I have a lot of trouble rooting bella in water. I would try rooting them in pure perlite with a plastic tent. There's something about perlite that seems to encourage rooting, but you do need to pull the tent and mist the perlite every day or two because the water evaporates quickly. Maybe someone with good success rooting bella will have a better suggestion. I always think going into winter is a tough time to root anything, but that may not be an issue in sunny Florida.

Denise in Omaha

I rooted one (6 nodes) experimental cutting of Hoya bella in a baggie. I put the cutting in a baggie, sprayed some water/superthrive inside, blew the air and closed with a plastic clip (can use also zip lock bags). I did blow fresh air every two, three days and sprayed when lack of humidity showed. It took although couple of weeks (sth like 5-6, I think), roots appeared at the very end and I potted up when they were 0.75-1 cm. Cutting is still alive in a pot :) If you could add some bottom heat to this I think it would root faster. My mother-in-law managed to root some Hoyas in 4-5 days in here seedlings dome over a heat mat. I don't know the exact elements of her system so cannot advice here. I kept mine in light place, away from direct sun.
I must say that I would never believe in 100% rooting statistics in this periode of year but recently (during October and November) I rooted like 27 different Hoyas (some with multiple cuttings) with this baggie method. I did not succeed with two additional which I took of the baggie too early (no visible roots produced), the patience is important for some resistant ones.
I heard, as well, that some people root in perilite with bottom heat with great success.
Everyone has his preferred method (water, perilite, baggie, soil...) so maybe try more than one with your cuttings and see what works best for you.

With a baggie method, Bella produced the roots at the end but most of Hoyas produce roots along the stem and sometimes the fastest are those at the top.
Here is a photo of a small nummularioides cutting in a baggie. And his roots today...

http://i7.photobucket.com/albums/y275/ema_d/Baggie3.jpg

http://i7.photobucket.com/albums/y275/ema_d/Baggie4.jpg

HTH,
ema

Ema - I read about and then tried this method this summer and I didn't really have much success. I'll be trying it again as spring approaches just because it kind of fascinates me, but you're right - seems like we all have to experiment until we find what works well for us. I also think that what works with one species may not work so well with another. I root carnosa and pubicalyx in water all the time with great success, but bella and a few smaller varieties resist rooting in water for me. Trial & error is how you learn!

Denise in Omaha

I am new to rooting hoyas so, when I received some lovely long cuttings of five or so varieties this fall, including Bella, I cut the cuttings into smaller pieces and placed half in water and half in free-draining, perlite amended potting soil with baggies over them. Hands down the baggie method worked best for me with all varieties, so much so that I transferred all surviving water cuttings to pots and baggies.

I find the easiest method is to layer off a shoot from the parent hoya in a small pot alongside the motherplant.
I have done this many times with H. Fungi and H. Carnosa, with a 100% success rate.

If a loose cutting is obtained, a heatmat is advanteous.
The extra temperature seems to help in the rooting process as well as applying some rooting hormone on the cutting.

Ensure that the new cutting doesn't dry out.
I use very sandy potting mix.

Good luck!
Raymond