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  • 4 Post By EMos
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  • 1 Post By Chris in Hamilton

Is this what rotting Den phal roots look like? #panic

This is a discussion on Is this what rotting Den phal roots look like? #panic within the Dendrobium Information forums, part of the Frequently Asked Questions category; Hi all - I have a few really basic questions about the status of the ...

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  1. #1
    ddennism's Avatar
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    Default Is this what rotting Den phal roots look like? #panic

    Hi all -

    I have a few really basic questions about the status of the phal-type Dendrobium on my front porch, and I hope you'll be kind enough to indulge me:

    1. The tall, slightly swollen vertical structures with 2-ranked leaves emerging - are these "canes"? I've read about hard and soft canes. Which do I have? Does a new one appear every year? If so, it looks like they're getting much smaller every year in my care. Some of the oldest are dropping / have dropped leaves, but I noticed that a blooming stalk is emerging from one even though it had no leaves anymore. When, if ever, are you supposed to remove an old cane?

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    2. Are my roots rotting? I've tried to supply this guy with an aerated, loose soil mix (see below). Some (most?) certainly look dead. I'm so new that I don't have a good idea of what 'normal' or 'healthy' looks like. Newly emerging roots:


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    Older (dead?) roots:

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    3. Is this really loose mix appropriate? It's composed of "ODLA" clay pellets from a popular Scandanavian furniture store and fir bark from a pet store, with a little bit of osmocote slow-release fertilizer. I'm worried that I'll water too infrequently one week and the whole thing will shrivel up. I've been watering about every other day (soaking thoroughly, water running out the bottom) to every three days.

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    4. Help?

    Much thanks in advance -

  2. #2
    EMos's Avatar
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    Hi Daniel, thanks for posting with some very clear pictures. I'll answer a few basic questions and I hope someone with more experience in dendrobium culture can give you more advise on its care.
    Firstly it is a hard-cane dendrobium, it grows a bit warmer and more humid than the soft-cane dendrobiums. And indeed the swollen vertical 'stems' with pairs of leaves growing on either sides are called 'canes'.
    There seems to be a lot of rotten roots on the old canes, but the good news is that there are some very healthy roots emerging from the new growths.
    I believe that you have been overwatering it, and the mix it came from seems to hold a lot of moisture. I suggest you trim some of the old decayed roots, and pot the orchid in a medium grade orchid mix in a small pot and keep it on the dry side with just some occasional misting to encourage further root development. The size of the pot should be just big enough to hold the roots and have a distance of one inch from the newest canes to the edge of the pot (Dendrobiums like most orchids do not like to be over-potted). You might need a stake to hold the plant in place as the canes should not be buried, the base of the cane should sit just above the orchid mixture in the pot.
    How much light does it get?

  3. #3
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    Thanks for your helpful reply!

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    Care history:
    Purchased 3 years ago -------------------, was in-bloom and potted in sphagnum in a green plastic pot with many vertical slits and drainage holes, itself nested in a non-draining clay pot. I never let it sit in water between the nested pots. It occupied a dappled-shaded SE windowsill until blooming ceased. Repotted in 1/3 granite grit, 1/3 seived turface MVP, 1/3 fir bark "medium", + some slow-release fertilizer. 1.5 years spent like this under fluorescent lights in a basement (about 3850 lux*; 10 cm from lights, 12 h day cycle), 55-65 degrees F, more or less constant.

    Current conditions:
    It never really seemed to thrive like this; this spring I moved it to my covered porch where it is about a meter from the NE-facing ledge (pictured). It is nestled between other plants, experiencing dappled morning sun (about 16500 lux, except where dappled: 2100 lux). When I moved it I read more about these orchids and was disappointed in the lack of healthy roots. I repotted it in the mix shown above. I don't think I can pot it in a less moisture-retentive mix than that and not have to water more than once per day. As it stands, the topmost clay chunks already generally change color to "dry" after 1-2 days; I water about every 2-3 days.

