Questions on: Cottonwood

Ron Smith, Horticulturist, NDSU Extension Service


Q: There is a large cottonwood tree on the vacant property next door. The owner of the lot cannot be located. I have a very large root growing in my yard and it is starting to compromise my pool. Is there a way to kill the tree from the root in my yard? (e-mail reference)

A: Rather than do that, I would encourage you to contact the city forester to see if there is a legal and safe way to have the tree removed. Perhaps you can get an "abandonment of property" declaration to get it done. If that is not an option, then get a contractor or arborist to cut the root back to the property line and then install a root barrier at that point.


Q: I will remove an old cottonwood tree in my backyard to build a garage. I was told I should grind the stumps about a foot below soil level. What do you think? Thanks. (e-mail reference)

A: Grind until there is no stump left, whether it is a foot deep or more. Be sure to get all the grindings cleaned up before building the garage over the area.


Q: I had an inquiry about cottonwood branches breaking off. However, the branches that are breaking off are not main branches at the trunk. The homeowner said that the trees are watered. I saw a few samples of fallen branches that looked very healthy to me because the branches were green and wet. I asked him if the trees rub against each other or if he noticed more loss after heavy winds. He said no to both questions. Do you have any idea why a cottonwood would lose branches like this? (e-mail reference)
A: Branch drop or "free kindling," as I like to refer to it, is common with some species of trees. Poplars are among the most notorious for doing this. It generally is not associated with any disease or insect problems, although both can contribute to the branch drop as well. Willows and weeping birch also typically shed branchlets.


Q: I enjoy your articles. I have lots of diseased elm trees that need to be removed, but I am confused about what I should plant in place of the elms. The new plantings would be used as a shelterbelt, so I want some fast-growing trees that have a long life expectancy. Will a row of lilacs and a row of cottonless cottonwoods work? I’ve had good luck with them before. I am short of space, but I could squeeze in another row. Is the cottonless cottonwood the same as a poplar or is that a different tree? I read that cottonwoods also have disease problems. (e-mail reference)

A: Thanks for the compliment! Any tree is going to be subject to pathogens and insects. Some are more prone to problems under certain conditions than others. If you have had good luck with cottonless cottonwood (poplars) and lilacs, then continue to use them.


Q: I was hoping you could advise me about transplanting cottonwoods. We're located on a ranch in the sand hills along the Nebraska/South Dakota border. We'd like to plant cottonwoods for shade and windbreaks in our pastures. There are hundreds of little cottonwoods by our house that we could transplant. When would be the best time of year to dig up the trees? When would be the best time to plant? Can they be stored for some stretch of time while they are dormant? (e-mail reference)

A: The digging and planting time should be as close together as possible for maximum tree establishment. This would be in the fall after they have gone dormant or early spring before they break into new growth.


Q: What is the best way to plant a cutting from a seedless cottonwood? (e-mail reference)

A: Depending on the tree's vigor from which the cutting was taken, root it during August under an intermittent mist system or mist frequently every day. Plant the cutting in a sand/peat mixture under partial shade. Dipping the cutting end in a rooting hormone prior to sticking it in the ground will improve its rooting time.


Q: Why are the cottonwood trees in our city losing leaves and sometimes their branches? The leaves are still green for the most part. This is happening all over our city and no one seems to know why. (Valley City, N.D.)

A: A couple of maladies can cause this to take place. I have a laundry list to select from, which could be any or all causing the problem. The problem could be happening because of the extended drought conditions. Cottonwoods and hackberry trees often will drop leaves and branches as a means of conserving water. It could be called “drought dormancy.” This dormancy keeps the trees from dying during a stress period. Twig girdlers and twig/branch pruners are two insects that will attack trees under stress. Their egg-laying activity or larval feeding can cause twigs to drop. Petiole galls and twig galls are caused by insects and their feeding activity. The galls weaken the tissue surrounding the stems or twigs. There might be a few more that I cannot think of at this time, but these are the major causes of this problem.


