Sick dendrobium? Yellowing/ falling leaves, shriveled canes, and brown-ish leaf spot

[Joe.1]

Hello everyone,

I am relatively new to this board and I am quite excited to learn more about orchids and their proper care, maintenance, and treatment of diseases. I am also quite inexperienced with these little guys since I was just given a few of them about a month or two ago and now am trying my best to learn more about them. However, as all living things, some of my orchids are showing what I am suspecting can be diseases. One example (and the main subject of this thread) is my dendrobium mangosteen, which was given to me about 3 weeks ago. I immediately noticed that the two of the canes from this orchid were shriveled and not doing so well. I took the plant out of its old potting media and repotted in a clay pot with bark and pieces of charcoal. I also noticed that most of the roots were white/ beige in color, very few of them were green, although I am not sure if this is normal for dendrobiums. Some of the roots' velamen had come off so I proceeded to cut what I considered dead and left the other sturdy roots alone.

Freshly potted, with humidity levels fluctuating between 60 - 80% (with two fans as ventilation), artificial overhead lights, and indirect sun light through an eastern window, I started to notice some signs of concern on my plant. Some of my mangosteen's leaves were faltering as seen in the pictures below. I am thinking that this may be some sort of rot. Although, I cannot confirm. The pictures do follow a chronological order, so the very last one depicts a brown spot/ blotch on one of the top leaves. Curiously enough, (although I am not sure if relates to this) we had a front cold come in today and the temperature in the house dropped to 15 Celsius. I unpotted today after seeing this to inspect the root system, but the roots still look white/ beige just like in the beginning. There are no signs of new roots growing. To top it all off, I noticed the smallest shriveled cane had some black coloration on it... so that raised my alarm even more.

I water once a week doing a full soak of the media only. I fertilize weakly twice a month. The pot has excellent drainage and the media does go dry. I am quite confused because to my knowledge dendrobium mangosteen does not go dormant (please correct me if I am wrong on this assumption). So, I hope that by reading my story and looking at the pictures I am able to get some guidance as what approach I should take with this little guy or if this is any sort of disease or not.

pictures:

https://drive.google.com/open?id=0B3...zF1LVhTUGZOd0k

https://drive.google.com/open?id=0B3...FZBOF9ydlJ6UUk

https://drive.google.com/open?id=0B3...V80NXpsSWFCWlk

https://drive.google.com/open?id=0B3...ldZZnlnaUNKVnM

https://drive.google.com/open?id=0B3...2ViTnpiVTNCaXM

https://drive.google.com/open?id=0B3...DlOeHRlbHBWWm8

Thank you

[WhiteRabbit]

In my experience, Dendrobiums sometimes can drop some leaves after being repotted. The shriveling canes may indicate that more water is needed. Photos I found of this Den look to me like it's a Den-phal (from the Phalaenthe section of Dendrobium) - this type does not go dormant, or want a "rest". The few of this kind that I have had seem to do best when watered a bit before the potting media is completely dry, or at least just when the media has dried completely. Fresh bark in a clay pot may be drying quickly. I like to use skewers to monitor the moisture in the media / help determine when to water. Using skewers to determine when to water

[estación seca]

First, Welcome to the Orchid Board! We look forward to your future posts.

Your plant is still in quite good condition, and it should grow nicely with good care. I agree with Sonya it is likely a Dendrobium phalaenopsis hybrid. A minimum of 15C is no problem for these; they are fine even down to 10 or 7C at night, and perhaps lower, if the next day is warmer.

Some of your leaves have wrinkles, indicating not enough water getting to them. This can be caused by not watering enough, or by not enough live roots. Once proper watering resumes, it can take over a week for the plant to absorb enough water to make the wrinkles go away. If they are severe they will not go away. Wrinkled canes on this type of Dendrobium will not fill out. They are still functioning, though, and should not be removed until they are completely dry and brown.

The one leaf with yellow and brown spots in the first photo is on a newly developing growth. It might have sunburn, but inadequate water is more likely. Sunburn is normally on upper leaves.

One of the later photos shows a smaller top leaf with reddish margins. Reddish margins mean high, but good, light levels. I would guess your plant is now getting a good amount of light.

We can't see the roots. This kind of Dendrobium doesn't do well with always-soggy roots, but it also doesn't like being dry for very long. If your plant doesn't have adequate roots, it will need to grow more before it looks really good. Your relative humidity is good, which makes watering these easier. They also develop new roots more easily in high humidity.

Most people use the smallest pot into which they can fit the roots, and water frequently, taking care the plants dry between waterings. Your use of the skewer is a good idea. In low humidity areas people use larger pots. Your pot is perhaps too large for your humidity, but you can manage it easily with the skewer. Water the plant, then don't water again until the skewer indicates the center and bottom medium is dry. When the plant begins growing new roots, in addition to your normal watering, I would use a spray bottle to moisten just those new roots once a day. Or you could dribble a few drops of water from your fingers just onto the new roots. This will encourage them growing.

[Joe.1]

Thank you everyone for your responses. I really appreciate your input. Being a novice with orchids, I tend to freak out easily due to my lack of experience. I will keep an eye on this little guy and post a future update on its development. I'll heed your pointers and advice on the meantime. Thanks again!

[flexdc]

Joe,
This kind of Den is very tough. Down to 15c is no problem for them as long as they are not exposed to temps below 10 in prolong periods of time then they are fine.
If temp stays around 15 or so, they will not put out much growth or roots.
Warmer temps to around 20c will initiate growth again.

From the pictures, your plant looks ok to me. One yellow leaf is nothing to be concerned about. One caution though is over potting. These dens. like to be under potted.
You can do one of two things, either put it into a smaller pot, or I sometimes pour out some of the bark mix and fill it in with pebbles or broken pieces of clay. This way the medium won't stay wet for too long.
Again your plant looks good, the only thing I would change is the potting.

Andrew