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Published March 04, 2011, 12:00 AM

Hortiscope: Have ailing cottonwoods pruned by arborist

Q: We live on Fox Island in Bismarck and have many cottonwoods in our yard. This winter, we are seeing something we have never seen before in the 16 years we have lived here.

By: Don Kinzler, INFORUM

Q: We live on Fox Island in Bismarck and have many cottonwoods in our yard. This winter, we are seeing something we have never seen before in the 16 years we have lived here. The trees are dropping many branches that have what appear to be green buds on them. They are not broken off from the wind because they fall in great numbers on still days. It looks like healthy wood at the base where they separated from the tree. Any idea what might be going on? (e-mail reference)

A: This phenomenon is something that has been studied worldwide. While there is no direct biological cause that can be nailed down, it has been found to be associated with particular tree species in advanced stages of maturity. The trees with the problem are usually more than 16 years old. There is no disease or insect problem associated with this problem, so there is nothing to spray.

The current recommendation is to get the trees pruned by a professional arborist. We had this problem with some of our mature poplars on campus the past few years. It became a hazard to mow under these trees. After investing in a major cleanup and balanced pruning by a local professional, the problem appears to have abated. The best advice I can give you is to have a certified arborist in your community do some selective pruning. Have it done as soon as possible.


Q: I have a large maple in my front yard. During the past few months, bark has been falling off the upper branches. I’m not certain what the cause is. From what I have read, it might be some type of canker. I do have some squirrels, but I’m not sure they could be doing that much damage. Can you help me figure out what the problem is? (New Jersey)

A: I cannot tell for sure what the problem might be. However, never underestimate the destruction squirrels can cause once they get started. I strongly encourage you to contact a certified arborist in your area. To find one, go to www.treesaregood.com/findtreeservices/FindTreeCareService.aspx. Be sure to check his or her credentials and insurance before allowing any major work to begin.


Q: I pruned my jade plant a week ago and am using some of the cuttings to grow new plants. I have four stems and eight leaves sticking in some soil or laying on top. I water them every two days with a spray. Am I doing the right thing? (e-mail reference)

A: Basically, you are doing the right thing. To get more details on plant propagation, go to my publication on the subject. You can download it by going to www.ag.ndsu.edu/pubs/plantsci/landscap/h1257.pdf. I assume you’ve read the section on the website concerning jade culture and problems. If not, give it a visit at www.ext.nodak.edu/extnews/hortiscope/houseplnts/jade.htm.

Good luck and thanks for writing. The most important thing for you to practice right now is monitoring and patience.


Q: I have been growing hazelnuts for about 25 years. I found it interesting that you had an article about them in your Hortiscope column. I also have ordered from St. Lawrence Nursery and found the nursery to be an ­excellent choice. I also have ordered from Badgersett Research Farms. The people at Badgersett gave me a great deal of help with learning how to grow hazelnuts (www.badgersett.com). There are wild hazelnuts growing in North Dakota and Minnesota that can be crossed with nursery varieties to give the grower a better crop. However, some wild hazelnuts carry eastern filbert blight. The blight has not affected the trees from the St. Lawrence Nursery or Badgersett Farms. The blight has affected my second- and third-generation plants and some wild varieties that I have grown. The other problems are deer in the winter and squirrels in the fall. The hazelnut trees seem to be able to handle drought, floods and grass after they are established. They have no taproot but do have plenty of surface roots, so take it easy on the tilling. The hazelnuts on my property are growing in a heavy clay soil with a high pH. They grow in full sun but also will do well with some shade. The easiest way to grow them is to plant the nuts in the garden in the fall and cover them with a heavy rock or board so squirrels can’t dig them up. Move them in June to their permanent locations after they come up. (e-mail reference)

A: Thank you for the information! I will pass this information on to Hortiscope readers. I was unaware of the filbert blight, so thanks for that information.

Lacking a taproot would make them easy to transplant in the spring. I also checked out the Badgersett Farms website you suggested and found it to be full of excellent information. I like the use of the term “wood agriculture.” It is a term I had not heard before. Thanks again.