Q: We had some willow and cottonwood trees cut down this spring. I would like to know what the best method is to kill the sprouts. Removing the stumps is not an option right now. (e-mail reference)

A: Spray any sprouts that come up with Roundup. Drill holes in the stump and fill them with saltpeter.


Q: I have a cottonwood I planted from a cutting a couple of years ago. The original planting was damaged and I soon had two thick branches growing instead of one main trunk. The tree splits about 2 feet off the ground. Can I cut off one of the branches or is there a way to do this in stages that would be better? (e-mail reference)

A: You can and should remove the branch; otherwise it will be a source of further problems. Totally remove the branch so the wound will have a chance to start healing.


Q: I have a big problem. The trees at the end of my block are cottonwoods. They are shedding cotton, which seems to fall mostly on my lawn. It looks like it has snowed for several days. Unfortunately, it rained hard each evening and washed the seeds into my lawn and bark dust. How do I get rid of the sprouts that are coming up in my bark dust without killing my ornamental plants? I have thousands of little shoots starting to grow. Any suggestions? (e-mail reference)

A: The easiest way I control such minor annoyances is to rake or hoe them lightly. They are seedlings and easily can be controlled at this stage of life. As to the lawn, normal mowing will take any out that may germinate.


Q: We have a cottonwood tree in our backyard. Every April, the tree releases very sticky needles. The needles get stuck in our dog’s paws and in the carpet. Is there anything we can do to eliminate these sticky needles? (e-mail reference)

A: You need to contact an arboriculture company that has the ability to spray a growth regulator. Spraying will inhibit seed formation.


Q: I just received 25 cottonwood trees from my state’s conservation department. They are wrapped in some nice packaging. How long will these trees survive in this packaging? What do I need to do to ensure their survival before I plant them? Can I plant them and then transplant them after two to three years? Will they survive at their new location? Any help in these areas will be appreciated. (e-mail reference)

A: The trees can stay in the packaging for a few weeks, assuming they are kept refrigerated or in a near-freezing location. Yes, they can be transplanted successfully, if it is done correctly. In the meantime, don’t allow them to dry out. Get them into the ground before the buds break.


Q: I was told (by a new acquaintance) that planting native cottonwoods is regulated in many North Dakota communities because the cotton is considered a nuisance. He added that in 100 years we won’t have any native cottonwoods left. Can you verify or comment on what I was told? We have Populus deltoides here at Wind Cave National Park, which we are trying to save with the assistance of a wildlife enclosure. I am interested and concerned about efforts to limit the species in other areas. (Hot Springs, S.D.)

A: I agree, cottony cottonwoods are a nuisance, but I have not heard of a ban on them in any North Dakota community. I also have not heard any statements about the native species not being around in 100 years. Sorry I couldn’t be more helpful!


Q: I have several cottonwood trees I would like to remove. Three of them are next to electrical boxes. The tree removal service I contacted will remove them but will not grind the stumps. Is there anything that I can apply to the stumps that will kill the root system? I can’t afford to have new sprouts popping up. (e-mail reference)

A: Stump grinding will not prevent the roots from sending up sucker growth. What you can do is rent a stump grinder yourself from a local rental store. A material called Salt Peter can be applied that will accelerate the death of the stump and roots. You also can get a product known as Sucker Stopper – RTU, which will prevent sucker growth from coming back.


Q: I am hoping you can provide me with the name of a product to apply on cottonwood suckers growing in my lawn. (Onida, S.D.)

A: I’m assuming the roots are still attached to the tree that you want to keep. If that is the case, locate some RTU Sucker Stopper. It may be available in a local garden center. It can also be found at www.montereylawngarden.com or call (559) 499-2100. They are located in Fresno, Calif.


Q: We’ve received a lot of calls about cottonwood trees dripping a sappy liquid. Is this something that can be treated with insecticidal soap? If so, where do you purchase the soap and how is it applied, especially on very tall cottonwood trees? (e-mail reference)

A: The problem is usually caused by aphids. Spraying with insecticidal soap will take care of this pest because they are soft-bodied and vulnerable to low-toxicity insecticide. Any garden supply store, nursery or garden center should have it. On large trees, there is no other way to apply insecticidal soap except using a high pressure sprayer that is available only to professionals in the business. Sometimes predatory insects arrive and begin bringing the aphid population under control, but this is a hit or miss situation.


