Hoya danumensis is named after the Danum Valley in Sabah, Borneo. This Hoya was in the trade for a very long time where it was mistakenly being sold as Hoya wallichii. The plant was correctly published as Hoya danumensis in 2009 by M. Rodda and T. Nyhuus. “Hoya danumensis is found in lowland to hill mixed dipterocarp forest and also in hill forest on ultramafic soils at 100-600 m.” From the book A Guide To Hoyas of Borneo by: Anthony Lamb and Michele Rodda.
I first tried to get this plant from Thailand, and because it is one of those thin leaved species that don’t travel well, it was dead on arrival. I was quite surprised when I received a cutting of it in a trade with a collector in North Carolina in the Summer of 2018. Hoya danumensis is supposed to be difficult to root, but I did not have any trouble; first rooting it in water and moving it over to soil. The plant did okay at first putting out a strong vine, but the new leaves were sparse and began to show chlorosis. Within a few months it had ceased to grow, and when I took it out of its pot, the roots were heavily rotted.
After discovering rot, I took a cutting and restarted the plant. I used a net pot this time so that I could more closely monitor when the plant was dry enough to require watering. It grew strongly at first putting out a long vine sparsely populated once again with chlorotic leaves. Despite the mangy chlorotic leaves, the plant managed to put on three different peduncles on these long mostly leafless vines. It was nothing however to get too excited about as it began blasting buds just as they would begin to form. I tried everything from different fertilizers to different locations all to no avail; the buds continued to blast.
After bringing my plant inside the house, from being in my summer greenhouse, inexplicably on one of the peduncles, the buds actually began to grow. I had it under LED lighting in my basement grow-tent in a four inch net pot inside of a cache pot. I was amazed at the size of the buds as they kept growing. They were roughly twice the size of the buds on my previous campanulate Hoya species H. campanulata. Finally after 2 years of fooling around with this plant, one morning the first flowers began to open up, and I was blown away by how large and beautiful they were.
I have wracked my brain trying to figure out what causes this condition in some of my thin-leafed Hoya species such as Hoya phyllura. I’ve tried different fertilizers, growing medias, growing it drier, and warmer but I can’t seem to solve the puzzle. I don’t know if it could be a pH issue with the nutrients getting locked up because of the media being to alkaline or acid. All I know for sure is that it is frustrating as I hate yellowing leaves! The flowers on Hoya danumensis are absolutely outstanding and probably the nicest on any of the campanulate Hoya species. If I could only figure out why I have yellowing leaves, I would give this plant my highest recommendation. It is worth picking up though if you can find it as your growing experience might be totally different from my own.