potting medium for oncidium

[Angry Professor]

I have two grocery store Oncidiums. (Both look roughly like the 'Sherry Baby' variety, though neither has the right scent.) Both came in a potting medium not unlike what one would expect with a tropical plant: finely chopped peat or something similar, along with some larger particles for drainage. Both are doing well in that medium.

One of these plants is now very rootbound and nearly overflowing its container with bulbs. Based on the medium I remember having been visible before the plant outgrew the pot, I purchased a bag of terrestrial orchid potting medium for the two divisions I intend to make of this plant. However I now see that that medium isn't specifically recommended for Oncidium, and most of the videos I have seen show people potting this species in bark.

My question: is it okay for me to repot the divisions of my Onc. in a terrestrial orchid medium?

Thanks in advance for your help.

[murph7]

I do not think that could work.

Oncidium Culture Sheet

[NYCorchidman]

No, that is a great mix and it is called ProMix HP (high porosity). Nearly all mass produced Oncidium intergenerics and Dendrobiums you see at a super market or big box store, basically anything other than Phalaenopsis, which usually comes in either straight bark chip or sphagnum moss, come in this Promix.

They have excellent drainage and good water retention, so make sure you do not water too often as doing so might keep the mix too wet all the time and kill off the roots.

When I buy orchids that come in this mix, I tend to leave them in it until newer growths start to walk over the pot.
Then I use my own mix.

Any mix is good for Oncidium, depending on your watering habit and other growing conditions.

[bil]

When I pot something like this, I use a shallow, wide pot, about 8" in diam, an about 3-4 inches deep. It's not the width you worry about, it's the depth. I put three 2" balls of moss equidistant round the rim, put the plant in the centre, and fill with sieeved fine bark. That way you get plenty of air to the roots, and the moss helps keep things damp.
Soil like media would be a very bad idea.

[murph7]

great to know!

[Angry Professor]

The terrestrial orchid mix I have is E.B. Stone Organics Orchid Mix. It looks a heck of a lot like the ProMixHP, with a mix of finely chopped organic material (peat of some kind), big pearlite, and bark chips.

---------- Post added at 04:46 PM ---------- Previous post was at 04:08 PM ----------

Originally Posted by bil

When I pot something like this, I use a shallow, wide pot, about 8" in diam, an about 3-4 inches deep. It's not the width you worry about, it's the depth. I put three 2" balls of moss equidistant round the rim, put the plant in the centre, and fill with sieeved fine bark. That way you get plenty of air to the roots, and the moss helps keep things damp.
Soil like media would be a very bad idea.

I'll take your advice, bil, and go with a wide, shallow pot. Do you dress the top of the potting medium with moss, then?

[Dollythehun]

I'd like to see that bark mix. My oncidiums are thirsty plants but good drainage is a must. I use small bark and sometimes add a string of synthic or some chopped spag. I keep them in clay to keep the roots cool.

[estación seca]

Where you grow will have a huge impact on how you should pot your plants. Oncidiums are very thirsty plants, but they don't like waterlogged roots. People with plenty of time on their hands, who can water every day if needed, do well with bark. Others find more water-retentive media are better. I would not recommend an orchid neophyte grow an oncidium in bark unless there is time to look at the plant, and water if needed, every day. The sort of medium your plant came in works very well for many people if they are careful not to keep the plant wet.

If you grow in a high-humidity environment, you can use a pot/medium combination that dries out faster. If you grow in a low-humidity environment, use something a little more moisture retentive.

[bil]

Originally Posted by Angry Professor

I'll take your advice, bil, and go with a wide, shallow pot. Do you dress the top of the potting medium with moss, then?

No, as Dolly said, "My oncidiums are thirsty plants but good drainage is a must."

You are trying to balance keeping it wet, with keeping the medium open.
I don't know if dressing the top does much, one way or the other, but I worry it might reduce airflow to the roots. So mine just has bark on the top. I do recommend sieving it so that all the fine pieces of bark are removed to as to keep the bark nice ad open.

If you use the skewer method, remember it will give different results if it passes thru a ball of moss or not.

[nogreenthumbs]

What a great thread, since I have a new to me Gilded Tower Mystic Maze that will need to be repotted soon. I was wondering if it liked more moisture since it seems to be in something that stays pretty moist. The top is smooth and covered in moss and the bottom holes stay moist for a while. I feel like it may be a bit too moist, but I'm heading to a local orchid shop this weekend and hope that I can find some good media there.

This plant will probably indoors in AC 24x7 365. I may in the fall experiment with a north facing or possibly east facing window box, but who knows. For now the plan is 100% indoors in AC. The AC dries things out pretty quickly, so it sounds like some bark with some sphagnum moss mixed in might be a decent solution? What do you guys say?

Thanks in advance. I'm very much a novice at this stuff, so I'm trying to read as much as I can. I've got a Cattleya Chyong Guu Swan 'Ruby Lip' that I got back in Oct/Nov that's still alive and a month old NoID Phal that looks like a I-Hsin 'Sesame', and then I've got the Oncidium that I've had about a week.