Anon, I believe that the original statement established at the HOA "instructed" the landscaper to cut the trees. Therefore, while you section on "reserves" is one hundred percent correct, it does not however apply here. Once the HOA "instructed" the contractor to take action, the responsibility resides with the HOA.
To the original poster, just because you attended a meeting, does not suggest that effort (on both sides you and the HOA) was properly administered towards a solution. Yes, you do have the "right" to sue your HOA, but you are (again) effectively suing yourself - and the fees, court costs, etc, are funds that I am sure you might agree could/would be better spent as part of the HOA's budget, not with those that will collect them (process server, attorneys, courts, etc).