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Hortiscope

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

By Ronald C. Smith, Horticulturist

NDSU Extension Service

Q: I have had creeping Jenny in my garden for two years. We sprayed with Roundup three times in 2005. We sprayed before planting and while the garden was growing. It took over the garden that year, so the only thing we were able to harvest was a few potatoes. We did not plant a garden last year and did not spray (as I gave up on it), but the creeping Jenny didn't seem as bad. I would like to have my garden again this year, but I'm afraid the creeping Jenny will take over again. What can we do this spring to get this weed under control? (e-mail reference)

A: Field bindweed (creeping Jenny) is very difficult to control because of its extensive root system. In turf situations, where cultivation is not practical, a postemergent herbicide is recommended. Small infestations of bindweed in nonturf areas sometimes may be controlled by covering the area with mulch and not allowing any green plant material to emerge. Field bindweed control is best achieved when plants are actively growing and in the seedling to flower stage of growth. Multiple applications may be required for complete eradication. The reason for it not appearing to be as bad last year is probably linked to your persistence the previous year, which weakened the energy reserves of the plant's root system. I really think your best approach is to follow a combination approach of spraying anything that comes up with Roundup and covering the area with a black tarp for this growing season to hopefully starve the plant to death!

Q: I purchased a Christmas cactus that was full of buds and flowers. After a couple weeks at home, all the buds fell off. What would cause this? (e-mail reference)

A: Moving the plant from a florist or greenhouse environment to a home environment in winter where the humidity goes from 60 percent or higher to one where the humidity is 10 percent or less will cause the flower buds to drop. Christmas cactus is a forest cactus that lives in constant high humidity. Eventually, the plants acclimate to our low home humidity settings and bloom beautifully. Be patient. Eventually, the plant will grow ample, beautiful flowers.

Q: I have read your feedback to people on the NDSU Web site for a couple of years. I appreciate the information you are willing to provide. I have a jade that almost grows too well. It rarely takes a break. I have noticed small, white dots on the leaves. The dots are no larger than a millimeter and do not seem to be spreading. The dots are located on the tops of the leaves. It doesn't seem to be scale, mealy bugs or mildew, so I really don't have a clue what else it may be. Any help you can offer in identifying the dots is appreciated. (e-mail reference)

A: Those dots are salt crystals and can be wiped off with a damp cloth or just ignored because they are not causing any harm to the plant. All water (except distilled) contains some salt. When fertilizer is added to the root system, the plant takes up the nutrient salts with the water. As the water moves through the leaf pores during transpiration, the salts often are left behind on the surface.

Q: Last fall, before the frost, I took into my sunroom a potted lily that was going to bloom. In the middle of November, I noticed that the buds were full of little, green bugs. I immediately put the lily back out into the cold and no longer cared if I ever saw the blooms again. I also noticed a few of the bugs on my hibiscus. I have been spraying Raid House and Garden spray, but can't seem to get rid of the bugs. They also have traveled to a fern. Do you have any suggestions? The bugs on the fern look more like spider mites with webs. The fronds are turning brown and dying. (e-mail reference)

A: The problem on the fern sure sounds like spider mites. To control them, you need a miticide, not an insecticide. It may be the infestation already is too far gone, so you may have to dump the plants. Your description of little, green bugs on your lily sounds like aphids, which usually are easy enough to control if caught early. Again, the infestation may be too intense, so it may not be feasible to attempt control.

Q: I enjoy your Web site! Please send me information for the propagation of Christmas and Easter cactus and information on air-layering of plants. (e-mail reference)

A: Thank you! You can download it yourself in a heartbeat at http://www.ag.ndsu.edu/pubs/plantsci/landscap/h1257.pdf.

Q: I have a question about the three cactus plants I purchased. I believe they are different types. Two of the plants are growing green roots off the top. They resemble roots on a potato, but are bright green. Is this some sort of fungus? (e-mail reference)

A: These are aerial roots and likely are from a Christmas cactus species. Go to my Web site on cactus at http://www.ext.nodak.edu/extnews/hortiscope/houseplnts/xmascctus.htm for some self-education on the species.

Q: I saw your page on the Net and am wondering if you could help me. I planted a silver maple by the house about eight years ago. I was dumb and did not pay attention to how close it was to the house. The trunk is about 80 inches around and about 10 feet from the back corner of the foundation. I have had no foundation issues, but I am wondering if I should remove this tree to avoid any issues in the future. Thanks for your help. (e-mail reference)

A: I doubt you will have any trouble with the roots. It is more likely you will have problems with branches overhanging your house. I would suggest contacting an International Society of Arboriculture-certified arborist in your community to have the tree inspected for any potential hazards. To select one in your community, go to http://www.isaarbor.com/findArborist/findarborist.aspx and follow the prompts to find those listed for your community. Be sure to check their credentials and references before allowing any work to be done on the tree.

