triggers are not shared between parent and child tables?

I implemented table partition recently and found that the tiggers on
parent table are not working any more, except the before insert trigger
which redirects data to children table. The after insert/update triggers
are not working now. I understand the after insert trigger may not
working since the before insert trigger redirects inserts to children
table and returns null. But why the update triggers are also not
working? I googled and found this
article(http://www.peachpit.com/articles/article.aspx?p=31206&seqNum=3)
mentions "triggers are not shared between parent and child tables". is
it true? Maybe I overlooked but somehow I didn't find this in partition
part of postgresql
doc(http://www.postgresql.org/docs/9.1/static/ddl-partitioning.html).