Q: I have a cottonless cottonwood tree in my front yard. It is about 100-feet high and stands in front of our house. There seems to be something eating away at a limb we had partially removed a few years ago. I don’t see any bugs on the outside. I have painted the limb with pruning paint in hopes that this might seal the holes, but it isn’t stopping the problem. (Dickinson, N.D.)

A: I would suggest contacting Craig Armstrong in Dickinson. He has a degree in forestry and works for the city. He can tell you if the tree poses a property hazard. That is something you don’t want to take chances with, so an on-site visit is needed to be on the safe side.


Q: We transplanted a cotton wood tree in the fall two years ago. It did fine last year. Last fall I wrapped the trunk with one of those paper tree wraps to keep a cat we have from killing it by sharpening its claws on it. When I took the paper off this spring there were about 10 places underneath where little green branches had tried to form and were light green with a black kind of rotting at the ends. I cut those off hoping it would force the upper leaves. The tree had buds but never leafed and the buds looked like they have been dipped in sap. At the base it now has branches that are growing fast and have huge leaves. Is the rest of the tree dead? Should we cut it off above the branches at the base? (Sully County, S.D.)

A: It sounds like your tree is a goner. Some people have had good luck developing a tree from the sprouts that emerge from the base of an otherwise dead tree. A girdling canker or borers got to the upper part of the tree.


Q: My daughter planted a pair of cottonwoods on both sides of a horse jump. It was a silly idea, but she did it anyway. The cottonwoods have now almost grown together, rendering the jump unusable. I know that summer isn't the ideal time to prune, but it's not an absolute no-no is it? I was thinking of pruning 35 to 40 percent of the branches and leaves. Is that too much? Do you think painting the wounds with pruning or some kind of paint is necessary? I don't know how inclined they are to getting pests. (e-mail reference)

A: There are better times than others to prune. It all depends on what the objectives are. Removing more than 30 percent of the crown at one time could cause problems. Alex Shigo, a forester of renown, has proven that coating the pruning wounds is not necessary. It has been shown to inhibit the natural compartmentalization that takes place after a pruning wound. His motto was that properly pruned trees don’t need pruning paint, while all the pruning paint in the world won’t make a difference if the trees weren’t properly pruned. Cottonwoods are inclined to get pests such as diseases and insects, so be sure your pruners are clean.


Q: I have a large cottonwood (cottonless) tree in my yard. The tree splits into two major trunks just above the ground. Last year one side of the tree lost most of its leaves early and the branches looked like they had died. This year that side of the tree is slow to get leaves and looks half dead. What could be causing this? (Minneapolis, Minn.)

A: It could be armillaria root rot, girdling cankers or a vascular disease like verticillium wilt. Have an International Society of Arboriculture certified arborist inspect the tree. There is a chance the tree can be saved, but not likely. More importantly is the potential hazard such a declining tree may pose. The arborist could identify the potential hazard and offer suggestions on pruning or partial removal.


Q: Last fall I had a 70-foot cottonwood tree removed and its stump ground down. The stump grinding did not take care of the many roots running through my yard. This year I have shoots coming up all over my yard. I've tried cutting them as well as spraying with Roundup, but it doesn't seem to have any effect. I am hoping to re-landscape my yard and put down sod. Currently this looks to be impossible. (e-mail reference)

A: Get a selective shrub/brush killer at the local garden center. It should contain a compound known as dicamba, which, when applied to the leaves coming up on the suckers, will be translocated to the roots and kill them. Don't expect that one application will solve the problem. A 70 foot cottonwood has a very extensive root system. The roots have plenty of stored carbohydrates, the safety net for the tree's survival. Plan on spending the summer applying the compound, with your sod installed sometime in mid -September. Make sure the material you use is not toxic to the turf and don't be tempted to do revenge spraying by making the mixture stronger than is indicated on the label. That will only burn the foliage back and not be translocated.


