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Published June 25, 2010, 12:00 AM

Additional soil may hinder oak tree growth

Q: I am in a panic trying to figure out how to save a big oak tree in my yard. I believe it is a burr oak. Two years ago, I did some dirt work in the yard around the tree and increased the dirt level above the roots by about 6 inches.

By: Don Kinzler, INFORUM

Q: I am in a panic trying to figure out how to save a big oak tree in my yard. I believe it is a burr oak. Two years ago, I did some dirt work in the yard around the tree and increased the dirt level above the roots by about 6 inches. From what I have read, it was too much additional soil. The tree looked good last year, but not so good this year. The tree was full of buds earlier this spring and leaves started coming out, but they have stopped. All the leaves are there but they only are 1 inch long. It’s like the tree put itself on pause. Would it help if I tilled the ground above the roots and removed some of the dirt? Would it help to bore some holes in the ground around the tree to help get oxygen below the surface? (Denison, Texas)

A: I can’t tell if it is too late to save your tree. I suggest that you read through this website at http://www.treesaregood.com/treecare/treatment_construction.aspx for information on how to save the tree. Good luck.


Q: I was wondering if I could transplant my yellow raspberries into a garden that has been growing vegetables, onions, peppers and tomatoes in the past. Is it possible to change the soil to an appropriate mixture in order to make this transition? (e-mail reference)

A: Raspberries will grow where you want them. I have raspberries growing adjacent to my vegetable garden and constantly am digging up volunteers. So my “yes” answer should please you. However, I’m assuming you did not have any disease problems at the vegetable site and that it is in full sun.


Q: Our two honeycrisp apple trees have not produced any fruit. This will be the fifth year since planting them. Our neighbors have a haralson and a crab apple tree about 100 feet from our trees. We have not fertilized our trees in three years and do minimal pruning. Do you have any suggestions as to what we should be doing? (e-mail reference)

A: The trees are enjoying a vegetative life, so they need to be shocked out of their bliss. Take a straightedge spade and drive it into the soil in six or seven spots around the drip line of the tree. This will reduce some of the root volume and cause the tree to go into a reproductive cycle next year. After that, they should be a regular producer of very delicious apples.


Q: I recently purchased an old fashioned snowball bush that was labeled as a viburnum. I was thinking it was a viburnum opulus I was buying. With more research, I have a feeling that I have been mislead to think they were one and the same. What is the difference between the two and what is the correct Latin name for the old fashioned snowball bush? Are the berries edible? (e-mail reference)

A: The term snowball and hydrangea often are used interchangeably. They do not have any berries on them, just large corymbs of poufy, white flowers in most cases. If you live anywhere in the upper Midwest, the Annabelle is one of the more common bushes on the market and is as tough as a crowbar. The viburnum opulus often is termed a snowball bush that produces berries that are edible to the wildlife but not much so for the human population. For edible viburnums, consider the blackhaw (V. prunifolium) or the nannyberry (V. lentago). Both are used in making preserves and some claim they make a decent wine. These never are called snowball viburnums.


Q: I happened upon your website for information about hollyhocks. However, my question wasn’t quite answered. I live in zone 7. Last spring, I planted six hollyhock plants. They were sold as perennials and sold in quart containers. We had a lot of rain, so the plants never bloomed and barely grew. This spring, everything I planted from before is now growing and blooming except the hollyhocks. Could you please let me know if they are hopeless or if I just need to be patient? (Rhode Island)

A: There are perennial, biennial and annual hollyhocks. Typically, they are biennials, which means they are vegetative the first year, flower the second year and then die. However, they easily reseed and often give the impression of being a perennial. In your area, they should be perennial in nature. They should come back from the crown every year and have lots of volunteers around them. If your plants have not shown any life by now, I doubt that they will be coming back. Give them another 10 days because I don’t know your weather conditions.

They just might need that little extra time.


Q: I plant dahlias every year. After they were in full bloom this year, I noticed holes in the leaves that got worse every day. The people at the greenhouse told me slugs were eating the leaves. Their suggestion was to put out beer. I did that but didn’t catch one slug. Any suggestions? (e-mail reference)

A: Get some diatomaceous earth and work it in and around your planting site.