    I do not have access to a terrarium, greenhouse, automated mister, or RO-water setup. Since spring I've been using the MSU for-tap-water (contains EDTA) fertilizer mix, every two weeks. For all my houseplants, I prefer to use as fast-draining and aerated mixes as I can. I'd always rather modulate water availability by the nature of the mix rather than the frequency or volume of the watering (which, as I've gotten to know myself better, is either daily - every couple of days out of habit, or never, always lifting pots to get a feeling of weight before watering).

    It's hard for me to understand how a few hand-held sprayer squirts in the morning will help much - won't that small amount of water dry about 1 h later? If this guy actually needs regular misting, then I guess I'll have to throw up my hands and give up. I can't afford something like that right now.

    *as measured with my crappy phone lumenometer app.

  4. #4
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    I would agree with Eric, it looks like a healthy plant with some old roots that you can remove with a sterile cutting tool, I would then spray it with rubbing alcohol where you cut the roots and maybe add a little cinnamon to the cut tips. Some cane dendrobiums will spike on a old cane so never remove the old cane unless it starts to get soft at the base.

  5. #5
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    Hi Daniel, misting is only a temporary measure until the new roots establish themselves, you only need to do it every second day or third day. You can if you want sit the pot on a tray of pebbles with water to increase the humidity around the orchid.

    Watering or keeping the plant wet on the other hand will not help the plant at this stage as most of the roots are decayed and they will not absorb any moisture; it will just make the situation worse. Keeping your orchid on the dry side and increasing the surrounding humidity is just one way of encouraging root development.

    With regards to light, dendrobiums need high light levels during the growing period, which I think you have; but they can be kept in a shadier spot while the roots are establishing themselves.

    Don’t panic your orchid can still be rescued

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    Facing same problems...

  7. #7
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    Many thanks for the replies, EMos and JDT. I cut the roots to the extent that I could, leaving mostly only the white to white-green young roots pictured above. It is very strange to me to be left with an essentially rootless plant after all this. What do healthy adult roots look like when they're growing in a loose mix like this? Are they still white/white-green like the ones I see growing out of grocery store Phalaenopsis containers? Is a color change a sign of maturity? Death? Right now I just don't know what success will look like!

    I also have a question about assessing water content of such a loose mix. I'm familiar with growing houseplants in loam-mimicking peat-heavy mixes where you can easily assess water status by weighing the pot before and after saturating it. This loose mix is much less water retentive, and it doesn't seem to change much weight-wise before and after saturation.

    Thanks for putting up with me -
    Daniel

  8. #8
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    You gave a great summary of your culture and conditions but one thing I can't see is the type of pot its in now. Plastic within clay can fool you. The surface is dry but if you pull the plastic pot out you will probably find lots of condensation on the outside of that meaning the mix is still moist. This time of year that should be okay. Dendrobium's do not like to dry out completely when growing. Beginning around early October you should start to let the mix dry before you water again. Over watering during the winter months is probably what caused your root loss. I made an error this past winter exactly this way. I had several large Den's in plastic pots last summer but placed those pots in clay ones to prevent their blowing over. Forgot I had done that and thought that I had repotted into clay. We had a very overcast fall and early winter so they never dried. Anyway, learned the value of keeping records. I wouldn't change the mix you are using. It drains well and watering every 2-3 days in growth cycle is where you want to be. Also when ever you change the medium with orchids or any plant for that matter you will lose new root growth as it comes in contact with that medium. The plant will then have to work at growing new roots. Also, it is quite normal for Dendrobiums to lose some of their roots when dormant just not quite as many as you've pictured.
    Last edited by Chris in Hamilton; July 14th, 2016 at 06:46 AM. Reason: Another thought

  9. #9
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    Healthy roots on an orchid even when well established are almost white, and will turn slightly grey/green when watered.

    Picture below is one of my cattleya growing in a loose mix before re-potting.

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    There are a few ways to check moisture levels in an orchid mix, if the weigh method doesn't work for you, you can rely on observation, see how the the mix changes colour when it is watered, and when it is dry, but you have to be careful, as this only indicates the amount of moisture on the surface; to check the humidity inside the pot you need to use a pencil or a wooden skewer; the point of a pencil or skewer when inserted into the medium will darken if the medium is still wet.

    And lastly as Chris pointed out, the type of pot is also important, there should be enough air circulating through the roots, as orchid roots like to breathe and slightly dry out between each waterings.

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