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By Ron Smith, Horticulturist

NDSU Extension Service

Q: All the tall canes in my raspberry patch died this spring. I think it was because of the mild winter and then a late freeze. All of them now are growing from the bottom. Each of the plants has three or four canes. Should I thin them out? I live in south-central South Dakota. The patch is quite thick because I don't have them growing in a row. Will I get a crop this year? (email reference)

A: Cut out the thin, pencil-sized canes. This will allow for more space and energy to be put into the stronger, stouter canes. As far as fruiting goes this year, that depends on the raspberry. If they are spring/summer bearing, they should have flowers or small fruits developing on them right now. If they are fall-bearing, they likely will bear sometime in August or September, but it depends on your climatic conditions. It likely was the winter weather conditions that killed off the canes.

Q: Our peony of 20 years never came up this year. We fertilize with 10-10-10 about every four months and water when needed. We live in southeastern Michigan. What could have happened to our plant, and how do we protect our other plants? Thank you for any information you can give us. (email reference)

A: It is hard to say what happened to your peony. My best guess is that little or no snow cover, along with rising and then falling temperatures in late February or March, killed the plant. Well-established peonies usually will outlive the property owner several times over.

Q: I have a somewhat scientific question about cottonwood trees. What triggers the tree to release its seeds? It seems as though the trees release a ton of seeds at once, rather than a slow, continuous stream. This leads me to believe that the release is triggered. I haven’t been able to pin down a time of day, temperature or amount of daylight that seems to be a trigger. Any ideas? (email reference)

A: A long time ago, as a graduate student, I could have given you a better answer than I am going to be able to do today. I’ve forgotten too much stuff through the years to be able to hit the nail on the head in answering your question. It all boils down to timing. About two months after cottonwood trees bloom, the fluffy seeds release into the wind for dispersal across the landscape. The progressive release of seeds into the air can last as long as eight weeks on each tree. Flowering time and release of seeds can vary among female trees. This means that if multiple trees exist in a grove, they may not bloom and cast seeds at the same time. In the northern part of its natural range, cottonwood trees drop seeds from June through mid-July. Farther south, it is from May to mid-July. The timing is dependent on the accumulation of sufficient hormonal levels to get the seeds to the perfect stage of ripeness so they are capable of germination upon landing at their final destination. It’s all about the survival of the species. Of course, there would be no cotton if there were no male trees around to disperse the pollen. Again, timing is important and can vary from year to year, depending on the shifting weather of our seasons. If the pollen is teased into ripening but then gets zapped by a sudden cold snap, no fertilization would occur and there would be little to no cotton. This is as good of an answer as I can come up with at this point. If someone reads this and can make an additional contribution to the answer, I’d welcome it and pass it on to you.

Q: I live in the beautiful Annapolis Valley of Nova Scotia. My neighbor has a huge maple on his lot that sits between our homes. I believe the tree was planted in 1947 and I think it may be a silver maple. This year, the helicopters are very prolific. It is the most helicopters we have seen in the 10 years we have lived here. Is this an unusual occurrence? (email reference)

A: When trees have a particularly fruitful season, it often is followed by very light to no seed (or fruit) production the following year. Sometimes, it is a signal the tree is under stress and is attempting to perpetuate the species with heavy seed production. A tree as old as this one should be inspected for possible damage that may be a threat to the surrounding properties. Corrective action can be initiated to keep that from happening.

Q: We have two aspen trees with roots that are invading my rose garden. We have installed a barrier that is 30 inches deep between the roses and trees. We also are digging out the roots. After cutting the roots behind the barrier, how large a root cut from its source will we need to remove? We are removing all we can find going down 30 inches and farther if we find more roots. We have dug up the roses and potted them to be replanted after the area is ready. Any information would be welcome. I wish we never had planted the aspens in our yard. We have three more in another area. Thank you for any help you can give us. (email reference)

A: I’m with you on the aspen roots. I made the same mistake 25 years ago. At that time, I wanted a couple of nice, fast-growing trees in my backyard. As the years passed, we dug out more and more of the tree roots until it got to the point where the trees were not appreciated for what shade or artistic beauty they contributed to our property, so out they came. It took us at least another two years to get rid of the residual roots in the garden plot. I would suggest cutting any roots you come across, no matter what the size. Also, I would encourage you to consider removing the more obnoxious trees because you’ll likely find suckers coming from the roots all over your yard.

