"There is much advice on the internet about how to care for Hoya curtisii from never let it dry out to keep it dry all the time. I can only say what has worked for me. The plant needs a relatively small pot where it can literally live for years (Mine has been in the same 4 inch pot for 4 years!). The soil should be relatively free draining, but also have some water holding capacity. Peat-based potting soil amended with 25% perlite should work fine.
This plant needs to be only watered once it has dried out. I’m a person who likes to water all of my plants on the same day each week, but with Hoya curtisii it won’t work. Water only when dry, then soak the plant, and start the process all over again.
Hoya curtisii will grow well in full sun or relatively little sun. It is pretty adaptive. I flowered this plant the first time after having it exposed to full sun out of doors for a full summer. The second and third time it flowered just as the days were beginning to lengthen in late February/Early March indoors in a northwest window with almost no sun.
There is no doubt that Hoya curtisii grows best in high humidity, but it will muddle along with relative humidity as low as 40%, but expect a lot of dried out growing tips. My plant lives year around now in my house witch gets pretty dry in the winter time. I think think this Hoya would like to live in a bathroom where it would get extra humidity from people taking showers."