Hello. I accidentally posted this question in the archives section and have since read the forum re-organization post. Sorry! I have a small oncidium I bought last week that's in a 3" pot. The tag says it is Onc. Tsiku Marguerite. It is blooming a lot right now, so I know I should wait to re-pot it until it's done flowering. However, when I was watering it I noticed that the pot appears to be 90% roots. I've never had an oncidium before (only a few phalenopsis that I picked up at Ikea over the years) so I don't know much about them personally. I've read a lot of websites and forums and they seem to say that the plant can handle being fairly rootbound. How do I know if it is time to re-pot? On one side of the roots are pressed right up against the plastic, whereas the other side has maybe a 1/2 inch by 3 inch section of sphagnum moss that doesn't seem to have too many roots. Also, some of the blossoms are falling off, and some of the leaves have turned yellow-brown at the tips. Do you think it's just a bit stressed from moving to a new environment? Summer in Philadelphia is very humid, and a fan is on at least 10 hours a day in that room. I make sure that all my orchids are out of the path of the air conditioned blast when I turn on the A/C, but that's generally only for 20 minutes or so at a time, maybe three times an evening. So I think it's generally quite humid and a fairly constant temperature. The oncidium is in a room with two big south-facing windows, about 10 ft from the windows. It gets a lot of indirect light - do you think I need to move it to a windowsill? It's on top of a bookcase where I put any/all of my plants when they bloom, as it makes it the focus of the room. Past plants (including several phalenopsis) have been fine there for a month or two while they bloom. Any thoughts, ideas or suggestions would be much appreciated! Thanks!
It is probably just stressed right now. For long-term care, you should give it more light than a Phalaenopsis. It can handle a south exposure, and I would move it a little closer to the windows that you mentioned. Placing it where you have it while it is blooming is not a problem though. Just make sure when it is done blooming, you move it to higher light. As for repotting, it looks like it is getting close, but not necessary right now. Having said that, since you just bought it, I would re-pot it, since you don't know when it was last re-potted, and some of the moss in the centre may be decaying. Wait until it has finished blooming, and until you can see the start of new roots. Gently tease all of the moss from the roots, being careful not to break any roots. Given that you can't see roots on the one side, it might just be that it is lop-sided, and you won't need a bigger pot. Take a look when all the moss is off, and see if the roots fit nicely into the original pot. If you have to cram them in, use a slightly bigger pot, but not much. Maybe a 3 1/2". Check to see where the new growths are starting from - are they all on one side, or all around? If they are all on one side, place the plant so the back is against the edge of the pot, so you give maximum space for the growths on the other side to mature. You can use moss again, but unlike Phalaenopsis, Oncidiums have pseudobulbs, so they like to dry out between waterings. Moss holds a lot of moisture, so you have to be careful about not keeping it too wet. A better mix is a fine or medium bark mix with perlite or sponge rock and a bit of moss. This mix will keep the roots a bit moist but now wet, and will allow the water to drain quickly. The plant you have is one with roots that are fairly thin compared to others, so don't use too large pieces of bark. I hope that helps a bit. For more info, try the American Orchid Society:http://www.aos.org/AM/Template.cfm?Section=Oncidium&Template=/CM/HTMLDisplay.cfm&ContentID=6852
Hello. Thanks for the response - you gave me a lot of information! As soon as my plant is done blooming I'll move it to the windowsill, but as it has a lot of spikes now it might be a bit. I just like to put blooming plants on the bookcase as it's a focal point in my room. I don't think that there's much moss in the pot over all, as I don't see any except the patch on one side. The rest of the roots seem to be growing around small bark bits. However, when it is done blooming and I investigate re-potting it I'll be able to check it out more closely. Right now it seems like the same volume of water that I pour in the top immediately comes out the bottom. Is it an OK practice to soak it for a few minutes and then let it drain completely once a week or so? Right now I feel like my watering doesn't do anything but briefly kiss the roots before draining out. As I've never had an oncidium before, how will I know if roots in the center are dead? Phalenopsis roots are so easy to tell if alive or dead, but these roots are so skinny that I'm not sure how well I'll be able to tell if they get shrunken and skinny like the phalenopsis roots do. Or will they turn brown? I'm an experienced gardener and houseplant owner, but I know almost nothing about orchids! Last questions - will the new roots grow up out of the pot like phalenopsis roots often do, or will I have to peer at the root ball and try to decide if it looks root-ier? Also, can I use bark chips of any kind? We chopped down several trees last fall and have a big pile of wood chips sitting outside for months. As long as I use small enough bits (and sterilize them first!) does it matter if they are pine, sumac, ash, etc? Thanks so much for your help and advice!!
You say the same volume of water flows out of the pot when you water. This is good, but the moss will stay wet. Make sure you check to see how long it takes for the moss the dry out before you water again. If you water before the media has a chance to dry, the roots will rot. It is okay the soak it, but not for a couple of minutes. JUst long enough to get the water through. Doing this once a week should be good, but you need to check to see if the moss is drying out in your conditions. In winter, you will need to water less. Dead roots will be brown, black and mushy. Just cut them off and re-pot. Healthy roots are nice and white, with a different colour tip. The root tips are usually white, but can be red or yellow, depending on the plant. I don't know about bark. Fir bark is the most common, and I would stick to that. Try contacting a local orchid society or botanical garden for more info on growing orchids in your area. You have Philadelphia listed as your location. Try this link: http://www.greaterphilaorchidsociety.org/ or this one: http://www.longwoodgardens.org/
Thanks so much Kevin! I'll try getting in touch with Longwood Gardens - their "Orchid Extravaganza" a few years ago was what prompted me to try buying my first one. Thanks again - I really appreciate your help.
