Dendrobium woes - need some help with yellowing leaf tips

14 years ago

Hi everyone,

I'm having some problems with two of my dendrobiums. As some of you know, I really enjoy growing the formosae/nigrohirsute dendrobiums. It's now my 2nd season growing them, and while I'm getting fatter/taller canes compared to previous years, I'm also noticing some strange leaf yellowing problems. I've noticed with dendrobiums in general that the 'normal' leaf drop occurs by which the entire leaf turns yellow, then dries and drops off. However, what I am observing is a yellowing from the tips, followed by a drying, that progresses from the tip down to the base of each leaf. This also commences from the bottom of the cane up.

No rot, just yellowing and drying. I fertilize way too infrequently for this to be fertilizer burn. Regardless, below are my conditions and some photos...I'm really hoping someone out there can help me out. These are two of my favorite plants so I'd appreciate any feedback whatsoever.

Plants in question: formosae dendrobiums

Dend Peng Seng (tobaense x cruentum)

Dend Frosty Dawn (dawn maree x lime frost)

Conditions:

8" from T5 lights, 16 hrs a day

Grown in a tank with higher than ambient humidity (vague, yes I know)

75-85F

Potted in 3" plastic pots with course fast draining coconut chunks, charcoal, and hydroton pellets.

Watered once every 3-4 days, media is allowed to NEARLY get dry in between watering. (at the beginning of the summer, I let them get bone dry for a day in between waterings...that was when I started seeing the yellowing, so I upped the watering schedule...but the symptoms are still progressing)

Plant conditions:

In general, roots seem very robust - both plants have tons of roots, growing both into the pot and out of it. All roots have green tips, all look white and healthy. Both are quite root bound, to the point where I could risk some damage if I were to unpot them. It does concern me a little that there is little to no root growth out of the holes at the bottoms of the pots...nor can I see many roots through the holes at the bottom.

{{gwi:192738}}
This is the plant today - it's been in bloom 2nd season now, for 3 months, on the second cane. It is currently maturing another cane which I believe is near to mature. You can see the severe dying back of the leaves...originally I attributed this to a natural annual leaf drop. However...

{{gwi:192739}}
the newest cane is now showing some leaf tip yellowing which scares me.

{{gwi:192740}}
This is Frosty Dawn...started showing the yellow leaf tips about a month ago.

{{gwi:192741}}
Lots of roots all over the place. Some roots look like they stalled and then came back to life...not sure why.

{{gwi:192743}}
The new growth on the frosty dawn...lagging behind the peng seng but it looks good so far. You can see both what I suspect is a natural leaf drop (the entire leaf is yellow) as well as the strange leaf tip yellowing in the background.

I'm not sure if humidity is an issue...I suspect not, because I have a dawn maree which is a parent of frosty dawn, and it's growing happily on my windowsill with no yellowing at all.

Any ideas? I've exhausted all my options so I'd really appreciate any leads.

-Calvin

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Comments (12)

jane__ny
14 years ago
last modified: 9 years ago
Strange, Calvin. I would almost guess too much light or heat on the leaves. How long have you had these plants?

Jane
littlem_2007
14 years ago
last modified: 9 years ago
Hi, I think that Jane is right. i put my dends outside and it started doing the same thing. after i moved them to a more "shaded" area, the yellowing has not continued. good luck with them. the flowers are gorgeous. wish i can flower mine.
sue
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smwboxer
14 years ago
last modified: 9 years ago
I had the same problem with phals and T5's. They were about 8" aways from 4 T5's and all started to yellow. I've since removed one bulb and have a fan running that moved the air from one end of the fixer to the other. I've noticed improvement.
petite_orange
14 years ago
last modified: 9 years ago
Leaf-tip dieback can also be caused by excessive temperatures, perhaps more a problem in my Gulf Coast area, but your lights might generate more than these intermediate-growers like.
I have a lot of this in my orchids this summer (not just Dendrobiums), and it has been exceptionally hot, even for us.
And dry.
If I had *time* to overfertilize, I am sure that I would!
Regards - Nancy
xmpraedicta
Original Author
14 years ago
last modified: 9 years ago
Thanks for all the ideas. Jane - I've had them for about a year and a half now

I think you guys are right - I will try to setup some fans to dissipate some of the heat, which is one thing I haven't tried yet. I also moved them slightly further from the lights...the leaves aren't too pale in color, so I wonder whether it is too much light. They have also been in that position for a while now, so it seems strange that burn would happen right now...plus, the pattern doesn't look like burning.
serenasyh
14 years ago
last modified: 9 years ago
oops sorry to intrude on this post, but I just had to say what a gorgeous, "exotic" and beautiful blooms you have! I love the contrast with the rich green in its young stages and its mature bloom with the arresting orange...Gorgeous, gorgeous both of the blooms! wowza...

