Many hoya collectors have debated the issue of whether to stop attempting to root during certain months of the year and the consensus seems to be that it is a ‘No No’ from October through March. I suppose if you reside in the southern hemisphere the months will be opposite but I am being specific to the northern hemisphere. For many years I had slowed down on the rooting of cuttings during those months too but only because the area I was placing the cuttings was outside where the daylight had changed with the sun’s angle and the daylight hours had diminished greatly. Another factor was the chilly nighttime temperatures. If this is the case, I would agree that rooting is an expensive and frustrating waste of time.
The way I have continued to root with almost a 100% success rate is using bottom heat and grow lights for assistance. The bottom heat is provided with Heat Mats that are about 78°F and constant and T5 fluorescent lights that are shining down for 14 hours per day. Roots are evident after a week or so and when I reduce the amount of water given to the mix the cuttings fill out the tiny pots with a strong root system. After about 2 weeks I notice new growth on the majority of the now ‘Plants’. At that point I treat them as I do my larger plants but do not repot into a larger pot. Many of them are even pushing out flowers on the existing peduncles.