Cool, damp conditions make the conditions ripe for powdery mildew to spread. Spray with a fungicide to keep mildew at bay. Remove and discard worst leaves or all leaves if need be. Circulate warm air to keep leaf surfaces dry (but keep humidity high - yeah it is a difficult order to follow). If you don't want to fight this in the future you can get rid of begonias that have a high susceptibility to mildew or follow a good spraying program.
Lynn sorry I dont have a pic but the "mold" is small white patches on the top side of the leaves. They start small and get bigger til eventual the leaves shrivel. I've tried spraying w/soapy water to clean it off but I need something stronger
Try Neem oil (it has a strange smell so you might want to take it outside to spray). It is organic and you can get it at Home Depot, Lowe's, Wal-Mart, and nursery stores either in a ready to use hand sprayer or in concentrate form. Other fungicides should work too but follow directions carefully. Some home remedies are diluted milk, a baking soda mix, and Lysol aerosol spray for mildew (this may damage the leaves though). Sulfur or copper dust is supposed to work if you want to look for it and dust it on the leaves.
Here is what powdery mildew looks like on a cane begonia leaf.
You will need to try keep moisture off the foliage of your plants, some of these Begonias dont like water, damp or dew from cold conditions on the leaves as this causes the problems, I would do as suggested and remove any leaves that show signs of the mildew/mould, cut back on the watering of the plant and when you have to add water, then water the plant from the bottom by sitting in a shallow bowl of water till you feel the top of the soil damp, then allow the pot to drain before placing it back onto a saucer, if it is now indoors, new leaves may regrow depending on the type of Begonia, but if not, perhaps you will have to let it go into winter dormancy and restart it for next spring. good luck. WeeNel.
it actually sounds like Rhizoctonia, a common mold on begonias. At this late time of the season, you could spend lots of $, tear them up and chuck them because once they start and the nights are cool and the days too there's not a lot to do . Throw them out and get some pansies.
I "cure" mine that I am overwintering in the house by cutting them down to the top of the pot and shop vac. the debris out. Around februrrary I un-pot them, scrape some dirt off and repalce it with nice new stuff and give them another trim to about 3-5 inches. I only get the mold every year or so. My plants are 6 years old now.
I have to ask Why, why would you go through all that for a begonia. I'm not being smart or rude I was just wondering. I would do something like that just so I could see if it worked, then I'd pitch it.
Maybe the question should be "What begonias are you growing?" You are probably thinking of wax begonias but most on this forum are far from it.
Some begonias are very hard to come by and can be very rare. If begonias and I mean several hundred varieties in species and hybrids were readily available at any garden center each spring and were as affordable as a six pack of wax begonias, then yes I'd pitch them on the compost heap come winter and start over the next year (but if I have 300+ different varieties and paid on average $8 per plant, you can see that would become very expensive to replace each year) but since some of us order them through the mail or go great distances like conventions in order to find new ones then by all means I would do all I could in my power to save each and every one of them.
YOu know I never thought of that, do you find that each year the yeild is bigger and better from the year before or does it take such a long time to recover from the winter months that you just notice a little yeild?
For me there is no comparison. The older they are, the faster they respond to the March warm-ups and the faster they get real big and bushy. I usually trim them back a little in July since I need cuttings and to make them bushier for the fall winds around here.
hcmcdole, you know you sounded a little preachy. I was thinking of wax it was the first thing that came to my mind. I know very well of all the other varieties having grown many of them myself at the greenhouse at my college where i spent 6 years playing with them. Most people on this forum are beginners and why would they think unlike me. So, why be snippy to me ? I wasn't talking to you to start with I was truely courious as to what nanbernier was doing with the plants.
Oh, and Kitten, You will find that even the wax will thicken up 'till the stems fill the pot and with all of those roots, well they become a proven focal point plant. I have one wax - red leaves and flowers, that I have done this with for a couple of years and it is well worth the little bit of space and trouble to bring them in for the year. And if I put it in a room with sunlight and average home temps, they bloom non-stop all winter long. Can't beat that.
So, in the winter you bring them inside. I know how to water, fert etc.. but there is nothing better than to talk with someone who has done it for years becasue they have hit all the trouble spots at least once. So, with that do you fertilize them in the winet? Rule of thumb is no but I usually do when I bring mine in i find they bounce back better. And what about bugs?
Weak fert. maybe 1/4 to 1/2. I fertilize more in early spring, and, once they go outside, it's weekly. I have only had bugs on the houseplants that go outside for the summer. So far, Safers insecticidal soap has worked for me.
3-4 inches long/ rooting hormone/soiless mix. I have taken cuttings of some plants that are marginal for my area and potted them up already. Towards spring I will take cuttings of those and others that I want in the gardens and then in June or July I will do some to fill in where I've got blank spots.