After you get the dahlias planted, put at least a 3-inch ring of the diatomaceous earth surrounding each of the plants. If it is a slug problem, this will stop them dead in their tracks! If not, then there is another critter that is feasting on your plants. They can be taken care of using the right insecticide.


Q: I have a mock orange shrub that gets plenty of sunlight. However, the leaves are yellow. What do I need to do to correct this problem? (e-mail reference)

A: Mock orange is subject to iron chlorosis in high pH soils or from being in soil that is poorly draining and kept too wet. In some instances, it could be too much direct sunlight. Sorry to say, finding a beautiful mock orange shrub is like looking for a frog that will turn into Prince Charming when kissed. If it is ever found, it is most likely a fairy tale. These poor shrubs never should be marketed because the purchaser has a set of expectations that are seldom fulfilled.


Q: The city is telling us it is planning on planting a silver linden tree on our boulevard. Are there any faults to having this tree in a small street and neighborhood? What diseases do these trees get and how old are they when these diseases begin to possibly show? What insects tend to hover around them? I ask this because there are a few people on my block who are allergic to bees. Is there any advice you would give us when having this tree planted in our front yard? (e-mail reference)

A: The silver linden would have the same afflictions as the American and little leaf lindens. These problems include Japanese beetles, aphids, basswood leaf miners, thrips, elm sawflies, leaf blight, stem canker, powdery mildew and verticillium wilt, to name just a few. Bees love the linden flowers, but this one supposedly is toxic to bees, according to reports in German literature. This is something I hope the city would check out before going wholesale in planting this tree. Otherwise, they are a decent tree.


Q: Our neighbor has an old cottonwood in his backyard that is very tall. It was planted about 10 feet from our property line. The tree has two huge, dying limbs that are hanging over our backyard and house. The tree is very old and has not been pruned or groomed in years. I would guess that it has been there since the neighborhood homes were built in the 1920s. We had two tree services look at it this year. Both said the tree is at the end of its lifespan. They also said the tree has areas of rot in one of its two main trunks and that it poses an imminent risk of damage to our home. Also, our gutters are continually clogged with debris and the tree’s roots reach the sump well in our basement. We have been negotiating with our neighbor for more than two years to get the two huge limbs cut back to the property line. We have offered to pay part of that cost.

On one day, he will say he has made arrangements to trim the tree the following week, but the next day he’ll report that he’s decided not to. At any rate, the big argument that our neighbor uses to dispute the fact that the tree is in dire need of trimming is that the tree can drink up to 800 gallons of water a day and that he and we will have more problems with basement water if the tree is trimmed or removed. Does his claim have any validity? (e-mail reference)

A: He is right. However, that is no excuse for not removing a tree that is a threat to both properties. A replanting of a less ominous species, such a weeping willow, would replace the water uptake the cottonwood is providing. He could plant one in his yard and one in your yard. In a couple of years, the higher leaf surface area would exceed any water removal an aging cottonwood would be able to provide. You might ask him how a lawsuit for negligence, when advised to have the tree removed due to a potential hazard, sounds to him. No one likes having lawyers involved, but if it takes that kind of threat to keep the tree from crashing into either or both of your homes, then so be it. I would suggest that you get written statements from the tree companies that have seen the tree. If you have a lawyer friend that could write a slightly informative letter about the consequences of not paying attention to these warnings, I think you might get some action. This tree is well beyond its normal range of life and so it is surviving on borrowed time. Take plenty of pictures from several angles to show the threat the tree is making on your properties and provide them to your lawyer. Lawsuits result in very little satisfaction, except to the lawyer, if the property is damaged or bodily harm is experienced. I hope you can get this settled amicably. One last bit of advice: Not everyone is really an expert at large tree removal. Be sure to check the credentials of the company or individual you are intending to hire and make sure the person or company is insured for any property damage that may occur. Finally, I don’t advise either you or your neighbor staying in your houses while the tree is being removed.

Falling trees have crashed through houses and killed the occupants, so don’t be there!


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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