Yellowing leaves on Dendrobium - Orchid Board

Paul Mc · #1 12-19-2010, 10:32 AM

I have a Dendrobium Salaya Soft Blue whose leaves are turning yellow. I recall that it has always done it this time of year, but I'm a bit concerned for two reasons.

#1.) It's been blooming like crazy since August and still has more flower buds to open yet. It has never done this before in the 5 years I've owned it. It usually flowered for me in the spring. It is quite mature now I'd say, so maybe that has something to do with it blooming twice in a year, although I did notice mushrooms this summers which means the medium probably has a lot of nitrogen (is this correct?) now which may be inducing the blooms.

#2.) A lot of the leaves that are turning yellow and dying off have bumps on them. Not damaged looking per say, just really bumpy. Plus half of the leaves falling off are on the bottom of the canes, while the other half are turning yellow from the top of otherwise healthy canes.

Any thoughts? Is this just a result of it being more mature so I'm noticing it more this year?

smweaver · #2 12-19-2010, 02:08 PM

Can you provide a picture of the "bumpy" leaves? Perhaps it has a scale insect infection (they somewhat resemble barnacles, but can easily be rubbed off with your finger or a cotton ball soaked in rubbing alcohol).

I would cut all of the flower spikes off, give the plant a little less light, increase the humidity and let it dry out thoroughly between waterings (better to rehabilitate a sick plant than to allow it to bloom for an extended period of time at the expense of its health).

Paul Mc · #3 12-19-2010, 02:23 PM

Sure, here's two pics I just took. I've already reduced the watering quite a bit (once every 2 weeks), and increased the humidity around it by keeping the tray full at all times (it disappears quickly).

I don't think it's scale as the bumps are green and appear to be part of the actual leaf (they won't move with scratching on them).

smweaver · #4 12-19-2010, 04:23 PM

Paul, it may be spider mites. Try wiping a clean white cloth or facial tissue across the bottom surface of the leaf to see if any discoloration occurs. If that doesn't show anything, however, I'm at a loss as to what the problem might be. Hopefully someone else who's got more experience with the type of dendrobium hybrid you have will give you some worthwhile feedback. Good luck.

Steve

CTB · #5 12-19-2010, 06:05 PM

Did it get caught in the cold, or has it been planted in spag too long? Looks like too much water to me.

Paul Mc · #6 12-19-2010, 06:32 PM

It got into the upper 50's when I brought it in about 2 months ago, and the problem only recently started (2 weeks or so). That's why I was wondering if it was just natural or something else. I do remember it shedding some leaves last year, but it has never flowered like this before - ever, and especially in the fall/winter!

It appears that all the flower stalks have emerged this time around, there aren't any others developing which is a relief.

It has been potted in the same medium for almost 2 years now. I intended to repot when I brought it in but I didn't want to disturb the blooming cycle or risk damaging it during bloom. I think I probably should have changed the medium in the summer when I started noticing a few mushrooms, lol... Oh well, hindsight, right?

smweaver, I tried what you said and the clothe was clean so I guess it's not spider mites. Should I spray 90% isopropyal alcohol on it just in case?

CTB · #7 12-19-2010, 08:05 PM

I think you should repot it, carefully while it is in bloom. By the time it is finished blooming it may be too late. I have repotted during bloom and it has been ok.

smweaver · #8 12-20-2010, 07:36 AM

Paul, I wouldn't spray it with alcohol, which might end up stressing it. Go ahead and repot it as Carol suggested. Oddly enough, underwatered and overwatered plants sometimes exhibit the same symptoms: dessicated leaves and pseudobulbs, prematurely yellowing and dying leaves, etc. If the medium has decayed and most of the roots have been lost, that would definitely contribute to what you're observing.

Paul Mc · #9 12-23-2010, 08:52 AM

Update: I repotted it as suggested and found out that on this particular orchid I had never removed the chunks of bark that it was in when I bought it. I've had this orchid for about 5 or 6 years, so needless to say it was a mess since the roots had grown through the broken down bark. For the most part, the roots looked absolutely fine, but the broken down medium was extremely soggy.

I made sure to rinse the roots clean, used a little bit of listerine to clean them, cut off one small dead stump that had started turning brown at the base, divided the massive clump as there was a bare spot in the middle (like a fairy ring of toadstools,lol...) and repotted in fresh medium. I also removed all yellowing leaves so the plant wouldnt spend more time trying to heal or get rid of those leaves.

Thanks everyone. Hopefully that will do the trick!