Q: I have a dieffenbachia that was very small when purchased. Now it is growing, but it is very skinny. How do I prune the plant so it gets big and beautiful? (e-mail reference)

A: The plant needs more light. It is unlikely that you can get this plant to convert to a thick, well-muscled plant. I would suggest doing air-layering to produce a plant. To do this, go to my Web site at http://www.ag.ndsu.edu/pubs/plantsci/landscap/h1257.pdf for instructions. You can download the entire publication for free or just read the part about air-layering.

Q: We have a cotoneaster hedge that has grown too tall. Would it be advisable to trim it and take off about 12 inches or more? If so, when would be a good time to do it? Any help would be greatly appreciated. (Moorhead, Minn.)

A: The cotoneaster hedge can be trimmed any time between now and spring growth. If you want to completely renew the hedge, cut it back to the ground. It will sprout and grow back quickly. Otherwise, trim it to the height you want before new growth begins.

Q: We've had a spider plant for more than a year. It hangs in a pot in a west-facing window. Although it has grown nicely, it has never produced spiderettes. The plant appears healthy and does not have any browning at the tips. We follow your tips on watering and everything else. We use 1/4 teaspoon per gallon of Miracle-Gro in tap water with each watering. Do you have any idea why this is happening? (e-mail reference)

A: What you need is patience. The plant is becoming pot bound, so stop giving it so much fertilizer because it isn't needed. Eventually, it will start producing babies and you'll be giving them away to family and friends!

Q: Would you please tell me what can be done with a bare area of a birch tree? This is a healthy tree otherwise. The tree always had the bare area. Would you have any other advice about shaping, caring for or replanting? (Esmond, N.D.)

A: Birch trees should be pruned minimally. Sorry to say, but the condition your tree is in cannot be corrected by pruning. Basically, you have two choices. You can live with what you have or replace the tree.

Q: My wife and I have been saving gerbera daisy flower heads thinking that there were seeds in them. We have tried to plant several seeds this year, but no plants are growing after 10 days. Any help or advice would be greatly appreciated. I am starting to think that what we planted are not seeds. (e-mail reference)

A: Gerbera seeds (there are 6,000 to 8,000 seeds per ounce) are expensive, delicate and sensitive to germination conditions. Considering that the crop requires 14 to 18 weeks from seed to flower, many small- to medium-sized growers order established, plug-grown seedlings from specialist propagators. The seeds should arrive packed in moisture-proof packages. The packages should be stored under cool conditions and away from strong sunlight. Once the package is open, the seeds should be planted right away because they lose viability very quickly when exposed to room conditions. Add to this day/night temperature controls and light/dark periods, with consistent moisture under sterile conditions, and you can see why specialization exists for this crop! You are to be commended for your gallantry in attempting to grow this flower from seed. I wouldn't attempt to do it myself even though I have three degrees in horticulture! You are better off purchasing plants from competent, successful growers.

Q: I found your Web page about spider plants. I learned quite a few valuable tips and pointers. There is a question that I did not find an answer to, so hopefully you can help. My mother has had a spider plant for at least 15 years. It is beautiful, though it is not what it used to be. I remember it once had a zillion babies and was quite large. She has split it several times and given away hundreds of babies during the years. Lately, it has not produced many babies. It has, as of a week ago, only one. My mother, knowing how much I love her plant, clipped it and sent the baby to me. Her plant is still healthy, but now empty of all babies. The problem I am having is that she sent the baby to me in a Ziploc baggie, with a damp paper towel around it. It was sent with a friend, forgotten and left in the bag for about five days. When I got it, I put it in water and it has perked up a little. It is still green and not losing any color. Though it looks healthy, I have noticed little, white, rootlike things growing out of the bottom. I say rootlike because I now believe these little things are actually pods, such as you have mentioned to someone else. These little pods are fuzzy. I believe it is mold. I am afraid that my mother's plant will not produce more babies. Is there any saving this little guy? Any advice you have would be much appreciated. I am sorry my question ended up as such a long e-mail. Thank you for your very valuable time. (e-mail reference)

A: I doubt that what you are seeing is mold. It probably is root hairs coming from the root stubs or initials coming from the spiderette. If I referred to them as pods in past correspondence, I was mistaken. I suggest planting the newcomer in African violet potting soil and keeping it moist. It slowly will grow and eventually produce babies. As for your mom's plant, be patient. It too eventually will produce more spiderettes.

Q: Is there a lawn grass variety that is salt tolerant? This would be for a rural setting. The guy had his well tested and told me that the salt level was 486 milligrams per liter. The water is typical for our area because it looks like tea. What about use of this water on new trees, specifically junipers and pine trees? (e-mail reference)

A: The grass species would be Fults alkali grass. It is the most salt-tolerant species on the market. The rural water can be used, but drainage is critical and maintaining an even moisture level is important. Of course, the growth will be greatly stunted.

