Question

Orchid leaf   QUESTION: Hi Wayne,

I have a Phalaenopsis orchid and there is a dry looking spot with black in the middle on the leaf. I attached a photo. I have spayed it with fungicide (white spots), but I am not sure if I am doing the right thing. Would you know what caused this spot? And if something that can spread what should I do to stop it?

Thank you.
Katalin

ANSWER: Katalin, thanks for your interesting questions.  Your photo came through a litle dark but the spot to which you were refering is visible.  My first impression is that it is sunburn. Since you mentioned that the spot is dry, that further supports this preliminary diagnosis.  Because any leaf damage constitues a weakened defense, it is an invitation to future fungal or insect attack.  For this reason, I recommend making a cut across the leaf about 2 CM below the affected area and into healthy tissue (removing the affected part of the leaf).  Then, seal the cut wound with powdered sulphur or a sulphur compound found in some fungicides.  Hopofully, you have several other healthy leaves.

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QUESTION: Thanks Wayne. :) I do have one more large healthy leaf and and a new one growing that is about 7-8cm tall and a few new roots. I am hoping this would be enough for the plant to survive if I cut the affected leaf. Is that right? I will cut the affected leaf as you said to be on the safe side. :)
Katalin

ANSWER: The other leaves should be enough.  I would retain the healthy portions of the affeced leaf if possible for additional photosynthetic activity.  We didn't discuss repoting of the plant so I hope that has been done in the past year or so.  Fresh potting mix and healthy roots will give your plant a boost. Repotting will give you a chance to examine the roots to ensure that all are healthy (ie firm) as you unpot and then repot.

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Orchid plant   QUESTION: Not sure when was this re-potted as I only have it since October, when my husband bought it from an orchid nursery.  I have cut the stems after it flowered and the new leaf grew since then. I have been reading (from your previous answers to other people as well) that it is good to re-pot after flowering, so I have been contemplating this for a while. I have a coir block that I was thinking of using. I took a photo of the plant so you can see what it's like(there are also two green roots sticking out at the bottom on the other side of the pot that are not showing)and if I should re-pot.
Thanks, Katalin

Answer
Katalin, the potting mix on the surface looks new so it must have been repotted just before purchase.  I don't think, therefore, it needs repotting at this time.  Orchid roots also are sensitive to their environment.  If, in the future, you want to switch to coir, I would do it gradually, braking up the coir block and mixing pieces of the coconut fiber in with the fir bark at first.  Eventually, if you want to grow it in coir, you can increase the proportion of mix that contains coir, until it is finally all coir.  I have found that not all plants take well to the coir, so gradually introducing it will give early indications as to how the plant is adapting to it. Coir helps to keep the mix open as it tends not to decay.  In that, it serves the same function as charcoal, tree fern, perlite, lava rock, etc, all of which serve to keep the mix "open" when fir bark turns to soil.