Medium for miltoniopsis
 

I bought a rather large miltoniopsis lillian nakamoto in the "discount" section of a garden center a few months ago post-bloom. When I got it home, a bunch of its leaves turned yellow and black and fell off. I treated that as if it was a fungal infection and sprayed it with a fungicide. That seemed to help and after I put it somewhere in my home that is cooler and gets more airflow, it has been doing seemingly fine. Only one leaf has black spots now and I can't tell if it's fungus or just...black spots.

Recently, it has started on two new pseudobulbs! However, it is super big for its pot and there is a huge tangle of dead dried out roots on top so I want to re-pot it. What would be the right medium? And would this be a plant I should consider semi-hydro for? I am in a low humidity house (less than 20) with wintertime daytime highs in the high 60s and nighttime lows in the low 50s. Summer daytime highs in the 80s and nighttime high 60s.

Also, whenever I water it I get a whiff of a pungent, difficult to describe scent. A bit acrid, kinda ozone like? Is this normal or does it indicate something bad going on in the root zone?

Sounds to me like the odor of decaying organic matter. Could be roots and could be the potting medium, or both.

The best time to repot is just as new roots are emerging from the base of the plant, but in this situation, waiting for the next round of new growth might doom the plant, so I’d go for it.

When you change the medium (even if that’s fresh stuff of the same mix), the plant will need to grow new roots, so you’re going to want to “baby” it for a few weeks to let it get reestablished.

Thanks for the advice! All I have on hand right now is some "chunky" phalaenopsis mix from Better Gro and some spaghnum moss (sidebar - I also got a bag of better gro bark at Lowes but it was quite mildewy smelling/musty in the bag - is that OK to use?). Qualitatively the bark I have, especially in the phaelonopsis mix, seems too coarse for how thick the roots look. I suppose I could sort it by hand and find some of the smaller pieces in it. Will that be appropriate for a miltoniopsis? I am also planning to make an order from Kelly's Korner or Quarter Acre for some finer bark or coco husks, but that won't be here for at least week or more. I will say the odor has been around for at least three months already and there are new roots growing currently.

I don't grow miltoniopsis yet but they're the type of orchid I'd like to try growing next so I've been reading up quite a bit on their care.

First off, have you looked at the roots? Hopefully, you should be able to gently work the pot off the rootball/medium without disturbing it too much.

Take a look, take some pictures, and post them here so people that do grow miltoniopsis can help you troubleshoot if you need more help.

Without seeing the plant, if you think you can baby the existing medium situation for a week while you wait on a bark/medium order without letting it stay soggy or too dry, repotting once into the "correct" medium (correct for your conditions and your care habits) would be my choice.

Moving a finer rooted orchid into a different and still unsuitable medium for a week or two isn't going to make the situation much better for the plant and may end up increasing the total amount of stress/root damage/etc. done during the repotting and re-repotting process.

Now, if you pull the plant out of the pot and find a rotting sludge, it may be worth the temporary repot into the less-than-ideal chunky bark just to get the roots out of the broken down bark soup. Look at the roots and make your choice based on what you find.

Good luck!

Here are some pictures of it. Wish I had taken a look earlier, but I didn't want to disturb the roots when I didn't have anywhere new to put it. But wow this is not looking like a happy root situation! Last pic is one of the new growths with new roots coming out.

Pictures:

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PXL-20220203-175037805 — ImgBB

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Shoot, I don't think they look that bad. But sure ready for a bit bigger pot.

I don't grow them because it's too hot here. I had hoped some of our expert Miltoniopsis growers would be here but they aren't.

Fine bark or sphagnum works well with these. If you aren't an expert grower I would not use medium nor large bark. These need a lot of water and should never dry out. If you do put it into medium bark consider standing it in a dish with a small amount of water.

Homes are problematic for them. They like to be cooler than most of us like our homes, and also much more humid. They prefer water low in dissolved solids, like rain or reverse osmosis water. They do need regular fertilizing.

I would take your plant to the sink, rinse off whatever old medium comes off easily, then repot into the sphagnum you have, packing it tightly.

Watering with sphagnum is different than watering with bark. Unless the plant is taking up so much water it drains the sphagnum dry in a few days, you don't want to soak it completely. Just run water over the top for a second or two. The water will diffuse through the moss rendering it moist but still well-aerated. Sphagnum lasts up to two years in a pot, so plants in sphagnum must be repotted often. But a Miltioniopsis grown well will need repotting in about two years.

Thanks for the advice, I'll give the spaghnum a go. I think this is probably the one time my drafty uninsulated "apartment" (converted row house) has ever been to my advantage. Those crappy windows certainly don't help my electric bill but the miltoniopsis does seem to enjoy it there. How worried should I be about overpotting this guy? I was looking through plastic pots I have in the house and what I've got is two sizes up, not just one.

In my experience:

1. Miltoniopsis needs to be repotted every year (they 'hate' stale medium).
2. It is a thin root plant. Depending upon how frequently you want to water, you can choose between two mediums:
2.a Spaghnum/bark mix (3:1, using seedling size bark).
2.b Bark/charcoal/perlite mix (2:1:1, all seedling size)

I do not let the plants get large. I divide into 2-3 PB divisions, and typically squeeze them into a 3" pot. The 2.b mix requires more frequent watering than the 2.a mix.

Wow thanks for the potting mix recipe! Is there a particular cultural reason you don't let them get too large? Or aesthetics. Also, the cultural requirements I'm hearing (cold, moist, always wet) sound like what is often described as the ideal one for semi hydro. Is that a route worth pursuing?