Q: I have a Newport plum tree that I planted about nine years ago. It has been an easy tree to care for and provides shade and beauty to my yard. However, I have been reading that plum trees planted near sidewalks can cause damage to the sidewalk. Mine is not near a sidewalk, but it was planted 10 to 15 feet from my septic tank. Could the roots of my plum tree damage my septic tank? If I have to remove it, I'll want to replace it with another shade tree. Are there any trees that have root systems that would not run deep enough to damage a septic tank and would be hardy enough for the hot summers and cold winters of the mid-Washington state area? I appreciate any help that you may give. (e-mail reference)

A: Septic tank seepage is a temptation for any tree's root system. Poplars, silver maples and willows are the worst. I suggest that you contact the county Extension agent to see if there is a horticulturist or forester who can help you make a selection that would be the least of the evils for your region of the country. You also could have a root barrier installed between your tree and the septic system. That might be the least expensive and best alternative for you.

Q: We have a hedge that lines our downtown park in Casselton. I would like to trim it next spring. A gentleman who was involved in the planting of the hedge more than 20 years ago told me that they are a variety of shrub called nannyberry. The hedge runs the length of the park. We have a difference of opinion concerning how the hedge should be maintained. In past years, we trimmed the hedge up the sides so it didn't get too bushy and interfere with our spring and summer mowing. I would like to cut the hedge down to a more manageable height of 5 or 6 feet, and maintain it there. My colleague says that type of planting is not designed to be trimmed in this manner. My guess is that it is a matter of personal taste, but I don't want to damage the hedge. Please also let me know if spring is indeed the best time to do the trimming. We plan on having some other landscape work done in the park this spring and it would be helpful if the hedge work is done prior to the landscaping. Thanks and keep up the great work with NDSU and your column. (e-mail reference)

A: Most hedges, such as cotoneaster, honeysuckle, forsythia and privet, can be pruned. This is a native plant of different characteristics. Justice couldn't be done to it by giving it a shearing the same as a hedge. To control the height and spread, trim out the oldest canes back to the base of the plant. This will help the plants retain their natural form and not give them a manicured look, which I seriously doubt they could survive. Thanks for your very kind words. They are very encouraging. I try my best.

Q: What kind of help can I give my tree that has twigs with small areas of no growth? Those areas tend not to bud. Some of the branches had black spots at the center. I pruned off those areas. I’ve continued to prune until the exposed areas look healthy. I am concerned about my tree and did not know what to use to stop this disease, if that is what is happening. I think the tree is a pink pussy willow because it has huge, fuzzy buds. (Roseburg, Ore.)

A: The best thing you can do is get the disease organism identified by someone from Oregon State University’s plant pathology department. Its Extension Service branch at the university should be able to provide that service for you and make the proper recommendations for control. You might want to check with the Extension Service office in your county to see if it has a horticulturist or plant pathologist who can advise you. Unfortunately, pussy willows are hosts to a wide range of diseases, such as stem cankers and leaf spots. You can try an all-purpose fungicide, such as Funginex, with the hope that it will stall or stop whatever is causing the problem.

Q: How do cedar and lodgepole pine grow in North Dakota? (e-mail reference)

A: Selecting the plants based on their seed ancestry is important. Lodgepole pine typically is hardy to zone 5, but with the zonal changes now being re-established, it would be bumped up to zone 4, which would incorporate a large area of North Dakota. Research indicates that seed selected from the northern provinces of Canada or higher elevations will survive better than seed selected from more southern locations or lower elevations. The same would apply to the cedars.

Q: I have African violets that are doing well, but a few leaves are losing color and becoming white. There are no insect infestations and I do not think it is a fungus or mold. This has happened once before, but it went away. I would like to find out what causes the problem because the plants are very unattractive during this period. (e-mail reference)

A: If it is not powdery mildew, then I don't know what the affliction could be. This usually is brought on by stagnant air and high humidity.

Q: I bought a tulip a few weeks ago. It flowered for few days after I purchased the plant, but then the stem bent, became dark green and eventually made the flower point toward the ground. I thought it was due to a lack of water, so I propped it up and have been keeping the soil moist. Yesterday, the flower began to wilt. Is my tulip dying or is this normal tulip behavior? Can I save the tulip bulb if I cut the flower off and wait until the leaves turn yellow? (e-mail reference)

A: In a nutshell, the answer is yes! The bulb can be planted outdoors this summer and will or should produce some flowers for you the next spring.

Q: I would like to know what time of year peonies start to bloom and how long into summer they bloom. Do they bloom up to the first frost? (Berryville, Ark.)

A: You need to educate yourself on peonies. Go to my Web site at http://www.ext.nodak.edu/extnews/hortiscope/flowers/peony.htm for the information. The information is valid for North Dakota and the surrounding areas of the upper Midwest. What they do in your part of the country would be a guess on my part. I imagine the same pattern would follow, but not the same months. I doubt that the peonies will flower right up to the first frost. You might want to check with the horticulturists at the Arkansas Extension Service through your county office or the university.


NDSU Agriculture Communication

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