Yellow on cattleya pseudobulbs and leaves
 

I am a beginner forum member and a reasonably new orchid lover. I have a shadehouse with about 60 cattleya and still have so much to learn. I have been really pleased with how they are all growing and responding to date, although I have now learned that my shadehouse needs to move to a full sun position so I will tackle that big job when I can. This is the first real problem I have encountered. I went in to 'talk' to my orchids a few days ago and was alarmed at the yellow on some pseudobulbs and a bit of yellowing on the leaves. I have racked my brain and I think I may have been using a stronger than recommended dose of fertilizer. Could this be the problem? It is all that I can think of however not all of them have this problem and my 6 phals. that live on my back deck have not showed any ill signs and neither have any of my others (4 vanda's and about 10 dendrobiums). Any thoughts would be much appreciated.

Hmm from the last photo it looks like the base of the pseudo bulbs are black too. You may be having a fungal problem which happened to me and my cattleya from overwatering and not letting them dry out. They need a bit more sun than phals and I have learnt the hard way about the watering. Treat them w fungicide and cut back on the watering and fertiliser. The fertiliser could be contributing but the black spots and the yellow bits look like fungus. Any more expert views?


Sent from my iPhone using Tapatalk

Make certain that they are getting enough calcium and iron. Also, as already said, take care to make certain that the medium dries quickly. Good luck!

Cattleyas need to have their roots dry out. I'm not sure those pots will allow the roots to dry which could mean root rot.

Firstly, thank you very much for your help, I do appreciate it.

I knew very little when I first started and I realise that my pots are less than ideal, I was thinking of repotting after this winter which is almost upon us as I would expect they would have flowered (hopefully) by then, they are not really due for another year but thought it best to get them into better pots and I also think I could do with a better medium than the first batch as it is a little fine and I have found that a medium with a bit more bark or coconut husks is better for their drainage. I certainly have backed off on fertilising and watering although we have had a lot of rain of late so that is beyond my control.

I think that mostly, the black that is seen is where I have not peeled off the sheath (if i have my terms correct) but I certainly will put a fungacide through as I do have a little moss around as well. Do you always pull off the sheaths?

Thanks again.

I am glad you backed off on fertilizing. Catleyas do not need much fertilizer. They need lots of sun, I would say nearly full sun, but about 25% shade. They need water also with good drainage. Water and sun create the carbohydrate sugars that are stored as food, and that create additional growth. Fertilizer only tweaks the chemicles a bit, but it dosent matter if you water them with fish tank water as some do, or get a fancy mix. I actually found a formula online, and make that using ammonia, beer and superthrive. They are growing just wonderfully.

I am not sure your plants will want to wait for new pots and media until after winter. It's hard to tell for sure from pictures but if the ceramic one has no other pot inside it with good drainage, it may have root rot before winter is over. I would get suitable pots and potting media as soon as you can and re-pot them now with as little disturbance to the roots as possible.

OK, thanks again. I will certainly repot asap in better pot sizes and better medium. I also take onboard that fertilisers are a science as well!!! I did purchase mine from an Orchid Show but I probably need to do more research down that road. Thanks again.

Your pot sizes look OK. They don't appear to have any or enough drain and aeration holes. There are lots of orchid pots avaialable online from places like repotme.com, or quarteracreorchids.com and similar. Choose a pot size that fits the roots and leaves a little extra space for a year or two of growth. Do not over pot them. I like clear pots with good drainage and then you can see how things are doing in the root zone. The roots seem to like the clear pots also and possibly photosynthesize when sunlight is available.

A general rule for fertilizer is to use a balanced one and dilute it 1/4 to 1/2 the recommended strength on the container. Ferilize 'weakly weekly' and once a month flush the pot with clear water to remove any accumulated fertilizer salts.

It can be a balancing act. The more sun they get, the more fertilizer they need. The more sun and fertilizer and sun they get, the faster they grow. When they grow faster than they can make chlorophyll to support, they turn yellow.

You can slow down the metabolism by reducing light and fertilizer, or you can add additional Magnesium from epsom salts (Magnesium sulfate). I alternate between 1/4 strength commercial fertilizer and a mix of 1 tbsp Potassium nitrate with 1 tbsp Magnesium sulfate per gallon.