Auk, I always think "she" (but I don't write it in English ).
In French, tree is masculine; in Portuguese (my mother tongue), and other languages, tree is feminine (these languages don't have neutrals.) So, some people like me say tree and think "she".
In Dutch they are neutral, whether they are actually female or male. To me it sounds silly to use he or she.
Even sillier I find it to give them pet names like Bonbon, Milo, Dolores...
It comes down to the grammar , even inanimate objects are named with female or male properties for example : the pen in Italian is " la Penna " la is used for female things like the woman " la donna" but for male things for example: the fridge " Il frigo " il is used as " the" for maschuline things , the male " Il maschio" .
Sorry for the very bad explanation but I hope you got the gist of it
It comes down to the grammar , even inanimate objects are named with female or male properties for example : the pen in Italian is " la Penna " la is used for female things like the woman " la donna"