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Hortiscope

Ron Smith answers reader's questions about the world of plants and gardens.

By Ron Smith, Horticulturist

NDSU Extension Service

Q: I have a very old jade plant. It has grown beautifully and without problems. However, it has started dropping its leaves. How can I save this plant? It has been in the same spot for years, but was repotted three years ago. If it was a case of overzealous watering, will it recover if left to dry? Should I cut it back? (e-mail reference)

A: Something has changed that is causing this response. It could be overwatering or the soil has compacted to a point that it is now anaerobic (lacking air). Other possibilities are light intensity or duration or temperature changes in the air or root zone from using cold water. When the central heating system kicks on in the fall, it dries the air, so the plant attempts to go into dormancy by dropping some leaves. It sounds to me like your plant is suffering a bit from not having enough of the right light, which has led to the plant having weak aerial growth and your watering regime being at a level that would require high light intensity. Allow the plant to dry down, but I also would encourage you to get more light on the foliage. The plant should get light at least 12 hours a day.

Q: Even though it is the middle of November, I’m still enjoying spinach from my garden. What are my chances of growing spinach using indoor light during the winter? (e-mail reference)

A: From good to excellent! Use sterile or pasteurized media, don't keep the room too warm and provide some gentle air circulation around the plants. We still are enjoying a harvest of carrots from our garden, too. For taste, they beat the daylights out of what one can get in the supermarket. Nothing like fresh carrots for flavor! Enjoy the good health benefits of your own spinach crop!

Q: I have a tree that has part of a root growing above ground and part of the bark on the trunk has broken off. Will the tree live? Is there anything I can put on it to help it survive? (Alberta, Canada)

A: If the tree will live or die is not a prediction I can make with the information you have provided. Generally, trees in good health should be able to shrug off the damage that you described. If there is any loose bark where the damage to the trunk was done, you might want to take a knife and cut back to where it is attached. That will speed up the healing when spring arrives. You don’t need to use a wound dressing or anything else.

Q: Our hibiscus plant will be left outside for the winter. Should the plant be cut back? If so, how much of the stem should I leave? (Pawley’s Island, S.C.)

A: First, make sure the plant is dormant. Then cut it back about two-thirds the length of the plant. I’m assuming your soil doesn't freeze during the winter. I would cover the lower stem with mulch in case of sudden, extreme freezes.

Q: I'm in desperate need of help with my Christmas cactus. I think I damaged the roots when I repotted it a couple of days ago. Its branches are becoming limp and dropping off. I cut into the roots in several places to loosen the roots and dirt because it was so tightly wound. The roots looked a bit rusty. I love my plant, so can you suggest anything else I can do to save it? (e-mail reference)

A: I have a few ideas you may want to consider. Keep the roots moist. Take some leaf cuttings and root them in a sand/peat mix in an attempt to extend the plant into a new generation of flowering. You also might try to mimic the plant’s native setting by placing a clear plastic bag over the plant to see if that cuts down on the wilting response.

Q: My plant is about 20 years old and has lived indoors, except the past two summers. I have had very little bloom until I put it outside. I bring it indoors during late September. It comes into the house filled with buds, which does not make sense because it is on a south and west-facing porch. I have hundreds of flowers on the plant now. But why does it bud on the porch instead of waiting for the dark/light treatment? When is it best to trim it back? (e-mail reference)

A: I can't give you a valid reason why the plant is blooming under those conditions, except to say that something else stimulated the production of the flowering hormone. The blooming is something for researchers to investigate. The best time to trim is after flowering.

Q: Can you please help? I intend to put zinnias down the front of a wrought iron fence that I’m having installed. Should I start them indoors or should I sprinkle seeds in the bed where they will be planted when the snow is gone? (e-mail reference)

A: You can sow the seeds directly or purchase plants, which, in my opinion, will give you better results.

Q: We have a blue spruce here in Indiana that is 20 to 25 years old. It is a beautiful tree, but it blocks our view! We would like to take off the bottom six to eight limbs. How and when should we do this? (e-mail reference)

A: Cut the limbs back to the trunk next spring after the frost leaves the ground. Use a pruning saw to make a clean cut.

