It did not take too long to move from a two inch net pot up to a three inch.  It grew fairly strongly until the roots were coming out of the pot.  At about this time I received a book called A Guide To Hoyas Of Borneo where there was an entry on Hoya ruthiae.  It said that the plant was endemic to “Borneo and lived on the limestone of Bukit Baturong.” The part about the limestone got me thinking; so in early 2018 when I transplanted the Hoya to a four inch net pot I incorporated considerable ground oyster shell to the mix.