dendrobium thongchai gold: yellowing leaves with spot
 

I bought this orchid before it began blooming from a plants sale at the conservatory at my university. I didnt have any problems with it until the flowers faded and the spike died back (after flowers bloomed for over a month). It is potted loosely in miracle grow orchid mix (all I have been able to find so far in my area) and sits atop an improvised humidity tray. I lost a leaf today, it was yellowing and developed a dark spot and fell off when I touched it. I am new to growing orchids, but I am in love with them. Please help me save this guy!

I'm not able to post photos or links to photos without the post being denied, any ideas why?

I will private message the link to photos to anyone who replies and asks for it, until i get this figured out.

Some dendrobiums shed their leaves. Do you know what kind it is?

Have you made the picture file smaller before uploading it? It needs to be made a small size for posting here. If so I will find you a link called how to post a photo or something similar which gives instructions how to do it.

Okay, I found the link on how to post a photo. Here it is:

http://www.orchidboard.com/community...ng-photos.html

I'll try again with resizing, but that still shouldnt affect posting a link...

It's a Dendrobium Thongchai Gold "Yellow" via the tag when I bought it.

I don't post links, so can't help much there. I added the link on how to post photos in my previous reply. I'll add it here again:
http://www.orchidboard.com/community...ng-photos.html

It likes warm temps and quite bright light. I'm not sure if it is Miracle Grow but one of the store bought orchid mixes is to soil like and doesn't provide good aeration or drainage. I have one dendrobium with simialr parentage to yours and I do get some leaf drop. Maybe someone who grows this or more Dens will chime in

Here is what I found in OrchidWiz on this hybrid:
50%-60% humidity. Keep moist in the Spring-Summer, when plant is in active growth. Grow in a pot with porous, free-draining media. The pot should be small for plant size. Fertilize weekly, weakly (one quarter to half the normal dose). Reduce water/feeding during the cooler months. Common media: fir bark, coconut chunks.

Your plant is not dying. Your media mix is just fine. It is also a Dendrobium phalaenopsis type....so the culture should follow that....since it is a hybrid and warm growing, the winter rest must not be drastic .... if youre watering every other day in summer ....in the winter you water it every week...move it to a brighter window....wait til the media is dry and then water it....this is the time for growing new leaves and roots....
the leaf has fungus(the picture you posted with a black spot on the leaf; notice the yellow ring around the black spot=it is fungus) and I think it is partly the cause of the yellowing and falling of leaves....wipe leaves clean with cotton swab dipped in brown listerine every other day or wipe it clean with hydrogen peroxide or you can alternate it....or the plant just have old leaves and need to shed it....because I saw the other leaves=do not have black spots

As with your other post I would get it out of the Miricle grow mix. Your two plants you have posted are epiphytes. They grow on trees with their roots exposed to the air. Your mix contains a lot of peat and it isn't good for most orchids. It doesn't allow enough air to the roots. Miricle grow needs to sell this mix differently! You need to get a new mix.

I notice on the one leaf that it has a ring spot on it. You may have a fungal infection on your hands. Somewhere on this site someone managed to stop it from spreading as it can be deadly to the plant. I don't want to be an alarmist since the rest of your plant looks quite healthy, but that is a classic spot.