Yellowing Canes on Dendrobium

[Mercurius]

I've got a fairly good idea what my limits are. I do have a vivarium with a couple orchids in it, but I'd rather stay in range of normal household conditions. I'd love to have some vandas, milts, cats, and fancier dens, but short of building a greenhouse, I know I'd never be able to provide the appropriate conditions for them.

[Leafmite]

The easiest way to grow the Phal-type Dendrobiums is in red lava rock or in the smallest pot of a bark mix possible that fits the roots so that the medium dries quickly. They like plenty of water all year but they also need plenty of air around the roots (which requires fast drying with bark mixes). As many of these really don't really like their roots disturbed, I prefer the red lava rock option so I don't need to change the medium every year. With the red lava rock, though, you need to be careful in the beginning as the rock is rough and the roots are tender so staking or wiring the orchid in place and putting the rocks around the roots very carefully is important.

[Mercurius]

What about hydroton, then? It's porous and leaves plenty of room for aeration, but nice and smooth so it wouldn't damage the roots.

[estación seca]

A lot of people use hydroton, more commonly known here by the generic term LECA. If you search on either term you will find a lot about it. I use LECA balls for the semi-hydroponic (S/H) growing technique, which has its own forum here. You can see all the forums by clicking on Forums in the menu at the left.

And read up on the other plants. You will be surprised by what you can actually grow in a house. The usual limitations are winter low temperatures and light.

[Mercurius]

I actually have a local source for hydroton and I used it for the drainage in the bottom of my viv. Would it be a good substitute for the red lava or does it hold too much moisture?

[Leafmite]

Hydroton works really well as long as you always water from the top. During the summer, my Phal-type Den thrived in it. During the winter, I water by soaking the orchid and the hydroton was moving around too much so I have returned to the red lava rock for most of my orchids.
Eventually, the roots should hold the hydroton in place. I use net/basket-type pots but have used clay pots in the past with success for the Dens (they are heavy, too, so the Den won't fall over when it is laden with spikes).

[Mercurius]

That would've been my next question: net pots v. solids. I use net pots for nearly all my orchids and normally water by soaking, too. I think I'll give the hydroton a shot and see how it goes.

[Mercurius]

So a little update on the den and the onc.. The den has lost several leaves now. A few days ago, I took it out of the medium it was in and put it in some hydroton to dry up a bit. The roots were all dry and dead aside from a few new ones. I had ordered some PrimeAgra hydroton (what I get locally isn't moisture-wicking) that came yesterday and I soaked it overnight. After a nice soak in some fertiliser with a bit of Super Thrive, it moved into its new semi-hydro home. One of its remaining roots had gone soft and had to be removed, so I guess we'll just have to give it some time and see how it does.

The onc, on the other hand...I'm still not sure what was wrong with it. I repotted it into a fine bark mix, but there were no signs of bugs in the medium it was in, though it was showing some definite degradation. The roots were all firm, healthy, and quite plentiful. I got three separate plants out of it, but potted them all together as there should be enough room for some future growth.

[Mercurius]

The den isn't looking so well...it's lost most of its leaves at this point. This evening I noticed a bit of white fuzzy mould around the base of the canes and the tip of a root that was sticking out of the hydroton. I mixed up some Physan20 and lightly misted the fuzzy spots and the rest of the top layer of hydroton. I really don't wanna lose it, but it's not looking too good at this point..

[estación seca]

Unpot it and show us a good photo, please, of the base of the plant. You can normally save this kind of Den if the rot hasn't reached the stems, but only affects the roots. They survive amazing amounts of drought (but they don't look very good.)