Q: My Norfolk pine plant is getting large. Is it OK to cut back all of the branches to narrow it down? It takes up a lot of space even though I keep it in a corner of the room. (e-mail reference)

A: As much as I hate to advise such treatment, you can go ahead and prune it to better fit your room. Give each pruning cut a lot of thought because a branch is gone forever when it is removed. Cutting back to a bare part of the branch will not generate new growth, so you might as well remove it entirely. Cutting into leafy tissue may result in a new bud set at that point. However, I cannot say that for certain because a home environment is far different from a native setting.


Q: I have seeds from some grapes that are very hardy and produce every year. Do I need to do anything special with these seeds to get them to germinate? Should I do a cold treatment or something else? When should I plant them? (e-mail reference)

A: Let me try to discourage you from attempting to get grape seeds to germinate.

Grape seeds have a lot of dormancy to overcome. The seeds would need to be refrigerated for 90-plus days followed by a warm period. Next, the seeds would need a hydrogen peroxide treatment followed by something else that I can’t recall right now. If your objective is to get some grapes to grow in your yard, take cuttings and stick them in the ground this spring before they leaf out. You also could take cuttings now for indoor planting and then plant them outside this spring after the threat of frost has passed. Unless you are a breeder attempting to create hybrids, you have no real reason to try germinating grape seeds because it is easy to propagate them asexually from cuttings.


Q: I read a magazine that listed trees that do well in North Dakota. However, I no longer have that publication. Would you be able to direct me to another? I have a friend who purchased a home in Kulm and is looking to plant trees in the yard. (e-mail reference)

A: There are a several options for you. A listing of publications dealing with trees and shrubs is available at www.ag.ndsu.edu/pubs/trees.html. Another option is the “North Dakota Tree Handbook” available at www.ag.ndsu.edu/trees/handbook.htm. You can go through a selection of trees and download the information you wish for a particular tree. In addition, you can order “Trees and Shrubs for Northern Great Plains Landscapes” from the NDSU Distribution Center. The informative book sells for $12.50, which includes postage. To order the book, send a check or money order to the NDSU Ag Communication Distribution Center, Dept. 7070,10 Morrill Hall, P.O. Box 6050, Fargo, ND 58108-6050.


Q: I have a sizable backyard with a newly installed pool. I do have a privacy fence installed. However, my backyard is adjacent to a very busy street. I would like to plant a solid line of pyramidal arborvitaes across the entire back of the yard and along one side. The idea is to get better privacy and some noise suppression. I have thought of planting some sort of maple trees just in front of this line to provide additional noise suppression and shade. Is this a sound idea? How far apart should I plant the arborvitaes? I’m thinking 3 to 4 feet apart. Once they reach a height of 6 to 8 feet, I thought I could top them and maintain them much like a large hedge. I thought I could place the maples 15 to 20 feet apart. Is this too close? (St. Paul)

A: Your thinking appears to be sound. A 3- to 4-foot spacing for the arborvitaes will give you excellent screening privacy. Scout out the details of the maples that you want because they are quite variable in rate of growth and form. Shop the local nurseries and garden centers to get good cultural advice and a wide selection of choices that will do well in your area. With these ideas in mind, I’m sure you are chomping at the bit for winter to disappear so that these chores can be taken care of and you can enjoy your new pool in luxurious privacy and comfort.


Q: We have rabbits that have destroyed the grass in our yard. Our dogs lie in the dead grass and then get worms. We read about using Irish Spring soap shavings around the perimeter of our grass. Would it help? What about Plantskydd? We would appreciate any advice you have. (e-mail reference)

A: It sounds pretty amazing to me that rabbits would be that intrusive. Are you sure rabbits are to blame? We have bunny battles all the time with gardens and fruit trees being their targets of desire, but I’ve never heard of rabbits wiping out a lawn. I doubt the remedies you are thinking about trying will work.

Such products usually deter rabbits from feeding on a plant. I don’t think they could be depended upon to repel rabbits from your entire yard. Any chance you can put up a temporary exclusion fence? Have you tried trapping them in a live trap? Rabbits aren’t very bright, so they are easily tempted by food in a trap.

