In Hawaii, a legal fence is considered to be one that is “not less than four feet in height and made of stone; posts and rails; posts and boards; posts and wire; or other suitable materials.” Since land surveys were less accurate a few decades ago, Hawaii’s older neighborhoods have seen some issues with encroachment. In response to these issues, Hawaii created the “de minimis law”.
The de minimis law states that (via FindLaw.com):

Hawaii courts hold that a landowner may always, at their own expense, "cut away only to his property line above or below the surface of the ground any part of the adjoining owner's trees or other plant life." Proceed with caution though, as you may be held liable for damages if you kill a tree or plant.
Life in Hawaii affords many great pleasures, one of these being the incredible fruit trees that grow abundantly here. If a part of a fruit tree is on your property, in Hawaii, that part is considered to be yours, and therefore so is any fruit that it bears.
Even if you are someone who is not bothered by encroachment, it’s best to know your rights, in case you have a neighbor who is. For more information on this, click here.