Orchid Culture - Questions & Answers from This Month
by Sue Bottom, from the St. Augustine Orchid Society Newsletter. Email us with any orchid question. If we can't answer it, we'll find someone who can! Send photographs too!
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Problem Spreading to Phalaenopsis
Q. I’ve isolated this phal and treated it with 3-1 Bayer and then later with Physan 20. but it’s already spread to four other phalaenopsis. I don’t know what it is. Nothing rubs off. The underside seems clean. Do you have any ideas?A. That looks like mite damage on the top surface, but the bottom looks clean, so I'm thinking it's not the red spider mites but some of those much smaller mites. If you have a loupe or good magnifier, look for anything crawling. I would be thinking of spraying a miticide on all your phals, pronto, something with abamectin in it like Avid. If you don't have any miticide in your aresenal, get out the isopropyl alcohol and add some vegetable oil and dishwashing soap to it and spray all the surfaces. Then, order some Avid to keep on hand for mites. (Oct-25)
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New Growth Rotting at the Tip
Q. What causes a new growth that starts off healthy to start browning at the tip, and then it gets stunted and eventually starts to slowly rot. I have seen that the most among orchids from the Stanhopea alliance. The growth on this Acineta started off great, a hard bulb with no sign of rot at the base. Now it has stopped growing and the tip is getting darker so I am sure it will wither away slowly.A. I haven't had that problem with Stanhopeas so I'm just guessing, but it looks like rot is setting in. Here's a trick from Keith Davis. Have you seen those little plastic cups like apple sauce comes in? You might try placing one of them over the new growth to prevent water from accumulating until it grows up a bit and hardens off, to see if that protects the tender new growth from rot. (Oct-25)
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Dendrobium Keikis
Q. Many of my dendrobiums did not get enough water last winter and did not bloom. The ones that bloomed don’t have many keikis. I have a variety of stressed dendrobiums that now have many keikis.
I took the keikis off when they had three leaves with three roots and planted them in precision Orchiata. Many of the keikis have died. Would ProMix or sphagnum moss have been better? Instead of removing the keikis from the stem, would it be better to cut the stem in sections for each keiki?
A. The Orchiata would probably have worked if it had been watered every day or every other day until the roots grew into the mix.
During the summer, the soft cane dendrobiums seem to really like monsoonal conditions before gradually reducing the water as we move into fall. Had you planted the keikis in sphag moss, it would have been more forgiving and not required that frequency of watering.
I usually twist off the keikis if the cane is still plump, but if the cane is starting to dessicate, you can remove the cane and plant it with the keiki and the cane will help sustain the keiki until it becomes established.
Here's a summary of cultural tips for different types of dendrobiums.
(Oct-25)