Dendrobium with yellow leaves a few follow up questions

[Stefan Petersen]

Thank you so, so much for your advice. It was also really helpful, that you helped me determine the correct species. It made it easier to look up new information. Some of it made me a little confused though:

The roots on the top are they aerial roots? I have been watering it from the top and wondered if some water might have collected and soaked the aerial roots in a little puddle, because the bulbs are almost shaped like a little bowl. So I might have overwatered it from the top.

And last but not least. You gave me some good advice not to cut anything. But I am worried that there might have started some rot in the roots, and some people write that rotted roots should be cut off immediately. Are you sure, I should just let them stay in the pot? I think you are right that it might be difficult to determine of roots are rotting or not.

[Roberta]

I have seen the advice about cutting rotted roots... and have seen a lot of the sad results on this forum. If there are lots of good roots, trimming the bad ones is OK. But even a bad root is better than no root - even if the velamin (the outside coating of the root) is bad, the core of the root can still hydrate the plant, though not as well as a good new one. Also, even a less-than-wonderful root can serve to hold the plant in the pot. While it is growing new roots, it is very important that the plant be held firmly in place (since wobbling can damage tender new root tips and cause them to stop growing) That is really hard to accomplish without at least some roots.

The roots on top are, indeed aerial roots - there really is no difference between an aerial root and one in the pot other than their location. However, a root develops for its environment and tends to not adapt well to a change. So an aerial root moved into the pot will eventually die. BUT in the meantime, it's a good root and will help the plant while it is growing new ones (which will be adapted to the pot... hence the advice to repot, if possible, when new roots are just starting)

Since you do have some good roots outside the pot, if you trim the really bad ones than the plant still has a source of hydration. Looking again at the photos, the medium is likely quite bad. So it would be worth taking the plant out of the pot and assessing the situation. For removing bad roots, rather than cutting, I would suggest just pulling with your fingers. Anything that comes loose easily is not doing anything useful. Then rinse off the rootball under the faucet. That will remove most of the material that might be really rotten. Repot in fresh bark, coax those aerial roots into the medium as you pot it. Then, there will be lots of air in the root zone. Watering from the top is fine. Just be sure that it drains after watering. With fresh bark, you may be watering every 2-3 days, and that is fine - the problem was not too much water, it was lack of air.

[estación seca]

I don't cut roots. I can't tell which are really dead. One of your photos shows you holding the plant out of the pot. The roots look fine to me.

Most plants sold in markets are ready for repotting when sold, because they've been in that container/medium for about 2 years. Normally I suggest people not repot Dens until they see new roots forming. But you've already unpotted it, and this kind of Den is a reliable and vigorous spring grower. So now would be time to repot. Use medium bark or LECA; shake off as much old medium as you can, but don't be meticulous; wash the old pot and use that, since it looks like the appropriate size. Dens typically do well in pots that just hold the root mass. Resume watering immediately.

[Roberta]

I forgot about the photos where you already had it out of the pot. Yes I agree... don't cut anything. It looks fine. Just be patient... orchids don't do anything fast. Progress is measured in months or years, not days.

[Stefan Petersen]

Once again. Thank you so, so much for your help with my precious heirloom. If you ever happen to come to Denmark/Copenhagen I will definitely want to give you a hug and buy you a good lunch

I have taken another look at the top roots. What I suspected was rot is perhaps not that at all. Eventhough the roots are black and brown they are very hard and dry and not mushy at all. They feel hard, almost like they are petrified. It almost looks like there was a small fire in the roots, because of the black/brown color (I will show you some picture zoomed in at the roots). I wonder why they look like that? I can’t remember if the roots always looked like that since I inherited from my family member or if it happened in my care.
I was afraid I might have damaged them by watering them from the top with a watering can since the den fills out the entire pot, so I had to pour it over the roots where the bulbs almost form a bowl, since it is not possible to hit the medium. Is it possible that I could have damaged the aerial root by watering it from the top and hitting the roots?

I repotted the den three days ago in bark since the bark I planted it in in January may have been too tight (I did it right before I wrote you the first time. The pictures I attached was with the old medium). I might have used too much and made it too tight, since the den seemed to pop out of the pot every time I watered it in a waterbath. So I think you are right that there wasn’t enough air. And the yellow leaves have only just started to come after I replanted it in january..

There are some old bits of medium that are two years old (from a previous repotting), and these old bits are tangled into the roots. I couldn’t get them out with my fingers without tearing the roots so I just let it be in the roots. You recommended that before repotting it, that I should rinse it under the faucet to get old bits off. Should I still do that now that it is repotted or would it stress the plant to be picked up again?

I repotted it just before I turned to your help. But at that point I was unsure if I had kept it in too much water/drowned it, cause that was what google said too much water could make the leaves yellow. So I waited til the day after replanting (and your replies) before watering it. Which means I repotted it Tuesday and watered it Friday. In two days the pot went from 399 grams (just after the watherbath) to 363 grams today, (unfortunately I didn’t measure it yesterday) and when the drop in weight stagnates I should water it again, as a measure to figure out when it is almost drying out. Right? I think that might be a good idea since the conditions here in Denmark is a bit different. Our min/max temperaturs in May are 7/16 C goes up to 13/22 C in July and drops to 10/18 in september.

I was told by one expert (but also very grumpy and uninformative) that I should let the den stay in a bright place but without direct sun til september/october here in Denmark since the sun is up for 17 hours doing the summer (I don’t have an east or westbound window).

Once again, thank you so much for your help.

[Roberta]

DEndrobiums are tough and resilient - with sufficient water, I think that your plant will recover fine. Just be patient. Wrinkled canes won't become smooth again, but new growth will be fine. It just takes time.