Is HoA responsible for trimming a tree?

[Alex Dutton]

I own 4 of 6 units in a three building multifamily (two units per building). The HoA agreement has been lost to time and I'm not excited to renegotiate. There is an oak tree whose limbs are encroaching on the rook of one of the three buildings. It also has some dead limbs hanging over the parking lot. 

Since I own both units of the building who is under siege from the tree is this an HoA issue or something I need to deal with myself? Does the fact that tenants cars are also in jeopardy change the answer?

Thank you in advance for any feedback!