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While returning from a camping trip over the weekend, I picked up a bag full of Eucalyptus tree bark. The species, I believe, was robusta, so the bark was soft, very fibrous, and airy. The University of Hawaii did some experiments years ago to test the bark as a growing medium and found that it was not suitable. I also conducted my own trials with the same results: The roots of Cattleya would stop growth immediately upon touching the bark. Only after several years, did the plants eventually grow roots on the bark.

It occurred to me that in its habitat, nothing grows on the bark. There are no weeds, mosses, or anything else on the trunks of the trees. It seems there is something about the bark that prevents growth. The University did not do research on what trait of the bark prevented growth.

I put the bag of bark in a tub of water in order to leach out anything that might be in it. Unfortunately, the bark floats like a cork and does not soak in any water. Interesting characteristic. I don't think this is what prevents growth on it. I'll find a way to submerge the bark.

In the meantime, has anyone tried using Eucalyptus bark as orchid media? What results, and what "treatment" are needed before use?

One thing I've learned, if the shape could be maintained, this material would be great for life-preservers. Lots of air that doesn't come out unless considerable pressure is applied. Took probably 100 pounds of sash weights in order to submerge the bag.

I suspect it is the eucalyptus oil that is hydrophobic. Waiting for the Aussies to answer your main question... I understood canaliculatum could be found on eucalypts??

I would be very wary of Eucalypt Bark as an orchid growing media because some species of eucalypt poison the soil around them to the point where no vegetation will grow and others will allow vegetation right up to the base of the tree. As an example a friend in the Dandaragan district north of Perth cut out every common blue gum because they poisoned the soil but red gums (then Eucalypt calophylla) were left because grass would grow right up to the base of the tree, Eucalypt calophylla has recently been renamed Corymbia calophylla. I know that some Eucalypt woodchips have been used in orchid media but not heard of bark. some eucalypt barks are used to tan hides because of the high tannin content. Tannins could be harmful to orchids.

Ross, there is considerable research being undertaken to assess the health benefits humans accrue from the consumption of tannins - in particular the anti oxidative effect it provides. Conversely I often hear comments to the effect that "tannins" will have an adverse effect on orchid culture. Now I am aware of the Nitrogen draw down effect, but am curious what evidence exists to support the notion that tannins are harmful. Seems to me one person comes up with the hypothesis, and before you know it, it is folklore. I am somewhat sceptical given the large number of epiphyte orchids.

[quote="sabredance"]Ross, there is considerable research being undertaken to assess the health benefits humans accrue from the consumption of tannins - in particular the anti oxidative effect it provides.

Sabredance....I believe from my Biochemistry 101 that the tannins are similar to those in common black tea. If so, it would explain why years of applying cold tea bags to my eyes at night time on going to bed has left me a 65 year old virgin with no facial wrinkles.

Does anyone else think that Nigel is using this site to seek a date?

[quoteIf so, it would explain why years of applying cold tea bags to my eyes at night time on going to bed has left me a 65 year old virgin with no facial wrinkles.][/quote]

Maybe adding some wrinkles might help with your other "problem".

Albert

Cym suave and canalicultaum both grow on Eucalyptus trees here but have not seen madidum growing on Eucalyptus as yet - usually on rainforest species of trees.

I only use some very old composted eucalyptus sawdust as part of growing media for both canaliculatum and suave very successfully. NZ pine bark for madidum.

Other native dendrobium orchids grow on eucalyptus trees as well around here.

Gary..

Gary S wrote:Albert

Cym suave and canalicultaum both grow on Eucalyptus trees here but have not seen madidum growing on Eucalyptus as yet - usually on rainforest species of trees.

I only use some very old composted eucalyptus sawdust as part of growing media for both canaliculatum and suave very successfully. NZ pine bark for madidum.

Other native dendrobium orchids grow on eucalyptus trees as well around here.

Gary..

Gary, is the species robusta? Seems that's the one that nothing grows on.