Why are leaves yellowing on my Dendrobium biggibum?

[nidiasophia]

HI,

I have a Dendrobium biggibum (or cooktown as they call it) orchid that is growing a new cane. Everything appeared to be ok, but I am noticing now that leaves on the new cane are turning yellow and falling off.

The problem is that it is not the leaves at the bottom, but leaves closer to the top that are turning yellow and falling off. See the picture for details.

Right now I have the orchid on a windowsill in my office that faces southwest and gets alot of sun.

Any advice?

Thanks

[dounoharm]

hows the air circulation? its not in a draft is it? or is it getting enuf light? i wouldnt worry too much if it is just the one leaf.....gl and hoping maybe someone else will have more information for you....

[nidiasophia]

Originally Posted by dounoharm

hows the air circulation? its not in a draft is it? or is it getting enuf light? i wouldnt worry too much if it is just the one leaf.....gl and hoping maybe someone else will have more information for you....

Thanks for the reply....the air cirulation is not that great - I dont have a fan or anything running in the office. The weather is getting better so I just put it outside.

[vcuchick]

Nidia-

I have a couple of those- they're deciduous so they do drop leaves each year. Mine have also dropped some leaves in the past few months...as for it being the new cane, perhaps it's a light or air issue. try buying a small fan at Target/Walmart and set it a few feet away and see if that helps. That leaf won't come back, but perhaps it'll keep the others around. What's your watering regieme(sp?) like? What kind of water? how often? fert? how often? mine grow in an east facing window. How long have you had it? I posted some pics of mine for you to see, mine are the compact variety since I have less growing space.

[nidiasophia]

Originally Posted by vcuchick

Nidia-

I have a couple of those- they're deciduous so they do drop leaves each year. Mine have also dropped some leaves in the past few months...as for it being the new cane, perhaps it's a light or air issue. try buying a small fan at Target/Walmart and set it a few feet away and see if that helps. That leaf won't come back, but perhaps it'll keep the others around. What's your watering regieme(sp?) like? What kind of water? how often? fert? how often? mine grow in an east facing window. How long have you had it? I posted some pics of mine for you to see, mine are the compact variety since I have less growing space.

Thanks for the response:
*I water once a week
*I fertilize at quarter strength with every watering (skip the fourth watering)
*I water with tap water
*I have had it almost one year.

[digitalgate]

I would bet it is insufficient sunlight plus too dry.

[kmarch]

nidiasophia, I dont' think your dendrobium is the species Den biggibum. It looks more like a biggibum hybrid, aka a phal-type hybrid (not to be confused with phal as in phalaenopsis they've nothing to do with one another). The plant habit of your plant just doesn't look like the species biggibum to me.

With that in mind, go to AOS | Members Only Area and download their dendrobium culture sheet. Give it a read and let us know if you have any questions about its culture.

[vcuchick]

My opinion would be to try watering twice per week in the summer months. Since you're south/west window will get stronger sunlight, the plant will stress more. perhaps slowing adding more water or trying s/h might work. But then, I would see what the more experienced Den growers would say...

[11Orchid126]

You should us everything but the pot it was in. What size pot? What medium? Does the pot have drainage holes? This information would be most helpful.

[willowbanks]

I agree with Digitalgate, lack of good light has stoped the leaves at the top from opening properly.

These Dens are not deciduous.

The yellowing leaf at the top of a new cane looks like a fungal attack and normally only strikes during cool weather.

It might be an idea to take a close look at the top centre leaf on the new cane, looks like it is stuck closed, you may have to split this leaf to help it open. (just follow the leaf pattern of the existing leaves and that will show you where to split the centre leaf if it needs to be done)

Bill

[nidiasophia]

Originally Posted by 11Orchid126

You should us everything but the pot it was in. What size pot? What medium? Does the pot have drainage holes? This information would be most helpful.

The pot, I estimate, is a 3-4 inch pot. It is potted in coconut husk and growing new roots. The pot has drainage holes and the medium never really gets too soggy.

[robb]

could yellowing of leaves (and subsequently falling off at a touch) be caused by a sudden increase in light? reading my orchid books, the charts show for dendrobium (i believe mine is a nobile type) a similiar light range as cymbidium. makes sense, since their leaves are similiar shaped. so i moved my dendrobium to the same spot as the cymbidium (filtered direct sunlight) instead of shaded south window (never direct sunlight, but right on the shadow edge) and a week later i find the largest leaves brown and dead. this plant has previously survived with me for over a year, so i must be treating it somewhat nicely. only other big change has been with springtime here, i am increasing it's watering, possibly too much, and allowing it to dry out between waterings since i have been away all week at school. any suggestions or ideas appreciated.

[plucker]

Originally Posted by kmarch

nidiasophia, I dont' think your dendrobium is the species Den biggibum. It looks more like a biggibum hybrid, aka a phal-type hybrid.

I tend to agree with this comment as the canes seem a wee too thick and the leaves just dont look like the ones I have seen in the wild.

If however it is one or has its parentage, then the leaves are kind of deciduous. This plant will normally drop most of it's leaves in the cooler months from the bottom one up. However it probably wont lose every leaf on the plant. They normally keep leaves on the newer canes but they could look sick by the end of winter.

I would have thought that this time of the year for you leading into summer, you would see a plant of this type in the growing phase and not losing leaves, instead growing new canes.

In your case,the leaves up near the top are going. My guess is a fungus. Control now or you will lose a potential flowering cane.

[nidiasophia]

Originally Posted by plucker

I tend to agree with this comment as the canes seem a wee too thick and the leaves just dont look like the ones I have seen in the wild.

If however it is one or has its parentage, then the leaves are kind of deciduous. This plant will normally drop most of it's leaves in the cooler months from the bottom one up. However it probably wont lose every leaf on the plant. They normally keep leaves on the newer canes but they could look sick by the end of winter.

I would have thought that this time of the year for you leading into summer, you would see a plant of this type in the growing phase and not losing leaves, instead growing new canes.

In your case,the leaves up near the top are going. My guess is a fungus. Control now or you will lose a potential flowering cane.

Any tips on how to control? I have some Physan is this ok? How often should I spray it?

[plucker]

I have never used Physan, as it is hard to come by in my country, but I believe it has fungacidal properties and would be worth a try. Just like any fungacides available.

As to how often, well that is a difficult one.
Most growers dont like using unless they have to because fungus could build up immunity if used more than necessary.