Q: I am so thrilled to have found you! Seedlings are coming up for two varieties of cherry tomatoes that I hope to grow indoors this winter. Do you suggest that I get the fluorescent lights you spoke of in answering one of your questions? Is there a place I can get the lights in a unit that is already assembled? Should I get a portable greenhouse for my home to grow the tomatoes? If this works, I would be interested in finding out how I can make a business out of growing tomatoes indoors. (Hartford, Conn.)

A: Thanks for telling me where you live! Most people don't bother to let me know where they live, but still expect that I give them sound answers to their questions. Without a doubt, you need to get some light on the tomatoes. You can purchase a plant light as a total unit. These can be found in just about any major store. A portable greenhouse sounds like a little overkill to me! I hope this answers all of your questions and wish you all the best!

Q: I purchased six sweet viburnum plants to fill some empty slots in my front lawn. In less than a year, the leaves wilted and turned brown. I'm not familiar with this type of disease, so I contacted a department store with a gardening center. The person at the store told me to use a product to help eliminate rust. After I used the product, the leaves practically all fell off. Please explain to me what happened. (e-mail reference)

A: Here is what I think may have happened. I believe you probably live in central Florida and have an automatic irrigation system. The spray from the irrigation system impacts the foliage. This may have created an environment hospitable to disease development, such as a leaf fungus or bacteria, that caused the defoliation. I don't know what you were given by the retailer, but it obviously wasn't the answer. If I am wrong in this assumption, then the plants probably were located in an environment that did not lend itself to foliage drying, so the high humidity kept the leaves receptive to disease development. The shrubs also may have been planted too deeply.

Q: I enjoyed reading your e-mails about spider plants. I have a large plant that is doing very well. When I bought it, the babies were sticking out at an angle, so it looked like a whirling dervish. As it got bigger, the babies gave up this nice habit and now hang straight down. If I trim a few babies off, will the new babies grow at an angle again? (e-mail reference)

A: At one time in our lives, we all were whirling dervishes. Now we are lucky to be able to get up, walk, dance or run a few steps! In my experience with these plants for more than two decades, that seems to be their characteristic. It might have to do with the amount of light energy reaching the plants, but I don't know for sure. When I have seen some spider plants growing in the South where there is more and greater light, they seem to have that energetic appearance you describe. Growing indoors in the North, not so, unless supplemental light is provided.

Q: I have a spider plant that has been very healthy and produced lots of babies. Now the leaves are turning limp and yellow. Could this mean the plant has become pot-bound? I have it in a ceramic pot that does not drain. Do I need to place it in a drainable pot? (e-mail reference)

A: You have identified the problem. Keeping the plant in a pot that doesn’t drain is bad news. Anaerobic conditions develop in the root area, so the plant slowly dies. Get the plant repotted in something that drains and put a 2- to 3-inch layer of stone or gravel on the bottom and place the spider plant on top of that. Being pot-bound is not a bad thing for spider plants because it seems to force them to become more productive, which everyone seems to want.

Q: I have a double delight rosebush and a pink grootendorst bush. Last year, I covered the roots with dirt and the bushes came back nicely. This year, the bushes are very green, even though parts have frozen. I am not sure if I should cut them back or just pile dirt around the root area. (Aberdeen, S.D.)

A: Thanks for letting me know where you live. My best guess would be to have the soil ready to pile up around the plants if it looks like a winter clipper is going to close everything down for the season. My concern is with your statement that everything is still green. If you can wait for another freeze or two before cutting and covering the plants to be sure they are dormant, that would be good. Cut the stems back about two-thirds of their length and cover as much of the plant as possible with pasteurized potting soil or topsoil.

Q: I gave my wife a little plant a few years before we were married. We called it our love fern, although it is definitely not a fern. We now have been married 32 years, so the plant is huge. It is a tropical plant of some kind. It is the same type of plant you see all over Disney World. It has large, dark green, symmetrical leaves. The leaves are not smooth at the edge. Our plant has developed three distinct trunks. We live in Michigan and the plant stays outside during the summer months and loves it by adding new leaves and growth. I built a dolly for it, so we roll it in the house in the fall and roll it back out in the spring. We have two problems. The plant is so big that it takes up a large portion of our living room. Also, the plant is root-bound and has outgrown its pot. We would like to try to split the plant in three so we can give one to each of our children, but we have no idea how to go about it. Can you give us any help? (e-mail reference)

A: I'm guessing this is a palm species. They can be divided and given to your family as keepsakes. This would be a monumental task to complete for someone who is not inclined to do that kind of work, so I would suggest contacting a local flower shop or nursery for help. I would assume that you would purchase the potting soil and new containers from the shop or nursery, so the price shouldn't be exorbitant. Congratulations on 32 years of marriage! My wife and I are coming up on 31 years of marriage. How time flies!

