Nobile Dendrobium Canes
 

Hi Everyone!

Think you could help me diagnose this poor guy? It's a nobile dendrobium, Love Memory 'Fizz.' First attempt with nobile. It gave me gorgeous blooms all over last winter. I didn't repot it when the new canes began, I thought since it was in coconut husk, it could go another year. Now I'm rethinking that.

Conditions:
It's been dealing with Texas sun in the morning under a 50% shadecloth. I normally water when it starts to feel lighter when I pick it up, much more frequent here in 100 degree summer weather, 2-3 times a week lately. I didn't have shade cloth until a month ago, the poor thing's been dealing with quite a bit of sun. I just have an apartment balcony, so it gets kitchen sink watering at the base only. I think my water is limestone-y and tests at about 8.5 PH. I haven't noticed any bugs, but I did spray it with some Imidocloprid in late June just to be sure (I'd bought some new orchids and they were quarantined, but in case anything flew everything got sprayed.)

Problems
It seems like the back canes are going yellow - most yellow, then hard and brown, but one (red arrow) is going mushy at the base. And when I looked more closely at the plant I noticed some of the new canes had brown spots where the new flowers would normally come in, and they don't feel mushy yet, but do feel less firm than other flower node areas.

Questions

• Your thoughts?
• For the old canes, if they go yellow, should I just cut them out, or are they still useful nutrient storage?
• I thought nobiles would keep their old canes longer, do they just shed those after a couple years?
• Think this could be shedding old canes and I could just ignore it, or should I repot? I'm leery of repotting, don't know if that's going to be the final stress factor - it should be setting up for it's dry season.
• Could it be a problem with the water ph?
• If I cut out canes should I also cut out any new growth cane that has this brown spotting at the flower nodes?

Thanks for any advice you can lend!

Regards,
Kara
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:bump:

Hello Kara,
Your plant looks good to me. and yes the old canes do get yellow as they get used up by the new growth. The nodes look fine to me, and it does seem that you have some rot on the bottom of one of the canes, I would just flush the plant with some hydrogen peroxide to treat any rot.
I would not cut any new growth until I see the brown spot spreading. My Memory fizz is one the plants that seems to get does spots when I water with water straight from the tap.

I only cut the old canes ones they start to dry, let them get yellow and rubbery then cut.

Repot if the medium is deteriorating, if it brakes in your fingers with little pressure then is time to change it. And remember that if you repot, you will need to water more often, because the new medium does not hold as much water as the older medium.

If you cut out canes make sure that you cure the cut with some cinnamon, make sure you don't let any get on the roots.

One thing I have learn with nobiles is that they don't like cold water, they like more room temp water, and early morning watering, any time I have water them after 9am they seem to not have enough time to dry before sun set. So I set the water out the night before I water (and I also use coconut for my plants), my nobiles get direct morning sun until about 11:00, of course the weather here is different then yours.

Now, I only being growing my nobiles for about 4 or 5 years, so I hope some one with more experience can give you some advice.

Thanks LizB88!

It's good to know that's normal behavior for the canes and not to worry. I ended up cutting out the one "mushy" cane, luckily it was still green at the base, and applied cinnamon. I've left all the rest in place.

The media can probably wait until spring for replacement. I had prepped a partial "brick" of coconut husk, and the sponginess/crumbly-ness between the two samples feels similar, but not easily crumbling in my fingers- slightly easier with the stuff in the plant, but not easy. Either way, now I have prepped coconut media I can bag up once it dries out, and just whip out when I'm ready.

Is the brown at the flower nodes typical? I don't see it on all the canes, and don't recall seeing it last year. A little browning at the split point for the leaf sheath, yes, but not the same as what I'm seeing here.

Regards,
Kara

Some browing can happen when water sits between the leaf shit and the cane. I had that happen ones or twice. You can clean it with some rubbing alcohol. I use a q-tip dipped in alcohol and that seems to keep it from spreading. Is only a problem when it spreads. I have not had an issue beyond just getting one or two in a cane.