Lali....there are so many choices how to root that one could go nuts figuring out the "best" way. Some swear by the baggie method, others by the water method and while I have used baggies with the small leafed small stemmed species....or I have put a baggie over the pot where they ae rooting, I prefer soil. But not just any old soil.
Look at it this way: most Hoya are epiphytes. The seed finds a moist inviting crotch or notch in a tree and there it germinates. Once it grows up, the vines travel along and root to the surface (hopefully), especially if it encounters another warm inviting crotch in a tree where leaf litter, some moss and bird poop have made a terrific rooting place.
The roots, generally, enjoy air - not all 'sogged in". At least this is what I find. I used to use a mixture of peatmoss and perlite, but the peatmoss would get too dry too fast. Then I used a mixture of spagnum moss and pearlite wrapped around the stem losely and kept moist....with air circulation. Hmmm, this method worked really really well - and by the way, is the method that David Liddle uses (he wraps the stem in spagnum and puts it into a small pot with artificial soil in the bottom. This arrangement he keeps misted and moist and it works beautifully.
Needing to take a shortcut one time...no time to rinse the spagnum and go thru that routine, I used the potting soil I use for most of my plants - with no fertilizer added which I do for my rooted cuttings when/if I transplant. It is equal parts fine orchid bark or coir, #3 perlite, lava cinders and chunky peat (which is full of twigs and stuff). When wet I can squeeze this medium and it NEVER gloms together!!! I stick the cuttings in this mixture, keep them damp on a heat mat....and I do hundreds at a time. When we get the dry Kona Winds (hot and dry) I mist the pots on the heat mat when I remember and the greenhouse does have a fair amount of humidity. I lose maybe .05%. I have heard of people using pottery shards, wine corks chopped up, volcanic pumice....anything to aerate the medium Don't use red lava rock because it has too much iron.
I live in ideal conditions, granted! My heatmats are under 80% shade with bright indirect light. The mats go on when the ambient temperature goes below 73 deg. If I need more room on the mats, I take the bigger easy to root hoyas and put them in a shady area off the heat mats and they root just fine....
My feeling is that plants need/want to grow like they do, or closely to, how they grow in nature. Warmth (for most), indirect bright light, humidity and air movement are key....the airmovement (not drafts) being, I think, most critical.
Remember...this is just how I do it...doesn't mean it is the only way by any means.
:>) Carol
