Tiny Dendrobium keiki-Help with a root mystery
 

:hello
So back when I moved into my current house (about a year ago), I inherited a greenhouse from the previous homeowners. In that greenhouse sat a mystery plant-it looked like a mini bamboo plant. Turns out-it was a Dendrobium plant (possibly a Den. Phal-definitely not a nobile-type).
https://st.hzcdn.com/simgs/04d2dc810...ome-design.jpg
It was in horrible shape-it had a huge mass of dead/rotting roots and all the canes were beginning to yellow. There were two small green sections. After reading some posts online about people growing Dendrobium keikis from cut canes, I decided just to give it a go and see what would happen.

One of the canes eventually yellowed, but on the other one...
https://st.hzcdn.com/simgs/f7e28d820...ome-design.jpg
(Ignore the potting soil-I was a complete orchid noob then :P) A green nub was growing!

A few months later:
https://st.hzcdn.com/simgs/583284440...ome-design.jpg
A tiny keiki was growing!
After finding out that orchids hate soil and needed a medium which provided plenty of aeration, I switched the growing keiki over to some sphagnum moss. Some tiny roots were a bit stained brown, but new ones were already beginning to grow. A few weeks later:
https://st.hzcdn.com/simgs/f062fc760...ome-design.jpg
https://st.hzcdn.com/simgs/5e72cc4b0...ome-design.jpg
It had eight roots, all with healthy growing tips. I thought it was going to be smooth sailing from here.
Turns out I was mistaken.
As winter arrived, root growth slowly came to a halt. I attributed that to the decrease in sunlight. Some white stuff (I think it's salt buildup from my water supply) began taking over the moss, so I repotted the keiki with a fresh batch of moss.
https://lh3.googleusercontent.com/-4...2016-10-17.jpg
However, as we approached the middle of winter,
some of the longer roots began going brown.
https://lh3.googleusercontent.com/-y...2016-12-13.jpg
(You can see a greener root compared to two brown ones)
Eventually they died-I gently pinched them to make sure-all the brown ones were squishy.
Meanwhile, the keiki lost two of its smaller leaves. The two biggest/newest leaves remain to this day. The newest leaf was still closed and growing at the beginning of the winter, but has opened a tiny bit since the beginning of March (the top part is still closed.) I have no idea why the longer roots died-I'm assuming it was a result of the water being too hard.
I bought a gallon of distilled water to use with the keiki, and so far it's been working okay-no more dying roots.As of today, it has at least three roots still alive-they green up when watered. However there are still some salt traces on the moss-should I repot the keiki again to some fresh moss or leave it alone? I'm afraid repotting it again will stress it out too much.
Here it is today-
https://lh3.googleusercontent.com/-z...2017-04-02.jpg
The two smaller roots in the picture are alive-the bigger one going downwards is dead.

What can I do to help this guy along? Right now it sits on a windowsill facing south. I water (I pour water into the tray and let the moss soak it up) it whenever the moss dries out completely-about once a week or so. I have not fertilized it at all. The mother cane is still green-just a bit shriveled, so I assume it still has some nutrients for the keiki. The humidity in the room is around 35%. Temperatures range from around 67*F at night to 74*F during the day.
I would really like this guy to survive-it would be amazing :)
Thanks in advance!
ETA-the remaining roots have not resumed growth yet even though days have been getting longer. No growing tips are visible-just the tiniest green dot in the center part of where the root ends.

I could be wrong (as usual) but it looks and sounds to me like you've somewhat overwatered the keiki. In your pics the medium looks exceedingly wet. This can lead to root rot. Allow the medium to get JUST dry before watering again.

Den phals don't like to be too wet so, I agree with John. The fact that you have gotten this far is amazing. bil is an expert at this method, maybe he will weigh in.

That's the thing-I do let the moss go completely dry before watering. The roots also get plenty of exposure to air. :hmm:dunno:

Should I maybe pour less water each time I water? I pour enough to reach the bottom of the plastic container the keiki grows in. I then leave it there for it to slowly evaporate-my thinking is that doing so will provide it with some more humidity just around the keiki.

