Hoya rintzii is named after R.E. Rintz who studied Hoyas in Peninsular Malaysia. He had previously identified it as H. erythrostemma, which is native to Thailand. It is one of three Hoyas in the Mindorensis Complex in Borneo. Its leaves are much bigger than the other two: Hoya mindorensis and Hoya elmeri. Also, its flower ball is smaller than on the other two. This plant lives in the tree canopy in the lowlands along rivers seldom at elevations above 500 meters. These lowland species are known to like it really warm and make pretty poor houseplants unless you live in the tropics and don’t use your air conditioning.
I received Hoya rintzii as a rooted cutting from AH Hoyas of Thailand in May of 2017. It came in fairly nice shape, but was rooted in coco husk, which often posed problems for me. I put it into a 2 inch net pot and hoped for the best. I knew nothing about this Hoya going in and that was probably a mistake. I found out later that it is in the Mindorensis Hoya complex, and H. mindorensis has always given me nothing but trouble, because I simply cannot give it warm enough temperatures. It was not long after potting up Hoya rintzii that I needed to take cuttings and start it over because of root rot.
The second time was the charm with this one, the cutting I took of Hoya rintzii took off and grew this time because I was able to keep it warmer and watered less. I found out that the leaves are highly variable in size as you can see in the photos below. I was thrilled in April of 2019 to see the first signs of a peduncle, which held on and budded up in short order. The buds opened one morning and were very similar to Hoya erythrostemma to my eyes and were quite beautiful.
I will end my discussion of Hoya rintzii. It is a Hoya best left to those with very warm outside conditions in Florida or the tropics. It could also be grown by those that have very warm, humid grow tents in the house. For those of us in the cold north, it is a Hoya best steered away from unless you want to torture yourself.