Q: I read recently that the product Florel (Ethephon) reduces cottonwood tree cotton production. The trees in our yard and those of our neighbor’s produce lots of cotton for about four weeks. (e-mail reference)

A: Yes, Florel will reduce seed production (cotton). You will likely have to hire a professional arborist to do the job, but it may be worth it to keep from being buried in cotton every spring. Regional timing is important, hence the recommendation for the arborist, plus they have the necessary equipment to adequately cover the trees.


Q: One of my cottonwood trees is slow to leaf out and some branches appear dead. I'm sure it must have some type of insect and I don't want my other cottonwood trees infected. Should I cut the tree down? (e-mail reference)

A: Wait! There are many reasons that a tree is slow to leaf out. Yes, it could be insects or disease, but it could also be environmental damage. Get a proper diagnosis before doing anything. You wouldn't want to spray for insects if the problem was a fungus. You can decide what to do after a proper diagnosis. If it is an insect or disease, then removing the tree is definitely an option. But it's not the only option. Trees are pretty resilient. Give it a few weeks and see how its doing before you decide anything. (JZ)


Q: We have two very tall cottonwoods in our front yard. For about three years they have been losing chunks of leaves during the summer. I contacted many people but they gave the same answer that you did; this is normal. We now have more dead branches then live and they look awful. One Web site I went to said shoot blight could be the problem. The clumps always had a black glob on them. (e-mail reference)

A: Based on what you described, it does sound like leaf blight and/or shoot blight. A professional diagnostic lab could culture a sample and let you know for sure. And yes, normally this doesn't cause major damage unless it occurs on the same branches for several years, as you indicated. Prune out the dead branches and rake and remove the infected leaves each fall. Copper-based fungicides may provide some protection, but you may not be able to provide adequate coverage if these trees are already very tall. Good luck. (JZ)


Q: We have four cottonwood trees in our back yard. They are great shade trees and we love them. Like everyone else I hate the cotton that comes off the trees. A local green house owner suggested using a product called Florel to cut down on the cotton. We sprayed it on our trees last year and cut the cotton production down by 85 percent. The only side effect I have seen are fewer leaves on the trees, but this could be caused by the drought we’ve been having. (E-mail reference)

A: Florel supposedly reduces crabapple fruit production for those who do not want so many messy fruits, but this is the first I have heard of it being effective on the cotton that comes off the trees. I was curious so I looked up the label and sure enough it is labeled for cottonwoods. I know a lot depends on timing, so apparently you got it just right last year. Let's hope you are as successful this year!


Q: I have a cotton-less cottonwood tree that I planted last year. The tree was growing extremely well. This year it started to bud, but then we had a cold spell. The buds are still there, but no leaves. All of my other trees of various species have leaves. (Email reference)

A: Be patient, this is just a setback and not the end of the tree's life. Check the cambium just under the bark. If it is still green, buds will probably develop again in two or three weeks.


Q: We have a huge cottonwood behind our house. This tree is so large it looms over our home. A man who painted our home told us that cottonwood trees are known for snapping and falling down. Is this true? (E-mail reference)

A: The painter may know what he is talking about. They are notoriously weak wooded trees. I would suggest that you get an International Society of Arboriculture certified arborist out to inspect the tree and assess the potential hazard it may pose.


Q: How do I dig up volunteer cottonwoods and plant them at another location? They would have to be barerooted. What size cottonwoods can be moved this way and how much root needs to be taken? (E-mail reference)

A: The smaller the better and the more roots the better. When the size goes up so does the difficulty in moving them, more root system is lost, and the survival rate drops. It would be best if you could get some one to two inch caliper material. Plant them at the same depth and water in well.


Q: We have lots of native cottonwoods growing in our area. We dug up four of them and planted them in our yard. How far should they be from the house so the roots won't be a problem with the foundation? Is the cotton the tree drops a problem? (Watford City, N.D.)

