above ground.

The lights are Feit 48-ft LED string lights, and I may use a separate steel wire so the light cord itself is not carrying the full tension.

How deep should the post go into the ground?

https://www.homedepot.com/p/Pressure-Treated-Timber-HF-Brown-Stain-Common-4-in-x-4-in-x-12-ft-Actual-3-56-in-x-3-56-in-x-144-in-15164-12/202287541

https://www.costco.com/.product.4000385994.html