Yellow/burnt looking leaves on Oncidium

[estación seca]

Let's be more specific. I meant, what are the temperatures in the growing area? If it's been kept at 78 F / 25.6C that is fine for Oncidiums, and this is another problem. If it's seen 100 F for multiple days I would say that's the problem.

Misting is rarely useful outside terrariums. It evaporates right away in low humidity environments, and promotes leaf fungus in high humidity environments.

Can you post photos of the other side of the plant, whole plant and the base? It looks like the worst foliage is on the new growth. Is that correct?

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[Imokira]

Oh I see. Yes I keep the area at 78°. It has been 100° outside. I can post more pictures. The worst are the leaves on the outside of the bulbs.

[Imokira]

Here are some more photos.

[Roberta]

Question... when was the last time the plant was repotted? The medium, and the roots showing on top of it, don't look great.

[estación seca]

What I meant was to turn the pot 180 degrees from the photo ending in 132004. I'd like to see what may be the new growth from the front, which looks like it's growing up against the edge of the pot on one side. Oncidiums tend to grow in one direction, and the photos you've posted have mostly shown the older parts of your plant.

How long have you had it?

[Imokira]

Originally Posted by Roberta

Question... when was the last time the plant was repotted? The medium, and the roots showing on top of it, don't look great.

I haven't repotted it before. I've only owned it for maybe 3 months.

[Imokira]

Originally Posted by estación seca

What I meant was to turn the pot 180 degrees from the photo ending in 132004. I'd like to see what may be the new growth from the front, which looks like it's growing up against the edge of the pot on one side. Oncidiums tend to grow in one direction, and the photos you've posted have mostly shown the older parts of your plant.

How long have you had it?

Oh I apologize. I'll post new ones that hopefully have what you're looking for in them. I've had it for maybe 3 months.

[Roberta]

That new growth looks good - and its growth indicates that this would be a good time to repot. (I find that most new acquisitions need it... Nobody pays the grower to repot, so it is often the case that when a plant is big enough to sell, it has been in that pot for awhile.) I would not be surprised if older growths were rootless. But the new one will be pushing out new roots. So you'll have a chance to move it in the pot. Put the oldest p-bulbs right against one side of the pot to give the new growth, and subsequent growths the maximum space. If the oldest p-bulbs are shriveled, no harm in removing them to make even more room, but don't be too aggressive... those old p-bulbs, even if rootless, are the energy store that the plant depends on to produce the new growth so if they have any substance at all, keep them. You will have another opportunity to clean it up in a couple of years, when it's time to repot again - and by that time, the root system will have had a chance to recover.

[estación seca]

After flowering Oncidiums produce new growths from the bases of the pseudobulbs. Yours is doing that; the largest, mostly brown growth is a little older than the two smaller green ones that are still sharply pointed.

I'm not sure why yours is doing this. I've seen it happen when they are too warm, and also when they are left completely dry.

Any chance it was in a sunny window? Even in a 78 F house direct sun through a window could burn Oncidium leaves like this. Remedies include placing a sheer curtain between the glass and the plants, or having a fan blow on the plants to move heat off the leaves. When sun scorches leaves they turn brown and dry up, but the growth doesn't turn soft and rot. When high ambient temperature is the problem the whole growth turns brown and mushy, then falls over.

If you bought it in flower it has likely been in that pot for about 2 years. The old roots look OK but the medium is getting old. New roots are bright white with green tips, but old roots also absorb water.

Oncidiums generally need repotting about every 2-3 years, either because the medium breaks down, or they fill the pot with growth. When the medium breaks down and crumbles it fills up the air spaces, and suffocates roots. Oncidiums need a lot of water, but they also need air at the roots.

The best time to repot Oncidiums is when making new roots, which usually coincides with new growth - now. The current pot is about the right size for this plant.

Get some potting medium. Some people use medium bark, sometimes mixed with other things like perlite or sphagnum moss. Other people use pure long-fiber sphagnum moss. The watering schedule is different between the two, so you need to be careful to water appropriately for the medium. If you tend to overwater plants bark is probably better to use. If you tend to underwater plants moss may work better.

If using bark, soak it for a few hours in water to moisten it before the first use. Or pour boiling water over it, then allow to cool. If using sphagnum, it should be just barely moist, so it doesn't feel crisp to your touch. You should not be able to wring out any water from it.

When you repot, gently shake off the old medium. You could also swish in a bucket of water. Don't be meticulous; you don't want to damage old roots, which need to function until new roots grow to provide water.

Wash the old pot in soap and water, and rinse.

Set the plant so the oldest part is a close to one edge as you can get it, with the new growths pointing towards the other rim. The root mass might make this somewhat difficult. They tend to climb a little with each new growth; I would repot this one a little deeper than it is in the pot now. Backfill with your medium.

If using bark, tamp it down gently but try not to force it and break roots. Note how heavy is the repotted plant dry. Water thoroughly and note how heavy it is wet. Place in an area where it gets bright light, but the leaves won't sunburn. Pick it up to check the weight day by day, and water again before it gets to the light, dry weight.

If using moss, pack the moss tightly enough for the plant to stand up. After repotting run water over just the top of the moss for a second or two. You are not trying to drench the moss, just get the top wet. The water will diffuse through the moss, leaving it well-aerated inside. Then water when the top is just going crisp. Situate as mentioned for bark repotting.

[Shadeflower]

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Originally Posted by Shadeflower

I always start my diagnosis by inspecting the state of the roots. Most of the time the roots will have gone mushy.