A: The roots will only be a problem with the foundation if there are cracks in it. Otherwise, you have nothing to worry about. I have received hundreds of letters over the 18 years I have been writing this column complaining about the cotton and wanting to know how to eliminate it. Cut them down has always been my answer. I have yet to receive one letter that says the writer loves the falling cotton!


Q: The roots of our cottonwood tree are taking over the lawn and approaching our concrete patio. Should we attempt to take the tree out? (E-mail reference)

A: You should contact an International Society of Arboriculture certified arborist. A certified arborist is bonded and insured and can do the job in a professional way by cutting down the tree and then grinding the stump and most of the major roots.


Q: When is the best time to prune cottonwoods, Austrian pine and pinon? (E-mail reference)

A: In the early spring before new growth and after the candle growths have elongated and the needles have just begun to pull away.


Q: We have five cottonwoods in our backyard that are 75-to 100-feet tall. They provide good shade but they started dropping leaves in August for no apparent reason. The leaves that are falling have a gall on the leaf stem. Inside the gall are some sorts of little critters. The leaf problem is so severe that we are considering having them cut down. (E-mail reference)

A: Please don't sacrifice those mature trees for the small problem you have. Contact a Certified ISA Arborist and have the trees sprayed next spring. The petiole gall forming insect is an aphid that causes no harm to the tree other than premature defoliation. The arborist will very likely come out next spring before leaf bud break and spray with dormant oil and possibly follow up with an approved insecticide. It could very well be the only showing of this insect, as natural predators may move in and keep them under control next year. Generally, an early dormant oil spray will take care of any remaining insects. Try to clean up as much of the fallen leaf litter this autumn as possible.


Q: I have a large, old cottonwood tree in my backyard that is probably 50 years old. It sends up shoots on the exposed rootballs all over my yard. Is there anyway to discourage these shoots while not harming the tree? (E-mail reference)

A: Use a material called Sucker Stopper RTU. It is available at some retail outlets. You may want to contact the company directly to find the nearest location. They can be reached at Monterey Lawn and Garden Products, Inc., Fresno, Calif., (559) 499 2100. Or contact them on the Web at: www.montereylawngarden.com  . It is fairly pricey stuff so use it with discretion.


Q: I have a very mature cottonwood tree (70 feet) in my backyard. Since it provides shade, I'd like to keep it as healthy as possible. There are two very large roots that I would like to cut since they are near a concrete patio. One has broken through the surface and the other is a couple of inches down. Will cutting these roots hurt the tree? (E-mail reference)

A: I cannot answer that question without seeing the tree and checking it out. I would advise getting a hold of an International Society of Arboriculture certified arborist to check the tree over before you make such an arbitrary decision. You don't want to cut something out that will result in an imbalance that could cause it to fall during the next storm.


Q: When our lake lot on Golden Lake in Steele county was leveled and excavated, we opted to keep a few of the dominant trees, which are mostly cottonwoods, at the waters edge. That meant that we had to leave a good deal of sand in that area, basically trying not to disturb the root systems of the trees. I have tried to grow perennials/annuals but haven't been satisfied with the growth of anything, except sedum. I have two Russian sage plants, planted three summers ago, which reached an all time high this summer of around 4 inches! I dug away large areas of sand and filled with good soil from our farm but the water runs off or soaks down through the soil. The soil is always dry even with the excessive rainfall we've had this summer. My husband thinks I need to build up the area by a foot or so and perhaps put a layer of plastic between the sand and new soil. Because of all the tree roots, it's not possible to remove all the sand. I think his idea sounds stupid but I guess I'll try anything. Planting all succulents in that area is a last resort for me. (Portland, N.D.)

A: The best cure for water retention is organic mulch. That way there is a balance of water and air in the root zone that will support plant growth. I suggest incorporating generous amounts of sphagnum peat moss into the soil, planting, then topdressing it with shredded bark mulch. That is a much more ecologically sound approach.


