Yellowing leaves on Zygopetalum Mackayi

[Orkidea]

Dear OrchidTalk Members,
Can you help me to figure out why relatively recent leaves are turning yellow on my Z. Mackayi. See some pictures below.

I have had it growing in a clay pot in the mixture of med-grade bark, perlite and charcoal. It's in a bright spot but not in the sun. Nighttime temps are around 15C, daytime around 21-23C. I have watered it with tepid water when the top layer (3 cm) of the medium feels dry, which is starting to be every 5 days here in the NZ spring. My orchids get some weak fertiliser solution in 2-3 waterings and then 1-2 (or several) without any. I checked the roots and found no rot. It has new growth appearing and the pseudo-bulb seems healthy. The same kind of yellowing happened in the fall with a fairly new leaf. Only thing I thought I could change was to bring it to a bit warmer & brighter place as it was getting a lot of spots. It seems not to have helped as the problem and the spots persist. Today I added a tiny bit of sphagnum moss around the roots to ensure that they don't dry too quickly as the clay pot is not very big. Zygos beside it don't show any signs of distress!

Any advice is most appreciated! Thank you in advance!

[gardenguysorchids]

I am glad you posted this question as I am having a similar problem with my Zygo "Jumping Jack". The leaves on the center growth are turning yellow and then getting brown. This growth is about 6 months old. Two newer growths are fine and the one has a nice strong spike. Am looking forward to the replies/advice you receive.

[stateless]

Zygo's are not the most attractive foliage orchids, the roots look good, it's putting out a new growth, but the leaves look really bad. I hope someone else can help.

[cdayinflorida]

They are over-potted. I would reduce the size of the pot by more than half. I would also spray with a good fungicide.Good Luck!

[shirleycox]

Zygopetalum species and their hybrids are very gragrant and easy growing orchids. They fall in general category of 'soft leaf' orchids because of their leathery strap like leaves. I believe that light is the most important factor for these orchids to grow well. Dark leaves indicates they get a too little light, while yellowish green leaves are a sign of too much light. Adjust your lights but careful when adjusting your light exposure, because the leaves will burn very easily if over exposed. They do well in a bright window but away from the direct sunlight.

[Orkidea]

Thank you for your replies. I'm really at loss with this one. It was good to hear that others have similar problems with their Zygos. I hadn't yet considered repotting it to a smaller container. Thank you Cathy! That's my next step. Shirleycox, thank you for your suggestion too. However, I don't think light is the problem. I keep all of my Zygos together and others have beautiful light green leaves with very little or no spotting. New growts and roots are also appearing. They were in a slightly darker place prior to moving them to the current location and it didn't seem to help with problem. The current location seems better as my other Zygos appear happier.

I continue experimenting.

[shirleycox]

Do you mist your orchids? These Zygos have very sensitive foliage and are prone to fungal issues on the leaves when misting. They love air movement and also higher humidity otherwise the leaves will crinkle as they emerge. Spray them with Bayers Rose and flower spray.

[cdayinflorida]

One of the easiest remedies to bump up the humidity is to set up a cool mist humidifier. They can be picked up cheaply at a thrift store. I've bought several and most of them were new in the box for about 10.00.

[Brutal_Dreamer]

They are over-potted. I would reduce the size of the pot by more than half. I would also spray with a good fungicide.Good Luck!

I agree. I would be concerned for the roots in that large of container.

cheers,
BD

[Orkidea]

Thank you all for your responses.

I took the plant to our orchid society meeting. They think it's a virus and recommended destroying it... very sad. It has beautiful roots, bright green new bulb, new growth - but like before, I expect the leaves die soon. I think the orchid society members are right because all of my other zygos are doing well. I haven't thrown sick zygo out yet but I repotted it to a small plastic pot and separated it from the other orchids. I want to see the yellowing happen one more time before I toss it. I would like the virus-diagnosis to be wrong.