Rec'd this Hibiscus in the mail today (12/8) and couldn't understand exactly what was lurking on the undersides of the bottom leaves. Does anyone know? Where the leaf meets the stem is black--it's not dirt as I tried rubbing it and it doesn't come off. --perhaps mold? Since the search function is disabled, I couldn't research before applying this inquiry, but any input would be much appreciated.
It did come from what I thought to be a pretty reliable source. Thank You, Snug
Here's another pic. The black stuff is actually on two bottom leaves.
I'd keep an eye out and see if it gets worse--if the plant at one time had aphids/scale/mealies then the honeydew they leave behind often leads to sooty mold which can be very hard to clean off a plant even after you've taken care of the bug problem so it could just be something like that.
I agree with ecrane3 that it looks like sooty mold.
"Sooty molds can also grow on exudates produced by glandular trichomes on leaves of some plants such as Catalpa, Hibiscus, and Juglans species."
Copied from this link... http://na.fs.fed.us/spfo/pubs/howtos/ht_sooty/ht_sooty.htm
Ecrane3 - Dave,
your observations and comments are certainly appreciated. I did a bit of googleing last night and came up with the same conclusion that these black blotches may very well be mold. I am going to isolate this Hib from the rest of my Hibiscus plants just in case. It looks like this plant was attacked by a bug in its earlier life. It appears that some nurseries sell plants this way--as long as the Hib is viable when they ship it. In any event, I hope the "intensive care period" is over and it's on its way back to health. Thank You, Snug
Sooty mold isn't like real mold...it only occurs where there's sticky sweet stuff like the honeydew or the exudates that Dave mentioned. It won't spread from plant to plant like other types of fungus might (unless that other plant also has the sweet sticky stuff for it to grow on, in which case it would probably end up getting it all on its own anyway). And assuming you got rid of the bugs that were excreting the honeydew, the mold itself doesn't really hurt the plant, it just looks ugly. I suppose if you had enough mold on the leaves that they were completely covered then it might interfere with photosynthesis, but the little bit that you have is no big deal. Personally I wouldn't fault the nursery for shipping it like this--as I mentioned it's pretty hard to get the sooty mold off, so as long as they took care of any aphids, scale etc before they sent it to you I don't think they did anything wrong (and since the sooty mold could have grown on things excreted by the plant itself there's not much they can do about that--it's going to happen sometimes).
ecrane3, thank you again for your comments. So far the new leaves on the recently purchased hib seem to be fine, and as long as the plant continues to maintain its health, I won't sweat the small stuff. I gave it an upper- and lower-leaf spraying of Neem as a preventive--so far so good. Thanks! Snug