Once trapped, you can do whatever you wish with them. If this is not something you want to try, then give your Irish Spring soap or Plantskydd a shot. If it works, let me know and I will pass it on to Hortiscope readers.


Q: I noticed after the snow started last fall that my newly planted American lindens were being nibbled on. The rabbits went crazy for the nice buds that had developed. Some of the trees had new branches nibbled down and some of the bark stripped off. I didn’t trust any spray to keep them away, so I put up fencing around each tree. It worked to keep the rabbits out but now I’m wondering what to expect this spring. Where the buds have been eaten off, will those nodes bud again or just hope that the rest of the uneaten buds can carry the tree forward?

I’ve had a few that almost all the buds where eaten off. Will those trees make it? I’m hopeful on the few that had bark stripped off because it isn’t all the way around the girth of the trees. I’ve read that rabbits like dogwood trees, but they barely touched those. (e-mail reference)

A: I wouldn’t give up on them just yet. Depending on how good a start your trees got last year and how much energy has been stored in the roots and crown, you might be surprised by the vigorous regrowth that could take place this spring.

We planted an apple tree in 1985 after moving back here. We were warned about rabbit activity causing problems, so we dutifully wrapped the tree with hardware cloth for protection. Unfortunately, the snow got higher than the protection, so the rabbits walked across the snow and ate the top of the tree down to the protected area. I was ready to rip the tree out the following spring, but my wife suggested that I leave it alone to see what would happen. I did, and the resulting growth created a nice, compact tree that bore apples by the bushel for many years.


Q: I read with interest your comments on hazelnut shrubs in your weekly column.

I would like to plant a few to be grown as groomed trees (cutting off the suckers). I am thinking of planting a grouping of three or four. If I do that, how far apart should I plant them? Is 10 feet from trunk to trunk sufficient or should I stay at 20 feet? Also, will elderberry, gooseberry and montmorency cherry trees survive in the Bismarck area? I have several other berry-producing shrubs that are doing well. Thank you so much for your time. (e-mail reference)

A: It all depends on what you want. Do you want a solid wall of hazelnut shrubs or a little space between them? The Corylus avellana suckers heavily from the extensive root system it produces, so a wall of hazelnut growth may fill in any spacing you choose. Elderberry and gooseberry can make it in the milder parts of the state and in protected microclimates elsewhere. As for the montmorency cherry, I wish it could be grown dependably in our area. However, I’m afraid our winters are too severe for them to give you dependable growth and production. If you want to experiment, try a couple of trees. You would need to provide protection against winter’s extremes. I’d love to have you tell me in a few years that you harvested a crop and were sending me a sample.


Q: I have a 10-year-old Minnesota gold that produces great apples. Last fall, it had plenty of smaller, good apples. During the winter, I would say a full one- third of the tree has turned black. I believe it’s some sort of fungus. What should I do? (e-mail reference)

A: Find out what is causing it to turn black by sending a sample to the University of Minnesota Plant Diagnostic Lab at 495 Borlaug Hall, 1991 Upper Buford Circle, St. Paul MN 55108.

You also can contact the NDSU Diagnostic Lab at www.ag.ndsu.nodak.edu/diaglab/. Get it done soon so that any remedial action can be carried out as soon as possible.


Q: We have a jade plant that we’ve had for a long time and has grown very large.

About a year ago, my wife and I began having itchy skin when we were in the same room as the jade. After leaving the room, the itching subsided. Can the jade plant be causing this skin condition? (e-mail reference)

A: I’m not a dermatologist and don’t want to be. However, I doubt that after this much time owning this plant that you would suddenly get such a reaction.

However, anything is possible! I would suspect that it might be mites causing the itching. I would encourage you to visit a dermatologist. Take along a sample of this beautiful-sounding plant so tests can be run to see what is going on. If it turns out you are suddenly allergic to the plant, I hope you can find a suitable home for it. I know there are many people who would love to have a large jade plant in their home.


To contact Ron Smith for answers to your questions, write to Ron Smith, NDSU Department of Plant Sciences, Dept. 7670, Box 6050, Fargo, ND 58108-6050 or e-mail ronald.smith@ndsu.edu.

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