Dendrobium in danger: I think my dendrobium victoria-reginae is in trouble

A leaf turns yellow then falls

     The signs were there months ago, when a new root tip suddenly and inexplicably rotted away.  My dendrobium victoria-reginae is suffering.  After the loss of the small new root, I noticed that the top of the newest growth seemed deformed and dried out.  Meanwhile, of all my orchids, this one was the only plant to lose leaves after a dry period over christmas break.  Something is wrong with this orchid, and I am not sure what I need to be doing to fix it.

dried out top of new growth

     

    Earlier this week I decided to unpot the orchid and check on the health of its roots.  What I saw was discouraging.  The same multitude of roots which were green and healthy 2 months ago were now mushy and mostly rotten.  The pitiable state of the roots explained the weak and shrunken appearance of the plant.

     Although all but the first 2 inches on the central root seemed dead, I decided to be conservative in trimming back the roots.  I only cut back the most obviously mushy/rotten roots.  Since the dendrobium seemed to have so few good roots left, I didn't want to risk cutting off any roots which might still be functional.

dendrobium roots after trimming the most rotten tips

     All the roots in the above picture were green and healthy just two months ago.  After trimming away the deadest of the dead roots, I repotted the orchid into the smallest pot I had, reusing the original potting media.

     I am uncertain as to why my dendrobium victoria-reginae has faltered in this way. I had followed the typical instructions for growing this species of orchid: grow on the wet side under lower light. But all the signs indicate that something is very wrong with my current culture conditions for this orchid.  My first suspicion (and the usual culprit in orchid decline) is that I have been overwatering.  From now on, I will let the pot dry out more, so that I am treating the orchid more like I treat  my paphiopedilums.  (In fact, I haven't watered the orchid since repotting on tuesday). Also, I moved the orchid to a slightly more shaded location on the growth shelf.

two new root tips

     Fortunately where there is life, there is hope.  And I caught the trouble with this orchid relatively early (though I should have been more suspicious 2 months ago when the first root rotted).  Although this orchid will never grow back the leaves it lost, it is not yet at deaths door.  The picture above shows 2 new root tips poking out of the base of the cane.  I had actually only noticed one to take the picture, but when examining the photo in close-up I noticed the nub of the smaller root on the right.

     Of course, if the original problem remains unfixed, these new roots will soon perish just like their predecessor did.  An orchid can only put out so many new roots to die before it exhausts its energy reserves.  However, if a slightly dryer growth condition is the key to preventing further rot, then these two tiny root nubs can flourish and help the plant recover.  I'll be keeping a very close watch for any signs of either further deterioration or of improvement.