Repotting Oncidiums

[orchid_fan]

Hello! I have 2 NOID oncidiums which both developed new growth in late March, only to have the growth spurt abruptly stop about a month ago. Since then, neither plants have been growing larger or developing flower spikes. I was looking at the roots yesterday and think it might be time to repot because the roots are growing out of the top of the pots. Both plants are currently grown in the plastic pots with slits along the side and bottom, and roots are poking out through the slots. My questions are:

1) What kind of pot should I use for these plants? Do I have to use the type with the slits or can I use the standard plastic pots with the drainage holes on the side?

2) Do oncidiums prefer fine bark or medium bark?

3) Any idea why the new growth would just stop developing? Am I doing more harm than good if I repot at this stage?

Thanks!

[PAGrower]

Hello! I have 2 NOID oncidiums which both developed new growth in late March, only to have the growth spurt abruptly stop about a month ago.

Have your lighting conditions changed? I ask this because I struggled with the same problem until I figured out that some of the windows in my house get far less light as Spring turns into Summer and my trees leaf out. Unfortunately, it can be impossible to know how many hours of natural light a day an orchid is getting unless you are there all the time to observe.

1) What kind of pot should I use for these plants? Do I have to use the type with the slits or can I use the standard plastic pots with the drainage holes on the side?

This depends on your watering habits. Clay dries out quicker than plastic, so you have to water more often, but some people prefer the look of clay pots. The way I get around this problem is to grow in plastic pots inside of clay cachepots. How many drainage holes/slits to look for in a pot also depends on your watering habits. If you are inclined to overwater, the more holes/slits the better. Lja can tell you the best potting medium to use. Mine seem to be happy in medium bark with styrofoam peanuts on the bottom to facilate drainage and a little sphagnum on top to keep the aerial roots moist, but I'm only growing a few, so I'm far from an oncidium expert.

[orchid_fan]

Thanks PAGrower!

As far as I can tell, the plants are getting the same amount of light they always had. My understanding is that oncidiums need bright light, although not direct sunlight. Is this correct?

Also, I wasn't planning on transplanting the orchids to clay pots. Rather, I was wondering if I should use the pots with the small slits all around, or just the plastic ones with the four drainage holes on the bottom. All 4 of my oncidiums came in the pots with the small slits on the side (but from different growers) so I was just wondering if this is the preferred pot for this genus. Thanks!

[PAGrower]

As far as I can tell, the plants are getting the same amount of light they always had. My understanding is that oncidiums need bright light, although not direct sunlight. Is this correct?

Right on the money.

Also, I wasn't planning on transplanting the orchids to clay pots. Rather, I was wondering if I should use the pots with the small slits all around, or just the plastic ones with the four drainage holes on the bottom. All 4 of my oncidiums came in the pots with the small slits on the side (but from different growers) so I was just wondering if this is the preferred pot for this genus. Thanks!

Sorry about including the basic info on clay vs. plastic; you obviously know that already. I'm not aware of the special pots you describe being standard for oncidiums. Mine are in the basic four-hole ones. Is your existing medium breaking down? If not, I would probably refrain from repotting if the plant wasn't growing, but I'm hoping others will chime in because as I say, I'm no authority on oncidiums. Some types of orchids don't seem to mind being repotted, others can be a lot more finicky and I'm not sure where oncidiums fall on the spectrum.

[LJA]

Nancy, PAGrower is absolutely right. The type of pot and medium you use will completely depend on your watering habits. I personally cannot stand those plastic pots with the slits for exactly the reason you descriped: the roots start growing their way out of those darned slits; they get pinched, and trying to unpot the plant without damaging half the root system becomes an absolute nightmare.

Oncidiums are epiphytes--air plants--so, strictly speaking, they don't need to be grown in any kind of medium whatsoever. You could chew up a wad of gum and stick those plants to a brick wall with it: they'd be perfectly happy, as long as you were willing to water their exposed roots two times a day during the summer.

Here, we use a mixture of medium bark, fine bark, medium coconut, spongeRok, and medium / fine charcoal. We find that such a mixture holds enough moisture so that the plants don't need to be watered but every 2-3 days in the summer, and 99% of everything we grow is potted in those plain old green plastic azelea pots with the drainage holes on the bottom. The charcoal and spongeRok (perlite) is in the mix to allow some penetration of air even after the bark starts to decompose and we haven't gotten around to repotting quite in time. Also, the size of pot you choose will affect how wet the medium stays between waterings: the larger the pot, the wetter the medium will remain.

As far as the new growth coming to a stall on both plants, it's quite possible that, as PAGrower mentioned, the seasonal change with the sun higher in the sky has altered the amount of light your plants are getting. You may also have seen the new growths start to develop, gotten excited about it, (we all do!) and begun to overwater to "push them along a little" without even being aware that you've done that. The roots may be a little soggy, and that will often bring new growth spurts in Oncidiinae to a screeching halt.

The best time to repot is just as new growth is developing. It allows the new root system to penetrate into fresh media. So go ahead and repot! You can use straight bark if you'd like, or one of the commercial mixes sold at any gardening center. But whatever you use, just keep an eye on how much water the medium is retaining, and don't water again until the medium in your plants' root zone has dried off some. To tell, poke a Q-tip down in there for a few seconds: if it comes up wet or seriously damp, hold off on the water. For best growth rate and bloom, Oncidiums really need to dry off to bare dampness before you water again.

[orchid_fan]

Thanks so much for both your answers! One last question...do oncidiums prefer to dry out before watering or should I keep ii evenly moist, like a paph? Should I follow the same watering rule for odontoglossums too? (That was 2 questions.)

[LJA]

Nancy, the roots of Oncids need to dry off more than the roots of Paphs. Paphs should be grown damp. Oncids really need to dry off, but not dry out.

Here, we grow our Odontoglossums exactly as we do the Oncidiums: water thoroughly, let the roots dry off, water thoroughly, let the roots dry off, etc. etc.

(And, you're allowed more questions. No reason that has to be the last one... )

[Tmai]

Louis, I know this is an old thread but good info for us newbies. I just received an oncidium bareroot (buy an orchid, get a "we don't know what it is exactly", but it's free!!). Would a clay pot with the same potting medium you spoke of work with 2 -3 day watering schedule? Does pot size matter as with dends?
Tami

[Brutal_Dreamer]

Louis, I know this is an old thread but good info for us newbies. I just received an oncidium bareroot (buy an orchid, get a "we don't know what it is exactly", but it's free!!). Would a clay pot with the same potting medium you spoke of work with 2 -3 day watering schedule? Does pot size matter as with dends?
Tami

Hi Tami,

I am jumping in here for Louis since he probably will not see this thread for a few days. The clay pot should work fine. You do not want the pot too much larger than necessary for the plant as the medium will stay wet longer if there is more of it. A clay pot will pull some of the moisture away from the plants roots where a plastic pot will not hold water and therefore dry out faster. If you plan to water every two days and you think the roots will have time to dry out between treatments, then no problem. You just do not want to over pot the plant and cause root rot from keeping it too wet.

Cheers!
BD

[Diane]

Nor do you want to do what I used to do when I first tried oncs. I would put in a big pot and then they would die of thirst because I was so worried about over watering them..... May the orchid god forgive me!