Questions on: Begonia

Ron Smith, Horticulturist, NDSU Extension Service

Q: I think I have a rex begonia. It has large, colorful leaves and no flowers. It seems to be doing well except that recently two or three of the leaves became bleached. All the other leaves look healthy. It has a southwestern exposure. (e-mail reference)

A: The southwestern exposure could be the problem because the plant is getting too much direct sunlight. Try moving the plant to one side or the other to avoid direct sunlight. It won't cure the affected leaves, but should keep other leaves from being damaged.

Q: I have an angel-wing begonia plant that I started from a cutting about 3 1/2 years ago. I've started several other plants from this plant and put them together in a large pot. They never have flowered. It is located in a very "happy place" on my kitchen island under a skylight. The plant grows like crazy! I water it every other day with at least 1 to 1 1/2 cups of water. I've heard that the flowers are very pretty, but have never seen them. Should I let it dry out between watering? I tried an experiment by breaking off a leaf, rooting it in a glass of water and put it in its own small pot. It has sustained its own little life without sprouting any other leaves or canes. Have you ever heard of this? Will it be an eternal leaf? (e-mail reference)

A: Yes, it will be an eternal leaf. If you take the leaf or another one and lay it across the media, while making small slices across some veins, new plantlets eventually will grow and the original leaf deteriorate. I am surprised that this has not happened at the base of the leaf you have stuck in the water. You are overwatering. You must have good drainage or you would have rotted everything a long time ago. Allow the soil media to dry before rewatering. This should slightly stress the plant enough to bring it into flower.

Q: I recently received a begonia, which I repotted and placed in front of a sunny window. Over the past couple of weeks, it has been flowering profusely, but its leaves have begun to shrivel. It is producing new leaves, but even some of those are withering. It has plenty of water. In fact, I believe I have overwatered it. (e-mail reference)

A: Sun and begonias usually don’t make a good combination. I would suggest moving it to the side or back a little from the window so that it doesn’t receive direct sunlight. Also, keeping the soil media moist and keeping it wet are two different conditions. Moist is good, wet is not, so back off on the watering. If these two actions don’t result in some improvement, then it is something else causing the problem.

Q: I know nothing about plants except that God made them. I just bought a reduced-price begonia and put it in my office. When I bought it, there were many dead leaves around the base of the plant. I cut away the dead stuff. One stem looks thin compared with the offshoot, which is quite thick. It looks like it was eroded by the dead stuff. I have prayed over it and asked God to heal it. If that doesn’t work, should I try replanting the stem? If so, where do I take the cutting? God bless you. (e-mail reference)

A: Help sometimes arrives in unexpected ways. Perhaps your prayers led you to find our Web site! There are three types of begonias. Since you didn’t specify the one you have, I’ll give you the procedure for each variety. Tuberous begonia can be grown from their tuberous stems, as long as each one is bearing a growing point. Leaf, leaf-bud and short-stem cuttings also can be used. Fibrous-rooted begonias often are referred to as wax and Christmas begonias. It can be propagated by leaf and stem cuttings. Rhizomatous types, such as the Rex begonia, are divided or the rhizomes are cut into sections. These also can be propagated by leaf cuttings or stem cuttings. Go to for my publication on home propagation techniques. The publication graphically explains the procedures.

Q: I have been working with an indoor angel wing begonia for 10 years. I took a slip from my sister-in-law’s plant, which flowered abundantly. Mine has not flowered. From what I have read, the plant grows to about 3 feet tall and must dry out before watering. This is what confuses me. One of the stems on my plant is nearly 7 feet tall. It grows like crazy, but never flowers. I have it in a northeast window. On one Web site, I was told it liked very sunny or high-light conditions. On another Web site, I am told it blooms in the shade. I have been using a dry-blooming plant fertilizer, but still no blooms. I love the flowers that are supposed to be on the plant. Could you help me? (e-mail reference)

A: Angel wing begonias can be frustrating! It should be kept away from hot, dry situations or cold, drafty locations, especially at night. Do not overwater. The only sun it should get is early morning or early evening. I don’t know why your plant is not blooming. Try cutting it back or not fertilizing as much. It sounds like you are doing everything correctly, so it should bloom this spring. If it is a source of frustration for you, get rid of it and try another plant. Life is too short to be uptight about a plant not flowering!

