1) You need a plant import licence issued by AFCD ( just fill in the form in the website and received by email is OK, very simple and easy ) and
2) a Phytosanitory certificate issued by Taiwan Agency ( you may get one at the Plant inspection airport counter. They may have office hour and you have to check )
3) Presernt both certificates at Hong Kong airport Custom counter with the plants and you might required to clear the plants at the AFCD office )
From China:
May not need any special certificate for those that are not controlled under CITES
Better call AFCD for official and updated information. ( Specify importation of plants from China that are NOT on CITES list )