Cane Begonias like Angel Wing or Dragon Wing are very easy to keep all winter.Sometimes I keep them upstairs like a house plant and other years I keep them in the basement under a shoplight.They bloom all winter with minimal water and no fertilizer.I cut them back in spring,feed them, and put them outside again.Mine are at least 6 years old.
So far,I have never tried my Rex or Rhizhomous Begonias outside,because I don't always have time to check them for water,food,insects,frequently enough.
Here's another old time Begonia grower, I love them like babies, every year they do their stuff for me with very little returns from me, but every year they get bigger and better, this year has been an exception, the flowers are like saucers, I always remove the smaller male flowers as they for either side of the lovely female flowers and this helps to make the flowers even larger, Like said before, I leave mine in the pots till next spring when I see the tiny bud eyes start to form, then I re pot them into nice new compost till they are ready to go outside on hot days, dont have as many as Hcmcdole, but I bet these are a site to behold, Good luck WeeNel.
My DS lives in Fort Worth, TX and has had his wax B's overwinter in the flower beds with just a light woodmulch. They have frozen down to an inch or so tall and then come back bigger and better. They had been in 4" pots when first planted, now they are gallon pot sized(2 1/2 years). He was stunned but happy that they were there in springtime as he hadn't planned on them surviving the winter.
I had forgotten a pot of them one year and they ended up in a tower of large pots of dahlia bulbs in my garage. I think I watered the stack in December and early March. ( each pot got a bit of water in one side of it) In late March I spread the pots out in front of the windows and found the begonias were still alive! and growing! I think they are wonderfully forgiving as long as they are not overwatered.
Here is a cool way to propagate begonias. Aluminum baking pans from the grocery store with plastic lids make a great community pot. Everything is fair game to go into the pans. This pan has semperflorens ('Lady Carol', 'Lady Francis', 'Cherry Blossom', 'Charm', and some other unknowns) plus a cane 'Pink Minx', unidentified species U501, another species - bipinnatifida, and several rex leaf cuttings of 'Silver Dollar' have all grown well. Poke holes in the pan, spread good potting mix, water lightly, stick cuttings (no rooting hormone), cover with lid, and let the growing begin.
That's a great site.
Unfortunately in my zone we can only do this if we have a greenhouse or a very extensive light setup.
They are so beautiful,but it requires a lot of time and effort if you can only put them outdoors in the summer.Sigh...
That is such a beauty, we call them lace edged flowering Begonias here or some folks call them frilled edged, I had a white one 2 years ago just like that but didn't get it inside fast enough when we got a really early frost, what I have to do with those types of Begonias is (like dahlias) let the foliage die back, remove it and then leave them to dry out in the greenhouse, then early spring, take them from the pot/soil and set the corm/tuber out in a tray of nice new damp compost till I see the little eye buds start to pink up, then I re pot them into their final pots to grow on indoors till the weather is warm, not too many warm days here this year I hate to admit, but I can just bring them in and out when the weather is right, no problems doing that at all, outdoors helps to strengthen the foliage, indoors it tends to stay softish, but worth the effort I can tell you.
Good luck with all your wonderful Begonias, they are a summer treat for me. WeeNel.
Last year when I did all fifteen (or more) of my outside planters I didnt spend a penny. I have a grrrrrr8 window (plus a coldroom that's never below 45 a sunny attic that stays @50 so I can duplicate nature to an extent.)where I winter them.
I. save some because they are unique...
like the new variety that thrives in the sun. Most of them dont give me the mold issue .The common begonia and the angel wings are the best...I have one pot of angels that I've brought in and out for five years! They slow down over the winter and I fertilize them just before they go out. They ussually break into profuse blooms within a week! and they are 12-15" high so they really impact the spring show.
Thanks again...the first pot I cut back and cleaned is already recovering!
I know what you mean about the extra trouble taking them outdoors - it is well worth it. They grow so much better despite all the things that may (and often do) go wrong. Show us some pictures of your beauties.
You are right about mold on some begonias and not on others. Most of my begonias I have no trouble with mold (mildew), but rexes and thin leaf canes (those with U062 genes) give me absolute fits but I still grow them despite their imperfections. I should start a rigorous spraying program next year since it is too late this year. If I keep the cane or rhizome alive, they will flush out with new leaves. I often cut off infected leaves and if they are not too bad, use them for propagation.
Rexes are outrageous for color so even if they end up on the compost heap, they're still worth it. I cut most of the leaves off of these new ones and started them in a propagation tray. I hope most of them take.
I don't have a lot of them right now,but when I used to grow them under lights I propagated a lot.The method that always worked best for me was cutting the veins and laying the leaf flat on a peat/perlite mix.I kept the top of my box covered and the soil just damp.
I read an article that if you don't know exactly what you are dealing with when a flower is dieased is to get a spray bottle and mix 1 part bleach and 4 parts water and spay the leaves under and on top and they said it should take care of any thing that was wrong. Edit:
Oh I forgot too that they said you could use an epson salt mixture of the same portions and spay them with that too.