Miltonidium Potting Medium

[JenHowlett]

While on "vacation" this weekend, I purchased a Mtdm Rosey Sunset 'Pacific Satin' at Home Depot. I couldn't believe it, but its a huge plant (its bursting out of its 6" pot), has two spent spikes, four more still full of blossoms, and a dozen new growths (I can't believe the kind of great shape its in!).

Anyways, I know that I'm going to have to repot it. I've done a little internet research, but there seems to be inconsistencies in the recommended information. Its currently potted in straight (and very compacted) sphagnum.

First, should I repot now, or wait until its done flowering?

Second, what should I repot with? Sphagnum again, or the same bark mix I use for my phals? Should I mix the two? One website recommended using a paph (more normal kind of soil) mix.

Any other information you can give would be appreciated. I'll get photos posted as soon as I can.

[Zoi2]

For my I'd say if it is healthy wait to repot untill after it finishes blooming. You are aware of the compacted sphag so watch the watering so it doesn't get water logged. When you repot use a medium you are comfortable with that works in your growing environment. The plant sounds very nice, can't wait to see pictures
Joann

[WhiteRabbit]

I would suggest smaller bark than for Phals - that is if you can find it. Shouldn't be "soil like" tho. That being said I have potted some fine rooted Oncidium alliance plants in the mix I use for cyms and paphs which is pretty fine bark (too fine on it's own) but mixed with medium bark, perlite, charcoal. Or sphag could be added to medium bark. Just remember sphag decompses quickly, and annual repotting is a good idea when sphag is used.
I usually use either fine coconut husk chips with added perlite, or Gubler's fine orchid mix for fine rooted orchids.

That being said - they may do fine in the chunkier bark mix for phals, I haven't tried that.

Some people grow almost all their orchids in straight sphag, but for others it's an instant recipe for death lol.

Watch your watering in the sphag. Maybe pull out some of the sphag and loosen the remaining. And if you can use a skewer in the pot to determine when to water.

[Ray]

1) As was stated, if you can, wait to repot. Doing so now will stress the plant and shorten the life of the blossoms.

2) When choosing a potting medium, you need to consider the needs of the plant, the growing conditions you routinely provide, and your own watering habits/tendencies/preferences.

Courtesy of a taxonomic shift, the plant is currently named Oncidium Rosy Sunset (note there's no "e" on Rosy) as it is a cross of Oncidium Pupukea Sunset and Oncidium ornithorhynchum. The plant will prefer a fairly constant moisture supply, but plenty of air flow to the root system.

In a home environment, I'd suspect that sphagnum would be too restrictive of air flow, especially right after watering and as the moss gets compact with time. The same would likely be true of a paph mix, unless you are an extremely spare waterer.