Q: I just had a gentleman come in with a leaf from a begonia. He said it has a powdery, mildew substance on the leaves that is spreading to the other begonias. They are planted on the north side of the house. Any suggestions on what he can do? (Mandan, N.D.)

A: Once the powdery mildew fungus has hit, there is little that can be done except to spray a fungicide on the plants in hopes of keeping it from spreading to new growth and other begonias.

Q: Can I put my angel wing begonia outside? I'm not sure which side of the house would be best. South is probably too hot, but it's about the only side that gets decent sun. Any advice? (Park Rapids, Minn.)

A: Give the angel wing all the bright, indirect light available, but keep it out of the south exposure or it will cook. Summering houseplants outdoors is like going on vacation for most of them.

Q: I would like to know what to do with my two beautiful begonias this winter. Do they do well as house plants or can I leave them in the basement until spring? If so, how often should they be watered? I would also like to know what to do with about a dozen geraniums. I have them in planters outside, but have to bring them in soon. I am short on room so they have to go to sleep for the winter. Is it best to remove them from the planters and put them in brown bags until spring? (Summit, S.D.)

A: I am assuming the begonias you are talking about are the tuberous type. While they can be attractive houseplants over winter, the dry winter air is usually too much for them. I suggest, unless you want to put extra effort into their care, that you allow them to dry down and store the bulbs for the winter and repot them in March. With the geraniums, cut them back to about four inches, shake/knock off as much soil as possible and store them in bags or tied loosely with a string. Check monthly to see if they are withering. If they are, immerse in tepid water for about 20 - 30 minutes. Repot in February or early March.

Q. I would like to plant some begonias, but I want the kind that you dig up in the fall and it has bulbs under it. Can you tell me what kind of begonias these are and when is a good time to plant them? Also, what kind of flowers do you recommend for hanging baskets? (Brooks, Minn.)

A. The begonias you're referring to are known are tuberous begonias. You are better off purchasing plants from a nursery or greenhouse this spring and planting them out in the shade when all danger of frost has passed. In the fall, you can dig them up and store them dry in a cool location. Generally, you repot in early February to initiate new growth and produce flowers by the time late spring has settled in.

For hanging baskets, you might want to try one of the "wave" petunias. I have seen a purple wave hanging basket that was cascading with flowers!

Q. Enclosed is a leaf from my houseplant. I do not know the botanical name for it. We call it the angel wing begonia. The leaves develop these spots on them and then they dry up and fall off. I haven't been able to see any insects on the plant. In how much light should the plant be kept? Could you help me with this problem? (Colfax, N.D.)

A. The angel wing begonia is a member of the cane-stemmed begonias, which gives them, at maturity, bamboo-like stems with wide internodes. From the sample you sent, it appears as if you are growing the species Begonia corallina. Your foliage sample was showing evidence of mildew disease, which is easily managed with diligence. Try to move the plant where it will get better air circulation. Avoid wetting the foliage when watering or spraying other plants. Try to pick off and discard the worst leaves and begin a monthly fertilization with half strength water soluble material to encourage new leaf emergence.

Q. About a month ago my angel wing begonia dropped about 10 leaves each day for a couple of days, then it didn't lose any until the past two days when it dropped another 25 leaves. Can you tell me what the problem is? The plant is originally about 12 years old, but I have transplanted it several times. (Willow Lake, S.D.)

A. The leaf samples you sent are good enough to propagate. Thanks! Any type of leaf drop like you describe is the result of some sharp environmental alternative: water/no water, heat/cold, warm or cold drafts or bright, indirect light/low light. Check your cultural practices to see if any of the above is taking place, and correct. I hope this helps you solve the problem as it appears to be a beautiful plant, based on the sample you sent.

Q. Can you please let me know where I can get an oleander and an angel wing begonia? (Jamestown, N.D.)

A. Oleanders are extremely poisonous plants, and because of that, I do not suggest them as houseplants. They are used outdoors as hedges in the deep South.

For an angel wing begonia, I suggest contacting a local nursery, greenhouse or florist shop. There are several good ones in Jamestown.

Q. I have a tuberless begonia. I took off some slips, rooted them and put them in a pot. They appear really healthy, but they do not seem to flower. (LaMoure, N.D.)

A. Try not being so nice to them! Allow them to become potbound and a little starved. Then give them the morning light, and they should flower for you.

