Yellowing on Rossioglossum bulb?

[sand_tiger86]

I checked my Rossioglossum Rawdon Jester today and one of the pseudobulbs is yellowing. I have no doubt the leaves will fall off now, which really pisses me off because it's only got two pseudobulbs with leaves and the new growth it does have is growing at the speed of snail. I suspect it might be too hot for it, being in a western window in Texas, but I really don't know of anything else I can do for it. I was really hoping I'd be able to slide by with it, as I've heard they're not as finicky as their Grande parent. I always have a small fan blowing on it, as well as the ceiling fan in the room going all day...and I simply cannot afford to leave my air conditioner on 70 all day long. Or is this just normal behavior for these things?

p.s. sorry for the sideways picture. For some reason my phone always uploads the damn things that way.

[Susie11]

I don't know about the yellowing but when leaves go yellow it is often a sign of too much light. I have the 'finicky' grande type and I have only had it for about a month but so far so good for me. I have noticed that the new growth is putting out new roots and the leaves are growing. I don't have mine in the windowsill but about four feet away and in a semi shaded location. I grow mine in bark mainly with a bit of moss for moisture. I hope that yours makes it as they are truly lovely plants. Good luck.

[Brutal_Dreamer]

Might you be over-watering it, Kelly? I see it is growing in sphag - just a thought. How are the roots? Everything okay inside the pot?

cheers,
BD

[sand_tiger86]

I probably need to take it out and check. I don't see any way I could be overwatering it, though...it's not planted in Sphag, it's in bark but has a layer of Sphag on top to conserve a bit of moisture. It dries out every day, but I water it twice a week. Maybe the problem is underwatering? The roots are definitely not plump like they used to be (I can stick my finger in the bottom and feel them). Maybe I should actually repot it into pure Sphag? I don't know...these Oncidium types really get me and I've never been able to grow them well. Especially this particular one because it needs high light but very mild temperatures, and you just don't get both here in Texas. I'm suspecting it's just getting overheated in a Western window. It hasn't put out one new root as far as I can tell, and I've had it for two months now.

[Magnus A]

I do not grow this one but I have a suggestion on what may have happend. the discoloration look to be started in the joint between the leaf and the semi-bulb. can you have got water in there and therby started something? fungusinfection, rot or something else? I have seen similar damages on two leafed cattleya´s before the leafs open upp full. They then form a sort of funnel that divert water down to the bulb top.
Is this the oldest semi-bulb of the two?

[Susie11]

I would advise against sphag because it stays too wet and if it is already suffering root rot then that is a sure way to send it to Heaven. I would check the roots and repot into a medium bark, perlite and charcoal mix which will dry out faster and promote growth as you will have to water more frequently but before watering make sure you need to water by testing with a finger inserted into the medium first. That is how I water mine. If in doubt don't water but if it feels dryish then do. Good luck on the repot.

[coeruleo]

for california growers, this is listed as temperature tolerant, but our 'hot' weather usually is only a week or so, maybe a few weeks at a time. i don't have this one, but the yellow spot looks like sunburn to me. sorry, not much help here, other than to say, keep an eye on it. this one might suffer a little during summer, but hopefully it will spring back when the weather cools. maybe it needs more humidity?

[sand_tiger86]

I think that's the problem. Everything I've read about this plant is contradictory. Some say let it dry, some say keep it moist. Some give it very bright light, some say a little above Phal. light. Some say it doesn't like a lot of humidity, but others say lots of humidity. I honestly have no idea what to do with it, as nobody seems to have steadfast culture on it like Vandas, Catts, Phals etc.

And I don't see how it could have root rot, as it essentially gets bone dry by the next day after watering it and I water it twice a week.

[Teena]

Oncidiums do lose their leaves to become pseudobulbs. I would suggest either moving this a little further away from the window, perhaps right or left of it so it is in much more indirect light during "high" summer months so it's not getting so hot during the day. Maybe letting it have morning light when you are home on your days off from work. You can give it a good soaking in tepid water that has some orchid food in it and talk to it, it likes the CO2 from your exhale, remind it that you really do like it and are trying your best and it has to meet you halfway. Those are good size bulbs on it, so I wouldn't worry about too moist, too dry, unless it gets blistering hot inside your place I would water it about once a week, you could also put it in a saucer with pebbles and some water in it to increase the humidity underneath the plant without letting it sit in water. Good luck - martha

martha

[orchidsal]

It's hard for me to see exactly how yellow that pseudo-bulb is, but diagnosing something like this long distance might very well be wrong of me and not helpful to you. I don't know that any of the orchids have 'steadfast' cultural requirements. Even the better advice from those with much experience can only really give general guidelines. Unfortunately there is plenty of contradictory information out there on just about everything, especially on the Internet, but it is not just on Rossioglossum Rawdon Jester (though maybe a bit more confusion). I am sorry I can't help more other than to say that you will have to experiment for yourself and if you need to make changes hopefully it is within your power and budget to do so. I honestly hope you succeed with this orchid. AL