Hoya ruthiae was named after Dr. Ruth Kiew, a tropical botanist based at the Forest Institute of Malaysia. It was described in 2015 by Michele Rodda. The plant has clear sap and grows on limestone formations. The flowers when first opened are about 1/2 inch across and are relatively short lived, lasting about three days.
I received Hoya ruthiae as a cutting from Thailand, way back when it was still called Hoya sp. UT-168, in the summer of 2013. I got it to root, but it showed very little growth. It might have put on three leaves with almost no vine over the course of the next year or two. I finally pulled it out of the pot and saw unmistakable signs of root rot. I managed to get just enough of the plant to take a couple of small cuttings and start the plant over again in 2015. Once again it rooted and only put out a couple of leaves and then lost one of those. I checked the roots in about a year and sure enough more signs of rot. By then it was late in 2016, and I barely had enough plant to take a single cutting that I was sure would fail.
When I started Hoya ruthiae over again at the end of 2016, I had discovered net pots which gave me far greater knowledge of when a new plant actually needed to be watered. I started my meager little cutting in a two inch net pot and not only did it start to root, but started growing stronger right from the get go. I don’t know if it was the breathe-ability of the pot, or what by I was pleased at the rate of growth. 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.
After adding ground oyster shell to the mix the plant continued to grow pretty well. I compare the plant to Hoya padangensis both in appearance and growth habbit. The leaves come in an attractive dark green with speckles and then fades to a flat yellow green. The plant is far from attractive as can be seen in the photo below. When the plant was about 15 inches high, I moved it under its own LED light and shortly after it surprised me with a peduncle that actually began to bud up and on more than one peduncle.
Only having seen the flowers of Hoya ruthiae in photos on the internet, and in a book, I somehow expected them to be larger than they actually are. The entire umbel of flowers are only around 2 inches across. Whatever they lack for in size though is more than made up for how photogenic they are. They take a heck of an impressive photograph! This plant is definitely not a Hoya for beginners, but if you want a challenge, have the prerequisite place to grow it, with very high humidity, warmth, and follow my instructions on the use of net pots and adding oyster shell to the mix, it might be for you. It took me five long years of patience and dedication to flower this plant, but knowing what I do now, it could probably be done in about two years of high intensity growing.