Q. I recently purchased begonias and gloxinias. I believe they are perennials, but don't know if they have to be lifted in the fall.  Do you have any pamphlets on what perennials do and do not have to be lifted? I'm trying to get a flower bed started with the ones that need no lifting.  I would also like some literature on what to plant where in my vegetable garden. I understand that some things do not do well next to each other, but don't know which ones. Why did my Yucca plant not bloom the last year or two? It greens up nicely, but that's it. Should I have cut back the leaves last fall?

Why don't the companies that package these perennials put the information I have requested on the package? All they state on the package is the planting method and whether they are annuals or perennials. Some don't even give that much information. (Orient, S.D.)

A. A lot of questions! Plants that are perennial in zone 3 or 4 (N.D. and S.D.) do not need lifting. Annuals like the gloxinias and begonias will die out if they are not brought in prior to fall frosts.

Your Yucca plant likely did not bloom either because of too much kindness or not enough direct sunlight.

The enclosed literature will help answer your other questions: "House Plants Proper Care and Problem Solving," PP-744, and "Annual and Perennial Flower Selections for North Dakota," H-322. Others may obtain these publications from any county office of the NDSU Extension Service or by calling the State Distribution Center at NDSU, (701) 231-7882.

Q. I read your column every week. There is always something new and interesting to learn.  My question is about a begonia I have had since Mother's Day 1995. That spring and summer it was outdoors in my wishing well. That fall my daughter took some slips from it. One grew and I have had it potted and growing inside in front of my south window all this time. Up until this winter it grew and blossomed beautifully. Now it still blossoms, but they start opening and turn gray and die.  What is wrong? Is it a disease that might spread to my African Violets? Or is it something I am doing wrong?  It is in a pot with no drainage, but it is a very large one and I filled it one-third full of perlite then put the soil in.  Thank you for any help you may have for me. (Willow City, N.D.)

A. It sounds as if your plant has a fungal disease known as gray mold. This is brought on by too much moisture, overwatering, or too high a humidity—usually it is initiated by a wound of some sort.

You gave me a good hint—using perlite in the lower one-third of an undrained pot. This creates, eventually, anaerobic (oxygen-lacking) conditions in the soil, predisposing it to a disease like gray mold.

I suggest repotting in an African Violet (high organic) mix, in a freely drained pot (no perlite). Pick off and throw away any plant parts that exhibit the symptoms you described. Perhaps, in time, it will return to full heath.

Thanks for writing and the nice comments about the column.

Q. Thank you for your help before. If I get to Fargo, I hope my son can help me find you and show you a couple of plants. It seems like there are little spiders, but my vision is slipping (at 91 that happens, they say) so I can't quite know. Red spots occur and then the leaf turns yellow and dries up on the calla and several amaryllis plants. I don't water and feed the plants as well as I should. Actually, I should dispose of most of them. The Christmas cactus is 67 years old and a gift from my Mother and most plants are gifts. Have you suggestions for what to do with tuberous begonias? It's too windy here to hang them out.Thank you. We read all your comments and learn from them. (Rolette, N.D.)

A. Wow, 91 and still going strong--nice to have you around and asking questions. Calla and amaryllis need an annual rest period. Allow the foliage to dry down and the plants to stay dormant for about six weeks. Then repot, place in a sunny location and water. It appears you are fighting a natural tendency of the plant to shut down. Christmas cactus is a jungle species as well and needs to go through a wet/dry cycle with growth and need for abundant water from spring to fall. When flowering is over, allow the top part of the soil to dry before watering again. During active growth, they need a tomato-type fertilization on a regular basis.Try tuberous begonias as pot or bedding plants.Thanks for writing.

Q: I enjoyed a beautiful potted tuberous begonia all summer on a semi-shaded patio--now what do I do with it this winter so I can enjoy it again next summer? (E-mail reference, Forestburg, S.D.)

A: You might have a couple of options: allow it to dry down by watering sparingly, and when the stems wither, overwinter in a dry peat medium keeping the temperature at about 45 degrees F. (basement would be o.k.). Then in April, repot and move to a warmer location where it can get some natural, but indirect light, watering gradually. When shoots begin to appear, water more liberally, and when the plant is in full leaf, fertilize on a biweekly basis right through the blooming period. If your plant was the type that was still in flower when you brought it in, keep it in strong indirect light, allowing to have an extended rest (flowerless) period, watering enough to avoid wilting. Next spring as the days get longer, you should see some new growth and buds forming. Increase watering and fertilize.

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