It also grew a new root just as the others were beginning to die off, but stopped growing just like the others did. I thought it was the salts that dried up the root tips-could it be too much water somehow?

I'm thinking of setting up some kind of mini greenhouse around it, although I'm afraid it'll get too hot in the middle of summer.

I also have a tiny cup (tiny enough to fit in my hand snugly)-maybe (if I do repot) potting the keiki in that may be better? I can create holes along the sides if needed.

Oh dear. It always worries me when someone says that...

I think that denphals are about the most indestructible orchids there are that I have tried.

I think that jkofferdahl has it bang to rights, as does Dolly. These plants like their drink, but they really aren't happy being sopping wet.

Mine do best in fine bark and nothing but, and they like it really, really shallow, so it dries fast. I think mine are in 2" of bark in a wide, shallow 'pot'. That's a bit dry for a struggling one tho, so what I used to do was to take the whole cane off the plant like you have. (You get far better results than when you take the keiki off. For some reason a baby on its own, even with good roots just sits there and does nothing for me.)

So, I used to take the cane, and lay it horizontally on a thin layer of sieved fine bark, with a small amount of sphag moss wrapped around the emerging roots, then cover it with fine bark.
(I wouldn't fill the whole pot with moss, as I don't like to save a plant to then change the medium. I think that risks setting them back a bit.)

I would then treat it exactly as if it were a healthy plant and water it 3 times a week in summer. I do think having very pure water helps, I use RO and very weak fertiliser, about 25 ppm N and very low P&K. After all you are looking for growth, not blooms.
I was given a whole lot of thrown out Den phal canes by a garden centre here, and in any other type of plant they would have gone straight onto the compost heap, but I saved all bar one.

How fine should the bark be? Could the small leftovers in the orchid mix bag work (I use Better-Gro special orchid mix)? I don't want to get it too fine for fear of suffocating the roots.

Unfortunately this isn't doing much at all for the humidity but it's soaking the roots, allowing them to develop rot. Sphagnum can seem dry at the top yet when a layer of water is underneath it wicks it right up and into the roots. By using your method, unfortunately, your plant is never going to grow healthy roots. So you've essentially just described exactly what's causing the problem for your orchid. I would worry a lot less about humidity and focus on allowing the roots some dryness. If you've not punched a whole bunch of holes in the bottom of the container the plant is in then the problem is going to persist. Soak the sphagnum when it's completely dry, allowing the water to run through the holes in the bottom. Believe me, the sphagnum will still get plenty wet, but once the water stops running through, air will begin to find it's way in to the roots, and the sphagnum will begin to slowly dry. LET IT. As Carol pointed out, this particular type of orchid is averse to too much wet.

Good point

What I do is have two sieves. One is very coarse, and is big enough to let everything thru bar the 2" bark I like for phals. Then I re sieve the remainder to remove all dust and fibre.

The coarse mesh sieve is 3/4" mesh and the fine sieve is 1/4"

I'm not too sure if you understood how my setup works-let me try to explain it again :blushing:
https://lh3.googleusercontent.com/-z...2017-04-02.jpg
So when I moved the keiki into its current plastic container, I took an empty strawberry box, (kind of like this, including the holes at the bottom)
http://1.bp.blogspot.com/_r9q3xc7DG5...0/IMG_2542.JPG
washed it out, filled with some sphag that had been soaked for a couple hours, then set the keiki in. I then put the container in a black plastic take-out tray. When ever the moss dries out, I pour a little water in the tray and let the sphagnum wick up the water. I then leave whatever's left over in the tray itself to evaporate.
Should I continue watering this way? I pour just enough water (into the black tray) so that the water barely touches the sphagnum.

My advice would be, pot it up as described in fine bark with a small amount of sphag around the roots. They don't seem to like to much water, and certainly not all the time.
It is as tho the roots need to dry a bit to make them work.