some possible causes for bud blast are letting the plant dry out while in bud, drafts, or moving the plant while in bud (though I move mine all the time) But you could be guilty of none of the above and still have it happen

Gardensnail, are you referring to "buds" drying up and falling off BEFORE they flower? Or are you talking about open flowers drying up and falling off? If it's the latter, that's completely normal. Lacunosa flowers will dry up and fall off after only a few days (they are very short-lived...about 5 days I would guess). Not all hoya blooms last the same amount of time...some can last a few weeks, while others can last a few days.

Garbo They dry up before they are fully open sometimes. You can see in the picture some that have done it. I think ines99 is correct and maybe I let them dry out too much. It is a 2 inch pot with alot of perlite in the mix. Maybe too much pearlite. Thanks

That whole lacunosa is in a 2" pot? You could probably pot it up a bit, at least to a 4" or 6". I don't believe lacunosa has to be root bound to bloom, but if you don't want to take a chance, wait till it stops blooming or slows down and repot without disturbing the root ball too much, just set it in the new pot and fill soil around it. Then you won't have to worry so much about it drying out every 12 hours! I know the plant looks good now, but with some extra soil and moisture it will look better and lose less flowers in the long run.

Oh, I didn't see the picture before (I was at work and we can't see pics). Now I see the buds you're talking about. My Lacunosa is pretty big, and the it's in a 4.5" (diameter) and 3.5" (height) pot (COMPLETELY rootbound). I might pot it up also, just because the roots seems to be taking over the whole pot. But I am so hesitant to do anything while it's blooming (but when does it NOT bloom??).

My buds sometimes do the same thing that yours do. I'm not sure why. I keep my Lacunosa constantly moist (not wet, but always moist). I agree with Ines though...I think yours might be drying out too much. Not sure why some of my umbels dry up...guess it's one of those "for no good reason" things.

Here's some pics of mine:

ON KITCHEN COUNTER, ABOUT TO GET WATERED:

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ONE OF THE DRIED UP AND YELLOW UMBELS:

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Just to be clear, I was referring the the lower set of buds in the pic (the tiny ones). The other buds are about to open any day now...they just look yellowish in the picture.

Thanks Guys I think I will pot up a little and improve the soil so its not so dry. My leaves are a little yellow too when I compare to Garbo,s pic. Thanks again will send more pics