Dendrobium - Fungus? Spots, leaves falling off - 7 pics

[admsteiner]

Hey guys,

My dendro (Love Memory Fit) has been losing leaves. They turn yellowish and have black spots on them before falling off. These are on the canes which have not yet flowered.

I should note that my oncidium has been doing just dandy, in a smaller pot. No wilting or discoloration of any leaves.

Thinking it may be the NYC cold, I moved it off the windowsill. Thinking it may be fungus I used a soapy fungicide on the leaves (which doesn't seem to have stopped the problem).

Thinking something was wrong with the roots, I depotted it and took a look at the root system, which has almost filled the pot since I transplanted it in May.

Here are some pictures of the leaves and roots. Note that in one pic there's a bluish/greenish substance on a root, not sure where that came from:

Leaves:

[Sandy4453]

I think 2 things are going on here. Those do look like fungal spots but not that terrible and can be controlled with a good spray. Dend. Nobiles lose their leaves and even on the new growths, the lower leaves will fall this time of year. Are you still watering this? If you are, STOP! Nobiles need a complete rest in winter...no watering, in order to get blooms, usually beginning in late winter. Keep it in a bright lit window (or under lights), totally dry until you begin seeing little nubs on the canes and only then, begin watering again.

I use GardenSafe fungicide on my Dends. and it helps control the spotting. You have to keep it up though, routinely.

The flowers on these are beautiful. Yours is going to look sensational with all these canes.

Best of luck.

[whygreenberg]

Yep, Sandy is right. Your Den is deciduous. It is supposed to lose its leaves this time of year. And along with what Sandy says about stopping the watering, it will actually not hurt for it to get the cooler winter temps now as it rests.

[admsteiner]

Thanks guys, breathing a sigh of relief over here. I'll def. post pictures as (hopefully) blooms start coming in a cpl of months.

--a

[admsteiner]

Hey guys,

Wanted to give you an update.

Despite spraying with Physan 20, leaves had continued yellowing and falling off on my Dendro. So I decided on a slightly different approach:

I diluted Physan 20 in a big bowl. I then took the entire plant and dipped it, leaves first, into the solution. Instead of spraying, I soaked the entire plant.

The yellowing stopped, and two months later, has yet to return. While the old black spots on leaves are still there, they haven't spread. No more leaves had fallen off.

Yesterday I noticed four new canes on the Dendro beginning to pop up. Still no buds. One of the new canes is branching off a cane which itself is a 4" long branch off another cane. Looks pretty cool.

Anyway, thanks again.

--A

[Becky15349]

Personally, I think you probably should have left the plant alone...it was just shedding its leaves. Dends do that. I hate to say it, but do not touch the plant anymore...you'll have to wait for the new canes to flower, since that is where all the plant's energy is going right now. Dends do best if you just leave them alone. I don't believe the old cane will flower now

[admsteiner]

I stopped watering it a couple of months ago.

I was worried that the fungus would get the rest of the plant. Right after I dunked it, it stopped shedding. I guess it could have stopped losing leaves coincidentally at the time I treated it.

As an aside, when I bought the plant (at the NY Botanical Garden orchid show last year), all of the flowering canes had all of their leaves on, from bottom to top.

[Becky15349]

Yeah, i totally hear what you're saying...all I can say is, the plant when you bought it blooming probably came from a greenhouse, where did didn't need to lose leaves in order to produce spikes. In other words, it was in such a great environment that it could support both the leaves AND the spikes...but this is frequently not true with us house growers.

I know the spots are scary on the leaves, but unless you see spots everywhere like crazy, or on the canes of a dend, do not freak out. Its a common occurance of senescence that things start to lose color and fall off.

Your plant probably stopped shedding leaves after you dunked it because it thought it might die....again, this is just my opinion, but this is what I've seen. When a plant goes into hybernation mode, it kinda just "shuts down" and nothing happens...i.e, leaves stop falling off.

You're past the point of bud initiation time now...it was roughly november-early jan 2009 for most people in the northern hemisphere. But, it sounds like you've got 4 new growths coming along, and all 4 of those could bloom...but just let it be, promise me...and it'll be an awesome show-stopping bloomer on 4 canes for sure!!!

BTW, I love the nYBG show. I went the past 2 years. used to live at 101st and 1st in The Aspen building. Now I live in chicago, ugh. Home is nice, but I miss it there in NYC.

~B

[admsteiner]

Good to know, never thought of it that way. Still relatively new to orchids (I plan on picking up another couple this year, just have to figure out which type).

I was definitely watering it through November (though I had slowed down at the end of August).

So don't start watering it now and just let it grow? When would I start watering? May/June time?

[Becky15349]

No no, you can water it now, 1x per week. You've got vegetative growth going on, and anytime a plant is in active growth, you want to give it water. Generally I've noticed that when people say "stop watering in the winter" they don't really mean for you to stop entirely...isn't that funny? They actually mean something like, water 1x a week lightly, which is what I do. It can get very confusing, I apologize LOL. Some people do stop watering entirely perhaps, but maybe they are growing in greenhouses and have higher humidity? I don't know. All I do know is, I'm a windowsill grower, and if I stopped watering entirely in the winter, my orchids would whither up and die. They still get sun, they are still metabolizing and transpiring, so why would I not water them? Maybe I water a little less, bc the water doesn't evaporate as quickly in the winter as it does in the summer, but I still water 1x a week. See what I mean? Sometimes you have to think about the logistics of it, because not everyone has the same conditions. Only you know your conditions best, and over time, you will master them, through trial and error.