Yellowing Canes on Dendrobium

[Mercurius]

Just noticed this earlier. One whole cane is yellowing a bit and some of the other leaves are slightly discoloured. The lower leaves on that discoloured cane are starting to get slightly wrinkly, too. This one sits I the kitchen counter and gets evening sun from a west window. It gets soaked weekly with dilute fertiliser. I keep two containers of water there to help with local humidity.

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That's a very large pot for that plant, and the medium looks quite water-retentive. I am concerned the roots might be rotten. That is a cause of yellowing on a healthy youngish Dendrobium phalaenopsis hybrid.

This kind of Den. needs to be kept on the dryish side during cooler weather, until it begins growing again, and forms new roots. Watering Den. phals plentifully through the winter risks rotting. It is best if they dry completely in a few days after watering in the winter, and are not watered again until after spending a day or three dry. They're dormant and not using much water.

I would take it out of the pot and be sure the roots are OK. Then repot into a much smaller pot, barely big enough to accommodate one future growth. A very large-chunk bark is better for this kind of warmth-loving Den.

[Mercurius]

Thanks! I'll be sure to get some coarser bark and put it in a smaller pot. The pot it came in was about that size which is why I put it in that one. It actually had a new cane starting, but about a month ago it got soft and I had to cut it off...you can still see the little bit that's left covered in cinnamon..

And sorry the pictures are sideways..my phone was acting up and the site didn't wanna let me upload. x.x;

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That information suggests it is likely to be a too-wet problem.

[Mercurius]

Would something like the All Purpose Monterrey Bark Imperial Orchid Mix from RepotMe work for both this one and my oncidium? It's small and medium pine bark with medium sponge rock and granite chips.

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People differ in what they use for these, but for a Den phal I would use only large chunks of something. Nothing medium, nothing small. I don't understand why people mix bark, pumice, rocks, etc. rather than just bark. I want to do anything possible to avoid medium staying wet too long during cool weather, as often happens with small and medium chunks.

[Mercurius]

And for the oncidium? Would the same coarse bark work? And does it matter if it's bark or coconut husk? Also, I'm curious how you can tell so easily that it's a Den phal and not just a den.

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People often put Oncidiums into finer media, or even sphagnum moss, because they use a lot more water than many other orchids. Some use coarse bark successfully. I can't do that in my warm, lower-humidity climate. It will depend on how warm and humid it is where you grow. In large bark most people will need to water oncidiums almost daily.
I am an outlier on the other end of the scale. I need to stand some of my oncidiums, growing in sphagnum moss, in dishes of water for them not to pleat while growing. Not many people can do this without rotting the plants.

Coconut husk chips (sometimes abbreviated CHC) retain a lot more water than bark. I personally would not use CHC for orchids that ever need to dry out. I have not used them, but I suspect they would be useful for slippers and cloud-forest orchids that shouldn't dry out. Other people have great success with CHC and lots of different orchids.

People sometimes aim to have just one potting medium; in this case, they will need to water their plants on different schedules. If I used only one medium it would be coarse bark. Other people use different media for different plants in an attempt to get everything watered on the same schedule.

Before Dendrobium antennatum hybrids began appearing in the US trade, Dens with long pseudobulbs were either Den phal hybrids or Den nobile hybrids.

Dendrobium phalaenopsis hybrids have a characteristic look to them. They grow stiffly upright and may get over 6 feet / 2 meters tall for some hybrids. Their pseudobulbs / canes are thicker than plants descended from Dendrobium nobile and related species, whose pseudobulbs tend to be thinner. Nobiles usually dangle as they grow (unless staked upright, which I find is difficult to do.)

Den phals tend to have much thicker individual roots than Den nobiles.

Den phals have fairly short, thick, stiff leaves that tend to arch, then turn down a little at the tip, but not droop down; they are often dull rather than shiny, but may be shiny. D. nobile hybrids tend to have longer, very thin leaves that often droop down, and are almost always shiny.

Den phals should keep leaves for several years if grown well. Den nobile hybrids often lose all their leaves each year, or keep them only two years.

Your plant is stiffly upright with thicker canes. The leaves are longer and thinner than most Den phal hybrids, however. It might have some Den. antennatum related species in its background.

Den phals need to be warm in the winter, but with somewhat less water. Den nobiles need a much cooler winter; many people don't water them for 1-3 months or more in midwinter.

[Mercurius]

Wow, that's a lot of information. Thanks for the explanation. ;o I'm still pretty new to orchid growing (as I'm sure you can tell) so I'm still getting used to different types of media and what works best for each species.

Most of what I have are phals that I've been given or rescued from a garden centre; a few were just losing their last blooms and were on red tag clearance on death row. I have one of my larger phals in a mostly CHC medium and it seems to be quite happy. Each of its two spent flower spikes has a keiki, though they've yet to start rooting.

Now that you mention pleating, my oncidium does have quite a bit of pleating on its newer growths and I was really wondering what caused that.

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Once you learn which end of the cookie to bite, you can use the Search and Advanced Search functions in the top maroon menu to read scads of older threads here covering SO many different kinds of orchids. It's what I do when I'm thinking of buying something I'm not familiar with, and it's kept me from buying lots of things that probably don't stand a chance here.