Dendrobium: fast new growth but old canes wilting/ is it Nobile?

[stefpix]

thanks for all your info...
the garden centers at home depot and lowes here are a little under furnished for tropical stuff... if i put the kingianum in just pumice - how often would you water? 2 inch pot. 80s/70s lately here...

[stefpix]

I checked on the websites of the 2 box stores - no pumice except the one that you can use to scrub yourself!

I have volcanic lava rock. It feels somehow similar to pumice but the color is different. could it be a decent substitute? after all they both seem some sort of lightweight porous stone...

[King_of_orchid_growing:)]

If you just use pumice, just wait till they dry out completely then water again.

I guess lava rock works too. Try it out.

[Stickygreengo]

Hey Stefpix-
Pumice and "lava rock" are both igneous extrusive rocks that have similar characteristics (vesicles, etc) but are differentiated by their chemical composition. The lighter-colored rock is pumice, and is composed of quartz (silica). The "lava rock" is called scoria, and is composed primarily of iron, magnesium, and also silica (commonly what comes out of volcanoes forming on oceanic crust; think Hawai'i). Anyway, I don't know much about orchids yet, but my geologic knowledge tells me that the rock composition is not as important as rock texture as far as mediums go...