QuestionQUESTION: I had a happy dendrobium for four or five years. Last July I went on vacation as it was sending up a new cane and left it with a friend, who watered it once a week as I'd been doing (in her own house, in what sounded like good indirect light conditions). The orchid has been going downhill ever since. The new cane died before getting to mature height, the plant sent out several flower stalks (in desperation?) which partially bloomed before dying, flowers wilted quickly or even before fully opening, leaves on the other canes have been turning yellow and dying, it's growing a new cane now which has strongly variegated white/green leaves (never saw this before). In my own desperation, I repotted it a couple weeks ago; it was very potbound; didn't see any rotten roots. At this rate all the leaves will die in a few months. How can I save it?
ANSWER: The plant should be entering a new growth period as summer approaches so you want to do all you can to support that new growth. Don't worry about the leaves. Repotting should help, as well as the root exam you did. Dendrobiums like to be tightly potted so this should be respected when you repot. It should be tight in its pot. Give it as much light and warmth as possible to try to support the new growth and generate additional new growth. Leaf loss is not unusual in dendrobiums. Clearly the plant is confused. Leaf loss signals a rest period when watering should be reduced whereas new growth is just the opposite. I can't tell you what might have happened in your absence to cause this change, but, given we are coming into a time of the year for new growth, I would support that. Be sure you repotted the plant tightly in its pot as they like to be pot bound. Variegated leaves suggest too little light-- hopefully not a virus. Then return to the methods that have produced your past success with this plant.
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QUESTION: Thanks very much; can't tell you how much I appreciate hearing from someone who knows more than I. But I'm not sure I've described the situation well... it's never had anything I'd call a dormant period; it always sends up a new cane, then a flower stalk from that cane, then starts a new cane again quite shortly afterward. I'm worried about the leaves because it's losing them at a frightening rate; there's definitely something else going on beyond normal occasional loss. It's going to lose them all shortly, from all canes. What worries me is that for the last 8 months it's been back in the environment it was happy in (same light, same watering schedule, same light fertilizing), but it's been going downhill in a way that's completely unlike the previous four or five years.
In its previous pot, it was so potbound that I really had to work hard to get the roots away from the inside of the pot, and probably did some damage in removing it. The new pot gives it an inch or so of space on all sides around the root ball. That sounds from your comments like that may be too big -- but I'm afraid to repot it yet again. Is it better to put it back in its smaller pot with new bark, and risk the stress, or leave it in its newer pot?
Thanks again so much.
ANSWER: You can leave it as repotted but tamp the new potting mix down as hard as you can all the way around inside the pot. A potting stick is often helpful in getting the potting mix compacted about the plant. You want the plant anchored well enough so you can lift the pot off from the ground by pulling up on the canes. If the plant comes out of the pot, or is loose in the pot, when you do this, it is not anchored well enough. There are wires called "rhizome clips" that can go over the top edge of the pot and can help to hold the plant tightly if you can't secure it well enough by pushing hard on the potting mix to compact it about the plant. Most of the problems I have seen with dendrobiums is the result of keeping the plant too wet. This is usually the result of the potting mix breaking down and therefore retaining more water in the mix and allowing less air ro get to the roots. Therefore, a plant that may have been doing well, may start to go downhill as less and less air can get to the roots. Also, a dendrobium in constant growth and/or flowering may be the result of year around watering and/or feeding. Eventually, this lack of rest can wear down the plant just as we wear down without appropriate rest. After a growth period, allow the plant to dry out more to force it into its resting period and a more normal cycle.
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QUESTION: Thanks again; I'll tamp down the bark around it, and keep watering it (I guess) to help the new cane along. How long does a growth period normally last, and how often should it be watered during a rest period?
I checked, and I've had it more like 8 years. Its behavior in the last 8 months (since it spent 3 weeks at my friend's house) has been completely different than in the previous 7 years or so, so I'm still thinking that something happened to it while there, that it still hasn't been able to recover from. A virus is one idea, I guess; any other such non-recoverable possibilities?
Thanks very much; I'm very grateful to you for the discussion.
AnswerI think the viral explanation is unlikely because there would need to be a source for the virus (ie another infected plant whose infection was transferred via an insect vector or reuse of an infected cutting tool on the plant). While leaves can sometimes show symptoms of viral infection, it is not usually a variegated pattern that results. A growth period can last for several months and often is terminated by flowering after which it may rest if watering is reduced. I would cut back on the watering and eliminate the feeding once the canes are mature and no longer growing.
