Sick Dendrobium Nobile

[Tanya]

I am used to seeing orchids (except for Phals) displaying this kind of problem, yellowing, from the top down. This is all new to me specially for Dendrobium. The yellowing started at the bottom of the new growth slowly going up, the canes are still firm.

It had been raining since the middle of June, sometimes it stop for a day or two or few hours and orchids in plastic pots and on the floor outside never really had a chance to dry out before it rains again.

Could this be caused by too much water? But if it is so, would the roots rot first before the cane does? The roots on the surface seems fine.

This is one of the cane, the yellowing is still low at the bottom



This one, the yellowing had progressed almost midway.



This is the top view of the plant, decieving isn't it?

[catfan]

Hi Tanya-

The plant sure looks healthy...You may want to take it out of the pot and look at the roots....if there are lots of dead roots, you may need some fresh potting mix. When is the last time you had some new growths? My nobiles are sending out new shoots now. Most of mine are in baskets with sphagmum moss, though some are in plastic with bark, and some in clay with sphag.

Being able to figure out what you are doing wrong is one of those things that takes experience and careful observation, and will depend on your growing conditions. It may be time to repot...but most dens. do not like to be over potted, and do best when a little pot bound. I've been using a lot more sphag in unglazed clay pots (the clay wicks away the moisture) and baskets, and I think the roots have an easier time growing through the soft moss, but then again, my plants are in a greenhouse and get lots of air circulation.

Another thing I've noticed is that orchids like a little pruning every now and then...it stimulates new growths. Most nobiles will bloom from old canes that are still green, but if you don't have new growths your not going to have that specimen plant we all strive for. If the yellowing cane is the one without leaves, you may want to cut it off at the base...with a sterile blade...I wish I could be more helpful...

[Tanya]

Hi Catfan,

The two yellowing canes are the new growhts. I bought this plant last spring in bloom and with 4 new growths. I potted it into bigger pot once the flower faded. Everything were fine, new roots growing and then the rains arrived. It might be the rain, too much. I will unpot tomorrow and and cut off the yellow canes. That would leave me 2 new growths and the older ones.

[Gin]

Hi Tanya , the yellowing at the bottom is probably from being wet to long , or bent at sometime in that area , catfan is right on . If the roots have a problem it would be in the center of the pot . I have quite a few of the nobiles most are in clay pots and dry between waterings . If the cane it is soft and spreading I would remove it and seal the cut . If firm wait awhile , if it progresses especially toward the bottom , Chop it !
It is sure a nice looking plant . Gin

[Tanya]

Hi Gin,

I might lost all the new growths and one older one, or possibly the entire plant!! The problem with this is it starts at the bottom. I was gonna do the cutting today but found out that I have nothing to seal the wound so I have to wait until tomorrow, gonna buy the white stuff today.

[Gin]

Hi Tanya , I am sorry about the Dend. trouble . Know how it is , what I think happned is .
The larger pot and more mix , plus the rain . I know when I repot there are always some damaged roots . You can take a q tip soak it in peroxcide and apply to the cuts . be sure to keep the cuts dry , might move it indoors if it is the rainy season there . Less light than usual . Hope this helps a little . Gin

[Tanya]

Well, the deed is done. When I unpot I found out that most of the rotten roots are those at the bottom. Cut off 3 of the new growths. It is now indoors and there is nothing more I could do now but wait and hope for the best. Honestly, I don't hold much hope, its far more advanced than I thought (its them green healthy looking top that decieved me).

Thanks all for the inputs.