Q: My cottonwood tree is going on three years old. The roots do not want to grow into the ground. I have had posts and wire to hold up the tree for all three years because the trunk of the tree moves around. What can I do? (email reference)

A: The first mistake was overstaking the tree. Go to to review how it should have been done. If you modify your staking now, I believe your tree eventually will stabilize. Generally, it takes one growing season to accomplish this.

Q: We live south of Houston and planted a river birch last year. Unfortunately, we had a drought last summer, but we made sure the tree had water. This spring, it leafed out fine, but I just noticed that the bark is gone on four to six areas of the trunk. It is not recent because the exposed wood is gray and dry. However, there are areas with damage beneath the bark at the cambium layer (I think). This leads me to believe something is inside. The damaged areas are 1 to 2 inches in diameter and there are small, black insects running around the damaged areas. There also is what appears to be a wood-damaging insect because there is powdered wood at some of the areas. There has been no leaf drop and the tree looks fine. Oddly enough, the damaged areas are on the back side of the tree away from our normal viewing angle. Is the tree a loss or is there some kind of treatment I can use? I thought the tree was resistant to bugs. (email reference)

A: You should get in touch with the Extension agent in your area to get assistance on this. Keep in mind that resistance does not equal immunity. Frankly, I’m surprised to know that river birch will grow in the Houston area. It sounds as if there is some borer activity going on with your tree. You should take corrective action using a systemic insecticide before too much damage occurs. Because your tree is small, you could spray it with a product, such as Orthene or Isotox, that has some systemic and contact effectiveness. However, please get in touch with your local Extension agent. Go to and click on your county to contact the agent before taking any action involving pesticide use.

Q: I hope you can help our poor trees. We have four trees that are approximately 30 years old. Last year, one of them developed yellow spots that had a dustlike consistency. All the leaves fell off but grew back a few months later. This season, we have noticed that the yellow spots have come back with a vengeance and started to infect the neighboring poplars. What do you think this is and what can we do about it? (email reference)

A: This is a rust fungus, which is an obligate parasite. This means it must have an alternate host nearby to complete its lifecycle. In this case, the alternate host would either be a hemlock or a larch, which are both conifers. If you have any on your property, they should be removed to break the cycle. If they are off your property, the only option you have is to put down a protective spray using a sulfur-based material such as Mancozeb or other products labeled for this pathogen. Raking up and burning all fallen leaves also will go a long way in minimizing the virulence of this disease.

Q: I came upon your website while I was looking for information on moving my raspberry plants. We live in the Willamette Valley of Oregon (Zone 8a) but are moving to Bend, Ore. (Zone 6a). Our lot is located in a banana belt for this town because it is protected from the wind and is south-facing, so it gets lots of sun. Anyway, my plants are very vigorous and ever-bearing. I have dug up plants in years past and put them in a pot to give to friends. The plants have done well during transplanting and have even fruited in the same year. I dug up enough plants to fill 10 pots. So far, the plants are looking good. However, I do not have a place on our new lot to plant them, but I have next-door neighbors who have a new garden bed and have volunteered to take them and keep them watered. I'm wondering how long they could be heeled in that bed and how soon I should plant them. Could they be heeled in for a whole year? These plants grow very tall. However, they'll be in a colder climate, so they may not get as tall or bear as much fruit. I would love to hear what you think. I would like to preserve these plants at all costs. (email reference)

A: For sure, heeling in is a temporary move that is not intended to last a full year. I would encourage you to get them moved to their permanent location at your new home as soon as possible. While it is true that plants survive winters in their containers all the time, it puts them under undue stress that may have repercussions later on. You location is in raspberry heaven territory. However, just because you are, don't stretch your luck too much.

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 email

NDSU Agriculture Communication – June 20, 2012

Source:Ron Smith, (701) 231-7971,
Editor:Rich Mattern, (701) 231-6136,
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