Question
Hello Wayne,
Thanks for volunteering.  I purchased my 1st orchid about a month ago.  I think it is a  Phalaenopsis (no tag).  It has been in a north facing greenhouse window in an (window) air conditioned kitchen.  It has developed smaller than a dime, circular black spots on one leaf along with black down the center of that leaf and now a  second leaf has one spot on the tip.  I have moved the orchid to my office that is on the same side of the house but is not a greenhouse window and is not as bright, cool or drafty but I would like to know if you can tell me what is causing this and have any suggestions that would prevent further spots. -- Jacque Wallis

Answer
Thanks for your question Jacque.  My guess is there is one or two likely causes of the black spotting.

In the summer, the sun is at its maximum northward journey.  You may have noticed whether or not you have received any direct sunlight in this window.  If so, it is possible that a concentrated beam of sunlight burned the leaf.  The black spot would be dry for a burn.  While unsightly, this alone would not be a threat to the overall health of your plant. I would use a clean razor blade to remove that portion of the leaf that contains the spot.

The second, and more serious cause, is a fungus infection.  This can come about if the plant has had water standing on the leaf overnight.  Always water your plant in the morning to allow time for drying before nightfall.  Also, try to minimize the amount of moisture that you get on the leaves. A small fan in the vicinity to provide a small air movement will aid in drying and be beneficial in general.

Assuming you have an active fungus infection on the leaf, or to prevent one from occuring on those blackened areas, you may try swabing those areas with such home remedies as cinnamon, listerine, or sulphur.  There also are commercial fungicides you can get at your garden center such as "banrot".  If you take the commercial route, your garden center nursery person may be able to advise you about the best product.

Overall, I would advise keeping the plant on the dry side for a while and hope there will be no further development of black spots.

Finally, I am always concerned about the status of roots in the pot on newly purchased orchids.  You may want to locate a retailer who carries bags of orchid potting mix.  Keep one on hand because an annual repotting is desirable.  I would unpot the plant and check its roots.  If any are "mushy", remove that part of the root before repotting.  Healthy roots are the most important factor is having a healthy plant.  In repotting, your new mix will be very dry, so may want to soak it for a few hours before use.  Try to keep your plant in the 65 - 80 degree range.  An occassional 60 degree or 85 degree temperature will be ok.