Two Oncidium issues: Black stripe on one, new growth dying on other

[kdennis14]

Hello,
I am really interested in trying to grow in red lava rock. Is that all you use? Can all orchids grow in it?
Thank you,
Karen

[My Green Pets]

Originally Posted by kdennis14

Hello,
I am really interested in trying to grow in red lava rock. Is that all you use? Can all orchids grow in it?
Thank you,
Karen

I buy bags of red lava rock at Home Depot, price is less than $4. Once home, I dump out all the rocks and spend some time to sort them into large, medium, and small pieces. I put them in mesh baskets or buckets and rinse them thoroughly to get the red dust off of them (do it outside, don't let that red sandy stuff go down your drain!)

I use the largest pieces for Vandas, the medium-sized pieces for Cattleyas, and the smallest for Oncidiums. I grow my Bulbophyllums in lava rock with a layer of sphagnum on top. I'm sure other orchids such as Phalaenopsis do well in lava rock, too, but I haven't tried it out yet.

The lava rock will tend to collect minerals as water evaporates, so it is important to flush it (pour large amounts of water through it) regularly to wash them out.

As far as negatives go, as mentioned it is tough stuff to work with and can cut you. It can also be heavy and could scratch or even break ceramic or glass pots. You have to be more conscientious about fertilizing as the rock will provide no nutrients.

Otherwise it is clean, retains moisture, is attractive, and in my experience orchid roots like to explore all the nooks and crannies. Here is an example of a Cattleya seedling which is very happy in red lava rock. Its roots grew straight through to the bottom of the pot in just a few weeks!





If you do end up trying out some plants in lava rock, please come back to report your findings! Good luck

[kdennis14]

CambriaWhat,
I am busy taking down Christmas decorations for the next couple of days. I did go out and buy a bag of Red Lava Rock, so I am going to try this method. I like everything I read about it. I have a Dendrobium Aggre..... I want to repot this into a slatted wooden container, and use lava rock on this one too. I have been told not to repot in winter. So I will wait.
Thank you so much for your reply,
Karen

[Jade]

Black spots on the leaves aren't a good sign. Usually it's black rot, so you did right, because the first thing to do is to cut and remove all the back parts.
I truly suggest you to save this link from AOS: https://www.aos.org/Default.aspx?id=117
at the left side of the page there is a list of the common diseases that we can find, sooner or later, on our orchids. It could be useful.

Jade.

[My Green Pets]

Update on the first oncidium, the one with the black stripe: I did a virus test today and it turns out it is infected with Cymbidium Mosaic Virus (CymMV).

Photos:

Tested several plants today, this one was the only one infected, you can see the last strip on the right showing the positive result.


Here are some leaf details of the CymMV infected plant. Not only are the leaves spotted and streaked with black, the entire plant has a patchiness to its color. It is not a smooth, flat green.

[NYCorchidman]

Main reason why I stay away from orchids with "ugly" leaves.
Almost always the case.
"If in doubt, toss out" is my policy. hahaha

[My Green Pets]

Yeah you were right from the beginning NYC! Good call!

[NYCorchidman]

Soooo what did you do with that plant??

[LovePhals]

Yes what did you do with the plant? Did you purchase the Agdia strips? I have been curious about trying those as well. I'm glad it was just one plant.

[My Green Pets]

I threw away the little division I had made. I figured what was the point? But I have kept the large plant. Just can't throw it away quite yet. It probably won't be long though, it's starting to go downhill pretty quickly.

Yes, I bought 5 Agdia strips for about $50. Now I wish I had bought 25 for $140, and I probably will before long. I have proposed an order of strips to my local society and hopefully we will have a group testing demonstration at our February meeting. This kind of thing is fun, even if you may not like the results.