It could be that your Hoya is currently growing in something along the lines of Al's Gritty Mix and if you want to learn more about how to make that, there are a zillion threads about it (here and all over GardenWeb) if you do a search. Here is one recent conversation we had here about the use of sand in Hoya mixes.

On the other hand, if you are already growing successfully in the 'chunky mix' it might not be such a bad idea to switch your KQ to the same mix as the others. Personally, I find it difficult to keep track of my plants needs when I have them in too many different mediums. When everything is going smoothly it's not such a big deal, but during seasonal changes it's really helpful that they are all going through the changing conditions in the same way. Although someone could make an argument for being sensitive to the unique needs of such and such a Hoya, I don't think KQ is the fussy sort such an argument would apply to.

Because I have this policy I have transferred tons of Hoyas from one medium type to another. Some of them don't seem to react at all and others do take a while to get settled. But 'getting settled' is the exact right way to put it because they are never unhappy in the end. You might go through a season where your old favorite is a bit slow, but she'll come through with an extra bang in the season after that, I guarantee it. If it's what you want to do, I say do it! It will be FINE! And it's exactly what I would (and have) done.

And maybe your Hoya is looking very healthy for completely other (non-sandy-soil-related) reasons, like all the other things you do for it.

I traded some plants for a large mature Hoya carnosa several years ago. The carnosa came in very old compacted soil and was not in the best shape itself. I mixed up some new potting mix and that plant pretty much exploded in growth. The new growth was obviously from the combination of new potting mix and bright southern exposure light. I agree that your plant will always be better off in a new mix, not changing the potting mix will only cause a slow decline in plant health.

I think the easiest mix for most people to make up consists of easy to find ingredients. Good potting soil, large perlite, and orchid bark or bark from the pet shop that is sold for reptiles. When using bark it is best to soak it overnight with a drop of dish soap in the water. Not soaking bark causes the bark to draw moisture out of the potting mix and this can cause stress on newly repotted plants. There are many other mixes that you can try but this is a good basic mix that most Hoyas will do very well in. The mix should be quite coarse so roughly equal parts of soil and bark work well and then add about a half part perlite. If the mix is very light and open it will dry quite fast so I tend to add extra soil to allow for better water retention. Another way of slightly altering the mix to be more moisture retentive is to add something like vermiculite or chopped sphagnum moss. The same goes if you want a mix that dries faster, adding perlite, diatomite, or expanded clay hydroponic media or turface will help increase drainage.

GG is right on when she mentions evaluating the growing conditions of the plant. When you repot think also about the light the plant gets, is it getting enough? Think also about the watering schedule. If you notice that your house plants get a mineral deposit on the surface of the potting mix then you will have to consider that the water might also be causing problems.

Let us know what you decide to do and how it goes.

Mike

I re-potted all my hoyas earlier this year. There is a man from Vermont that grows hoyas for a hobby. I used his recipe for potting medium and let me tell you, my H. Cimmamonfolia is growing like crazy. My other hoyas are responding in kind, like my H. Schneii that I got a cutting from HI is ready to bloom in several times. I think repotting is good for hoyas after 2 or 3 years.

Tpie

Maybe you should try cactus soil or soil mix for self-watering pots. I believe they are sandy like the mixture you described. Then you can add those trusted chunky ingredients as much as you want to.
I must add that I live in Finland and our brands and mediums are different from those available to you.
Good luck with your favorite!

Thanks guys. So, none of you have had an experience with a plant that rejected new soil just because it was a very different type than the last soil it was in?

Nope. Never have.

We all sideswiped your initial question, so let me just quick get that out of the way.

Hoyas, like all other plants, do need to be repotted periodically. Not repotting a Hoya would be like never giving your kid new shoes. Their root systems outgrow their pots and their medium (in most cases) decomposes and/or compacts over time. They just don't have to be repotted as frequently as some other types of plants. Still, plan on repotting ever 2 years or so, longer if you are using mostly inorganic or slow-degrading materials.

How do you know a Hoya needs to be repotted? Well, with most people it's not an exact science (although it could be) but there are certain things to look for. The medium might have visibly 'settled' or no longer permit a normal drainage pace (this leads to the build up of salts/minerals Mike referenced above). The plant may have become root bound, with roots that circle around the bottom, or simply take up the entire pot, with little room left for dirt. Often you can tell just because the plant has become weaker or is growing less enthusiastically than it once did.

I understand your hesitance to "fix what's not broken" but in this instance, I don't think you need to worry that your compact won't grow just as happily or moreso in the chunky mix you have on hand. The only reason a Hoya would do worse in a dramatically different mix is if the new mix was a bad approximation of the conditions it was adapted for. If plants weren't perfectly capable of adjusting to dramatic change, none of us would be able to import cuttings from Thailand. >:P

In all the time I've been reading here the only situation where people find it difficult to guess whether a Hoya will "do well" in a dramatically different medium is when they are switching to semi-hydro.