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Gardening Answers Knowledgebase

Knowledgebase record #57

PAL Question 

I have a couple of Dendrobium orchids, and one other that I don't know the name of. Both the Dendrobium have lost all their leaves, and I'm worried that they will die if they are not repotted soon. There is white fuzzy mold growing in the potting mix (which is just bark) of at least one of them, and I researched a little online and found that it is a common kind of snow white fungus (that may not be the right name) that is common to orchids in general.

I'm worried about root rot, and I'm wondering what I can do to try to revive these two orchids back to blooming. I read that soaking the roots in hydrogen peroxide can often help kill the fungus and then repotting thereafter can possibly revive them. What would you suggest for a repotting mix, and do you have any tips on reviving orchids once that have lost all their leaves?

The roots seem to still be intact, and do not appear to be rotted, as far as I can tell. I'm also wondering about good types of greenhouses/shelters to keep them in, as well as heaters to keep them a little warmer in the house -- they seem to be having a harder time with the 60 degree temperatures that my apartment tends to be. Any advice you could give would be great!


Some Dendrobium are deciduous, so your plants are likely acting exactly as they should. However, now that they've lost their leaves, you should restrict watering them through the winter, watering them only enough to keep them from shriveling, until flower buds form. Then, resume watering again. The species of Dendrobium that are deciduous require night temps of 50-55 degrees F during the winter.

Dendrobium grow well in Osmunda fiber, a potting medium, or bark if they are carefully staked, though they shouldn't be re-potted or divided until new growth starts. Also, Dendrobium with 4 or 5 shoots will grow well in a 4-5 inch pot, so you don't necessarily need to increase the pot size when you do re-pot your plants.

If you cut back on the water you give your Dendrobium through the winter, you shouldn't have to worry about root rot/fungi, especially if you repot them when new growth appears.

The advice above is taken from Home Orchid Growing (by Rebecca T. Northen, 1990, pp. 209-212).

Orchid Growing Basics (by G. Schoser, 1993, pp.40-45) shows some ways you can create a good place for orchids inside your home. For Dendrobium, placing the plants in a window with southern exposure, a grow light that will give them 12 hours of light each day, and humidity (Schoser recommends standing the pots on upsidedown flower pots in a tray of water) seem to be the most important considerations.

The Miller Library has many, many books on orchid growing.

Also, you might want to investigate the Northwest Orchid Society.

Keywords Orchidaceae (Orchid family), Dendrobium
Season All Season
Date 2007-12-13

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