I have a rhizomatous begonia which is not doing well. As each new leaf matures the area where the petiole joins the leaf turns brown and then eventually the whole leaf dies. I have it potted in a loose, well draining soil, don't overwater or overfertilize. I have tried leaching the soil, but nothing seems to help. I even tried taking a cutting and starting a new plant and the same thing happened with the new plant. Does any one have any ideas about what might be going on?
Could be lack of humidity. Could also be draughtly conditions. Could be too much heat if the leaves were dry and curled. Too much water if leaves are wilted and rotten. There are a lot of rhizomatous begonias, some very tempermental. You wouldn't happen to know which one you have? Rhizomatous, and other types of begonias, go through a dormancy through the winter. Sometimes it's a very pronounced dormancy. Here on the coast, my rhizomatous begonias do not go through as pronounced a dormancy as when I lived on the prairies. Sometimes the abortion of leaves is not unusual, but not, say, June through October. They are also quite against being overpotted - or put in a pot too large for the rootball. So, anything sound familiar?
I suspect it's too cold. Has this problem been going on all year, or come on recently with cooler seasonal conditions? Try moving to a warmer position.
Thanks for the replies. So far nothing seems to pinpoint the problem except maybe the dormancy issue. I had the begonia growing in an enclosed porch for the summer and then moved it under a light unit for the winter. Perhaps it wants to go dormant and I'm not letting it do so. However, I do have other begonias growing under the same conditions and they will go dormant when they are ready, lights or no lights. This is the only one showing the browning problem. Maybe it is just a tempermental variety..
It could be a nutrient problem. Probably not macro, but micronutrient. I'm just having a deja vu, but I could be wrong. I did some research on a houseplant some time ago, that was having problems with the new leaves. As memory serves, it had something to do with boron. Try googling boron deficiencies, or other micronutrients and see what you get. Just a thought...
I too thought that it might be a nutrient deficiency but it is certainly difficult to pinpoint the exact cause since none of my other plants in the same or similiar soil mix are showing any problems. I did find one website that looked to have some good info. Here it is: www.mgonline.com/fertilize.html. This site suggests using fish emulsion as a fertilizer since it contains more micronutrients.
Well, just fyi, when I did take the advice I had read, and add fertilizer with micros, it didn't really help the problem with the plant. Was worth a try anyway. Have you tried watering with rainwater?