dinema/encyclia polybulbon: half-closed leaves and possible sheaths?
 

hi all, the leaves on my Dinema polybulbon have for some reason never opened up all the way - instead of unfolding, they've stayed partially stuck together on several pseudobulbs. is this is a result of underwatering? also, i've noticed a little sheath-like thing between the two leaves on some of the pbulbs. having never dared to dabble in Cattleyas and the like, I'm not sure whether this is a sheath or just an underdeveloped/vestigial leaf. which one is it? thanks!

ps: the photos are taken with flash on my iphone, so i hope the quality is still ok! :)


edit: fixed orientation of images

some background on this little guy:

it happened to be the subject of my first (and only) attempt of mounting. i learned that I am not to be trusted with mounts... I now keep all of my plants in pots (the orchids are more tolerant of under-watering that way :D ). anyways, long story short, i received it with one active lead, but the lead died due to underwatering. i felt guilty for a while until I noticed that it was sending out new leads from 4 pseudobulbs! of course, i've learned my lesson, but i think the resilience of orchids is just amazing. and now it may (hopefully) bloom this year. :)

I think you're looking at sheaths... for what it's worth, mind has historically bloomed in the January-February timeframe, so you're getting close.

Hard to say here. I can say that I have a couple of catt-type orchids - miniature type, that sometimes have new leaves stuck together. Maybe glued shut by something or perhaps just some sort of suction/vacuum effect between the two flat leaves. Interestingly, just running finger nail (like letter opener) along the stuck section often results in the two halves popping open. The leaf might not open all the way (after becoming unstuck), but better than stuck I guess. The orchids themselves are just fine - produces nice flowers all the same.

Not sure what it's due to - low humidity, or a trait - or something else. I'm fine with it though. I actually quite like making the leaves pop open whenever I get the opportunity. It's kind of fun doing that hahaha.

one of the sheaths dried up... that's not supposed to happen, right? am I not supposed to get water in the sheaths or something? :(

Mine gets overhead watering, and the leaves opened normally, Buds are emerging (I expect a nice show in a couple of weeks or so). I know that some of the Mexican laelias (like anceps, autumnalis, gouldiana) tend to have petals stick together - overhead watering (where the buds get wet) seems to help those open normally (softens the sticky sap that tends to stick things together) So, far from being something to avoid, water on the sheaths (and new leaves) may actually be what the plant needs. Once flowers are opened, keeping them dry (especially when cold) makes them last longer and avoids botrytis spots) but they may need to open first.

Plants need hydrostatic pressure to plump up. Collapsed leaves, pleating suggest insufficient water uptake..

does this plant need more humidity, then? because I've read/observed myself that this species has very shallow roots, which sometimes don't actually penetrate the medium. the medium in this pot is almost always wet because minimal absorption occurs and it seems most of the roots are in the air or just barely contact the moss. how would I increase water absorption?

Mine is mounted. Those little roots just barely hang on. I water it daily with the rest of the mounted plants. So it basically needs daily watering, make sure that those air roots get watered. Semi-hydro in a relatively shallow pot might be a way to go, at least there's a constant supply of humidity that way. If you have the setup to maintain a mounted plant, that's really what it wants... it is a creeper/mat former. Another approach might be to tie it to the outside of a terracotta pot, with sphagnum inside the pot. (Keep the sphag wet) Again, a way of getting constant moisture to the little aerial roots and letting the plant wander where it wants to go.

Thanks! For a serial underwaterer, would you say that the terracotta mount could work? I've never tried s/h and am a bit reluctant to let this plant be my first test subject. :)

---------- Post added at 07:24 PM ---------- Previous post was at 07:16 PM ----------

also, would you say that the evaporative cooling from the terracotta would chill the roots? actually that's a concern for a bunch of my orchids - the unglazed clay pots all feel so cold to the touch.