Newb Oncidium Potting Medium Question

[Devogenes]

Hello orchid wizards.

I am a brand new orchid parent. I recently took in two phals, and so far so good.

Today the local grocery store had a sale on their Matsui orchids. I figure this is because they've been on the shelves for a while and they want to move them, so I stepped in to adopt an oncidium.

Unlike the phals which I got (also grown by Matsui) which are growing in bark mulch, this oncidium seems to be growing in a sort of peaty-moss medium. Which is pretty damp.

Should I be worried about transplanting this into something like wood or coconut fiber, or is it safe to wait until after the blooms?

[estación seca]

Welcome to the Orchid Board!

I have some oncidiums bought at Trader Joe's in medium like that. I asked an orchid grower friend in Florida about them, and he said not to worry, wait to repot until they start to grow again. One of them I bought in May, and it was in flower for almost 3 months. It just started growing so I'm going to move it. The other one just finished flowering but hasn't started growing yet.

Don't let them dry out for too long or you'll lose flowers.

[PaphMadMan]

I agree. Just be careful with your watering, and wait until a good time to repot into better long term media.

[Devogenes]

Thanks for the answers.

So is it recommended then to repot after flowering, or to wait until new growth seen?

[estación seca]

For most orchids the shoots grow at the same time as the roots. But there are some that grow shoots first, then later roots. With most orchids, you should wait to repot until roots are growing.

I forgot to add - sometimes, when you get a new orchid and the medium is extremely bad, you have to repot right away, regardless of growth. A good example is the Phalaenopsis sold in wet sphagnum moss, in bags with no drainage. These need to be repotted right away if they are to survive. But you shouldn't let your own plants descend to this condition, and you should choose to repot them at the best time for them.

Orchids sold cheaply in supermarkets and big box stores have usually been repotted some time ago, and the medium is starting to break down and rot. The business plan is to wholesale them in bud, just before they should be repotted, so as not to invest a lot of labor, potting media, bigger pots and greenhouse space to growing them larger. The majority of people throw them away after they bloom.

[MrHappyRotter]

It's potted in promix. Some nurseries grow their orchids in it because it reduces watering needs (saving them time and money). Unfortunately, in household conditions, it tends to a difficult mix to grow in, because it will dry out very quickly on top, while remaining wet inside.

The best time to repot Oncidiums (and really most other sympodial orchids) is when you see a flush of roots starting on the newest growth(s).

So, while I'm a big fan of repotting plants soon after getting them, if it's not a good time (i.e. no new root growth), you're probably better off waiting.

[Devogenes]

Thanks for the reply!

It's difficult for me to tell if there is any new root growth as the plant is in an opaque plastic container... But, it is still in flower. I gather that I should be on the lookout for new growth after the plant is done flowering and has had some rest time? Or could there be new growth at any phase?

Is above-ground growth a fair indicator of root growth?

[estación seca]

Hybrid Oncidiums usually rest after flowering, and sometimes begin growing before the flowers are finished. They usually grow new roots and shoots at the same time.

You may be able to slide the root ball out of the plastic pot and examine the roots.

[Orchid Whisperer]

Originally Posted by Devogenes

Thanks for the reply!

It's difficult for me to tell if there is any new root growth as the plant is in an opaque plastic container... But, it is still in flower. I gather that I should be on the lookout for new growth after the plant is done flowering and has had some rest time? Or could there be new growth at any phase?

Is above-ground growth a fair indicator of root growth?

Unless the plant is potted way too deep, you should see roots at the surface of the pot, growing from the base of the most recent growth/pseudobulb to develop.

When I repot an Oncidium, I use for bark for the new medium, same grade as I would use for Cattleyas.

[Ray]

As a new orchid grower, the choice of potting medium is tougher than it may be for a more experienced grower. The key is to provide sufficient water, without suffocating the roots (THE key to success with all orchids), in a schedule that suits your needs.

Besides your own tendencies (do you like to "mess with" your plants, or are you limited to once-a-week watering, for example) there are actually four variables in that "equation": the moisture-holding capacity of the potting medium, how open and airy it is, how your growing environment affects the rate of evaporation, and how the choice of container also affects that.

As an example, in my warm and very humid greenhouse, I grow oncidiums in sphagnum moss in baskets. The moss holds a lot of water, but I don't pack it extremely tightly, and the airy nature of the basket allows it to dry easily and uniformly, so the roots have lots of air. When they are in bloom, and I bring them indoors (we're enjoying a Sharry Baby in the kitchen at the moment), that much drier environment has me watering the plant every other day. If it was going to stay in that window permanently, I'd use a plastic pot to slow the evaporation rate, and probably use a bark/moss mix to open it up a bit.

In other words, what works for one grower, may-, or may not be good for you, so you need to do some assessment of your conditions and time availability before you decide.