Q: I've been reading some of your random houseplant advice. It sounds really solid, so I thought I would ask you about mold that seems to be killing a couple of my plants. My wife and I have about 40 plants in our one-bedroom apartment. We have mold inside the walls from years of a leaky roof. The mold never appears on the walls, but it seems to like some of our plants. Some plants, such as our burgundy ficus, are good at fighting off the mold. It will appear on the undersides of the leaves and around any injured areas. When we wipe it off with a wet cloth, it doesn't come back. Other plants have more difficulty. We've had to give away a few vine plants. Once the plants have moved to their new home, the mold goes away. We have a couple of palm-type plants. The mold has attached itself to the leaves, which causes the leaves to become pale, then brown. Eventually, the leaves die. We want to keep these plants, but we can't seem to keep the mold down. The mold is grey and fuzzy. When I wipe it off with my finger, it's slightly sticky. There's also some bright green stuff on top of some of the soil, but it doesn't seem to affect the plants. What can we do? Thanks in advance for your help! (e-mail reference)

A: Let the mold on the plants be a “miner's canary” to you and your wife! You have an indoor air quality problem that could have negative impacts on your health. Insist that the leaky roof get fixed and do something to reduce the humidity in your living quarters as well. I would get a small fan to keep the air moving. All of these steps will reduce the mold on the leaves, soil surface and walls of your apartment.

Q: I have been reading through your Web site in hopes of finding help for my jade tree. It is more than 30 years old. The plant was given to me by my mother last year because she is moving, but she would like it back. It adjusted to the new living quarters fairly well, though I did have a problem with mold on the soil and then the leaves falling off. I adjusted the frequency of watering, so the leaves stopped falling off and the mold went away. However, I found a large broken branch. The stump was rotten, although the leaves at the top of the branch are very healthy and showing new growth. I cut the stump as close to the soil as I could, but there still is a rotten piece of stump at the soil level. I am afraid that the rot will spread to the neighboring branch or to the roots. Is there a way to remove the damaged stump without killing the root system? This plant is very important to my mother, so I want to save it if possible. I did trim the broken branch in hopes that I can get it to root. It has survived rot problems before. I remember large branches falling off when I was a kid. Is there any hope? Do you have any suggestions for removing the stump below the surface of the soil? (e-mail reference)

A: How are you with a knife doing careful (surgical) cuts? If you feel confident enough, go for it. Cut below the soil line to remove the rotted part. This rotting indicates that the soil probably is not draining very well. If you have the courage, repot. If not, try to keep the plant alive until your mother takes it back and let the problem be hers!

Q: I treated my sewer line with copper sulfate this spring, but I forgot to do it this fall. Will the copper sulfate do anything if I use it now or do the trees need to be growing? Does it kill the roots by contact? At $6 per pound, I don't want to waste it. My line is 400 feet long with a cleanout in the middle. I put 2 pounds down my basement toilet and 2 pounds down the midway cleanout. (e-mail reference)

A: The roots are actively growing in early November. Most of the growth is during fall, followed by a spring growth surge. In trace amounts, the copper sulfate solution is absorbed for a limited distance into the roots. It then travels up and through the vascular system of the plant in high concentrations. After the copper sulfate is absorbed, the root is killed in that vicinity, usually going back a few inches at most. At that point, the root develops a new growing tip and will re-enter the break in the pipe, so an annual application is needed. I also am told that regularly pouring small amounts into the sewer line is better than dumping in large doses. If there is such a company in your town, have it come out with a camera that can be put into the line to find out where the roots are intruding. With the right sophisticated equipment, it then can be determined where and how deep that intrusion is. Using a soil auger, you can go deep enough to find the intruding root, cut it out and saturate the soil with your copper sulfate. This will keep the roots from penetrating for several years. Copper-infused burlap has been shown to prevent root penetration and some pipes have a copper lining to keep the roots from damaging the pipe.


NDSU Agriculture Communication

Source:Ron Smith, (701) 231-8161, ronald.smith@ndsu.edu
Editor:Rich Mattern, (701) 231-6136, richard.mattern@ndsu.edu
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