Des Higgins writes

ok, for common usage, referring to insects (or spiders) as "he" or
"she" is unusual but not unheard of. Usually it would be "it".
Referring to mammals as "he" or "she" would be quite common if you
knew the gender (especially for pets). Referring to plants by gender
would be rare and quaint and just for special effect; normally it
would be "it". Most people would not have heard of dioecy or would not
realise that male and female plants existed and would not refer to
such plants by gender.

People will often use 'he' or 'she' for an animal to express endearment,
eg when watching the antics of a particularly handsome spider. People
tend not to do the same for plants, since few people regard plants as
having a mind in the same way that an animal does.

--
Kay