Phalaenopsis: Black spot on leaf
 

First, let me say that I have been enjoying reading many of the informative threads on this site. Thanks for all of the valuable information. Now for my first post. One of my phals has a black spot on just one of its leaves. This developed more than a year ago now and does not seem to effect the overall health of the plant. Many new roots have developed, a new leaf has grown over the summer, a second leaf is developing now and a new spike is beginning. Also, I just cut the old spike down to one node and I am seeing swelling from that node and it may send out new growth.

My question: what is the cause of the black spot and should I cut that leaf off the plant or leave it alone?

It looks like mechanical damage or an old infection that is no longer active. You can leave it alone. The rest of the leaf looks very healthy and will help in providing energy to the orchid.

It could also be sunburn. Just a few minutes in your car with the sun shining through the window onto the leaf could do that.