In the rose and Asiatic lily world, we always see this intense browning and yellowing, in fact had I not read others' responses I would have said huh? how can thrips be near an orchid since orchids are kept indoors??? The garden pest thrips will always decimate leaves just like what you show- always working on the other edges first-the exact same browning and patches. But once again we're talking orchids, so I am learning tons of new things about heat and light balance here.
xmpraedicta
Original Author
14 years ago
last modified: 9 years ago
Thanks serenasyh :) they're two great plants...all of the dendrobiums in this particular section have interesting orange/red with white/green color combinations, making them very striking. They also have little black hairs on their stems which is quite interesting.

Thrips do grow indoors...maybe it's a variety of an indoor thrip? I had an infestation 2 years ago which was awful. Repeat treatments are required to get rid of them. They seem to manifest a bit differently in orchids, though - there's a white/yellow discoloration that appears in patches and looks almost like it can be scraped off, but it can't. There are also little black spots of droppings all over the place ... it's horrible.

Glad to see your cattleya is blooming well in your other pic. From the photo, the light looks quite good which is one of the most important things to keep in mind. In terms of heat/light, usually the rule of thumb is that if the leaves are not warm to the touch, they are okay. If they are warm to the touch, you could be getting too much sun. This is just a guideline though...the leaves on my dends are not warm at all.
highjack
14 years ago
last modified: 9 years ago
Calvin I don't think it is a light issue meaning the leaves are hot to the touch but the lights are too hot for the plant. It is probably heat stress not sun burn.

I don't have the cruentum but the tobaense is a cool moist grower. If it were my plant(s), I would treat the plant like it is mounted and step up the air circulation. It is possible the only viable roots you have are the ones you see wandering over the top of the pot. You could also pop the plant out of the pot and not have to guess what you have in there.

Brooke
serenasyh
14 years ago
last modified: 9 years ago
Calvin, on second thought, maybe you might have to do some precautionary, just-in-case hanging of yellow sticky traps against any thrips possibility...Thrips are nearly invisible to the naked eye and they don't! leave black droppings... I think that what you described as your thrips infestation 2 years ago was a type of aphid called citrus blackfly...They leave behind casings of very tiny brittle black crustings and white patches and yes! they are also from Asia in origin so if you have Asian orchids, you could have gotten that infestation... Thrips damage on lilies and roses look exactly like yours...They leave bright yellow markings almost always at the bottom of the leaf and spread upward (who knows why they like this configuration of eating) that turn to brown...Thrips damage look like "burns". My lily buds and leaves looked exactly like your photos. Huge spreading patches of brown. You can try what others suggested, but might as well hang a few yellow sticky traps just in case.

P.S. on an unrelated topic, if any one of you orchid people are using a pesticide called Sevin, don't! Sevin is highly toxic to bees and will wipe out entire bee colonies because it is a poison that is carried out to the hive. Sevin is outlawed in Europe, but sadly is the 3rd most popular insecticide in the U.S.
xmpraedicta
Original Author
14 years ago
last modified: 9 years ago
I think there may be many types of genera that fall into the 'thrips' category. Check out this site and look at 'damage to orchid' - I got someone from the university to check my plants and they're pretty sure I had banded greenhouse thrips (Hercinothrips femoralis) - they seem to attack dendrobiums and essentially I had what you see in that photo - webs of white. Yeah, these were very small, barely the size of a pin head. Maybe it's a different variety from what attacks out door plants?

I do spray down with safers insecticidal soap regularly but I checked out some of the leaves under the microscope at work just to be sure and it seems clean.
serenasyh
14 years ago
last modified: 9 years ago
thanks for the link Calvin. I am always learning so many interesting things about orchids and now about their arch-enemies, lol! And yes Safers insecticidal soap is a really nice product too.

Anyway here's wishing you much luck and success in your orchids' recovery. Let us know how the puzzle comes together and if any of the changes you decide to make for it are working. I would love to learn more things about the care of your Dendrobriums. It is a lovely and has so much character in its blooms
ifraser25
14 years ago
last modified: 9 years ago
Calvin, this is a puzzler. It does look very like fertilizer burn. I wonder if something, maybe the stress mentioned by others, could be interfering with your plant's metabolism. Look at those roots - they are fat and obviously full of phosphorus. Excess P causes exactly this kind of leaf burn. I would do as you say and try and reduce temps a bit esp. at night. Most Dends like cool nights. But as a precaution I would just use pure water for a while then nil phosphorus to see if you can get rid of the excess P. - Ian.

Dendrobium woes - need some help with yellowing leaf tips

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Dendrobium woes - need some help with yellowing leaf tips

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