Help, I think I confused my Catasetum!
 

I picked up this little Monnierara Millenium Magic 'Witchcraft' at the Honolulu Orchid Society show last October. When it started to get "cold" in November/December I let it dry out well between waterings (watering about once a week), but it showed no sign of wanting to drop its leaves, and a couple weeks ago it started growing a new shoot.

Then, a couple days ago, all three leaves on the main pseudobulb turned yellow, and yesterday they dropped off.

If I stop watering, I assume the new growth will be sad, but if I keep up the watering, I'll rot the roots of the dormant bulb. What should I do? ^^;

Don't water again until new roots are 3-4 inches long at least. (I wait for the second flush of roots, then the first group is likely mature enough) . The size of the growth is not particularly relevant. The old pseudobulb is big and fat and firm. Also, you can go another year before repotting... if you did want to up-pot (but only a little bit) this would be a good time to do it, as new roots are probably just getting started... but no water if you do. According to Fred Clarke, it is much better to delay watering a little more than needed, than to start too soon. Check out Sunset Valley Orchids - Catasetinae culture for a culture guide from one of the world's expert on Catasetinae.

Thank you so much for the advice! I unpotted it to take a look at the roots. The new pseudobulb has roots about an inch long and there are a bunch of roots from the other pseudobulbs.

It was previously potted in (nicer quality than I have!) sphagnum moss, and I did have to dampen it a bit to get it off without root violence. Since I'm not watering until the new growth's roots get longer, should I leave it unpotted to dry off (for a little while, or until the roots are ready)? Or pot it in bark temporarily?

Sorry for the newbie questions! I've read the catasetum culture web pages, but it's hard to match things up with what my actual plant is doing, especially given our lack of really distinct seasons here.

[Edited because I forgot to attach the pics]

Pot it up right NOW. (It really is pretty far long in starting its root growth and would have been even better left but what is done is done) It needs to be settled in its medium before the roots get going and they are already well on their way. Sphagnum is probably best for a small plant - once it is in active growth, it will need to be very moist, and bark is hard to keep wet enough in a small pot. (For a bigger plant small bark is OK because there's much more volume) For future reference, don't worry about getting old medium (either sphaghnum or bark) off the old roots. They are going to die in the next year or so anyway. So the old medium isn't going to hurt anything (and actually, damage to the old roots will also not matter) It's the new ones that are vital.

Do wait until the new growth is spreading out its leaves before resuming watering. So probably another 6 to 8 weeks. But get it back into its home right away. The sphag will be damp, there's no other way to work with it, then just let it dry out.

In one of Fred Clarke's talks, he shows a picture of himself holding a Catasetum, in the wild, It is leafless, and has not had any rain for about 4 months. It has tons of new roots... these plants produce roots in anticipation of rain, before they start the new growth. So the plant will not be unhappy with no water, it will be doing what comes naturally.

Thank you so much for the immediate response! I will pot it up right away in sphagnum. Silly question...how do you tell how long the roots are to start watering again? I'll put it in a translucent pot, but I'm not sure I can really see through the moss enough to know.

[Re-read your post, and I will wait for the leaves to get big!]

Again, thank you!

Not a silly question at all... I ask the same thing. Sometimes you can see them as they emerge. But another clue is to wait for the second flush of roots that will emerge after the first batch is established. You'll see them, and after they burrow into the medium, you can probably assume that everything is well enough along. Do check out this link Sunset Valley Orchids - Catasetinae Culture . It is an excellent general culture document for this group of orchids. Your plant is a complex hybrid that seems to have a shorter dormancy than most of the group that Fred Clarke talks about in his notes, and so it also seems to be more forgiving. But Fred emphasizes that it is much better to wait longer than necessary to begin watering than to water too soon.

Repotted, and now I will ignore it for a couple of months! (I am an under-waterer by nature, so I'm sure sphagnum is the way to go.)

During the summer, keep it damp... in fact, if you have trouble keeping it wet, you can even sit it in a dish of water. Think "monsoon" Or just put it outside-where you live Mother Nature will help to keep it watered.

Heh, Mother Nature will keep it watered outside, but will also blow it away! I just had to move my new Spathoglottis in an 8" ceramic pot to a more sheltered location after it got knocked over by the wind! (Though even indoors today I actually had a recently repotted orchid get blown _out of its pot_.) O.O

Thanks for the suggestion about the dish of water! I'm nervous about terrestrial orchids because I have managed to kill all non-orchid plants and even seriously stress a philodendron due to lack of water. ^^;

There may be some terrestrial species in the alliance, but all of those I'm familiar with are epiphytes. Due to their gluttonous ways while in active growth it just makes sense to treat them as terrestrials. I grow mine in a layered substrate, with sphagnum on top. As new roots form, there's a couple inches of sphagnum for them to establish in, but further down I use a mix of composted cow manure with some sand added, mostly for weight. I also put a good sized stone at the very bottom of the pot for the same reason. When the plants are fully leafed out they can blow over easily! Once the roots get long enough to reach the manure, the plant is ready for about as much water and fertilizer as it can get, and the moist manure provides both. I do still fertilize weekly when I feed my other orchids, but I no longer mix up a separate, stronger batch of fertilizer for the Catasetum like I used to.