Q: I have some cattail slough land in South Dakota that is bordered by several expansive and very dense cottonwood groves. These naturally occurring groves have trees that are about 15 feet high so they are fairly young. Should I thin out the groves so that I will have some mature cottonwoods that are spread out at a more desirable spacing? (E-mail reference)

A: Positively! Go for it and good luck.


Q: One of our cottonwood trees has a scattering of leaves that are turning yellow and falling off. The trunk is developing long cracks, especially in the bark but some are deeper. There doesn't seem to be anything coming from the cracks. I can’t find any insects or eggs on the leaves. Any ideas? (E-mail reference)

A: Have an International Society of Arboriculture certified arborist come out and inspect the tree for soundness. You didn't indicate the age of the tree but I gather it’s up there in years. Cottonwoods are notorious for having problems as they age. If the problem is caught early, it can usually be corrected with minimal expense.


Q: Approximately how many days or weeks does it take for a cottonwood tree to release all its cotton? My house looks like it is ready for Halloween but I don’t want to wash it until we are at the end of the cotton season. (E-mail reference)

A: Most, if not all, should be gone in about 10 14 days depending on the weather and vigor of the tree.


Q: Could you please tell me the average amount of water that a large cottonwood tree uses per day? The trees are near a river and irrigation ditches. (E-mail reference)

A: It can vary all over the place. If they are growing in an arid climate, it will be higher due to the transpiration pull being greater than in a more humid region. It also depends on the wind speeds the tree encounters along with other vegetation in the tree's region. Someone apparently calculated that the "average mature deciduous tree can consume over 200 gallons of water per day in the peak of the summer." I have no idea where that summer was but at least it’s a starting point for you.


Q: In the spring of 2000 we planted Siouxland cottonwoods which did very well but last spring (2002) we had 18 trees die. The rest did well last summer but this spring we had more die. The trees are at least 8 feet tall and are dying from about the one-foot level and up. We have been tilling the tree rows so there is no grass or insulation near the trees. Could they be dying because there is a lack of snow cover? Should I cut the dead branches off and see what happens? The main trunk seems dead except for branches near the bottom. The roots must be somewhat healthy to be keeping a few branches alive. (E-mail reference)

A: Go ahead and cut off the dead material and go lightly on the tilling. Too much too close will damage the roots and set the plant back. Siouxland is a poplar that has a whole encyclopedia of diseases that can debilitate it. Usually it doesn’t occur this early in a planting. Diseases mostly happen when they are just starting to be of value to the owner. Your dieback could be due to any number of problems, including the weather.


Q: My cottonwood tree shed some small brown capsules in mid-April. Many of them landed on my car and stayed there. They were coated in some sort of sticky stuff. When I removed them from the car, some of the sticky stuff stayed on the paint. I haven't found anything that will remove it. Do you have any ideas? Right now, I'm just a bit upset with that big, old tree. (E-mail reference)

A: A good multipurpose wax should do the job along with a good buffing. The seed capsules are bound to be sticky and the sap will leave a light etching on the car's paint but it can usually be buffed out. Contact your local car dealer to see if they have anything that can help you get rid of the marks.


Q: Our huge cottonwood trees are blooming with lots of those ugly pouches (seeds/future cotton). Is there anything we can do to get rid of or inactivate them so we don't get that awful cotton this summer? (Buchanan, N.D.)

A: If I could solve that problem, I would be the most generous philanthropist in America! As far as I know, this is something we must live with if we are going to have these trees in our environment.


Q: I have two extremely annoying cottonwood trees in my back yard. During the month of June I can't even go out to the pool because the fuzz is coming down like a snow storm and clogging the filter in my pool. I intend to eventually cut them down, but for now I just want to kill the female. What poison do you recommend? (E-mail reference)

A: A chain saw. Let it leaf out first, then cut it down. That will reduce the number of sprouts coming up from the roots. Spray Roundup or any broadleaf herbicide like Trimec on sprouts that do come up.


Q: I noticed on your Web site that you seem to be the answer man for cottonwood questions. I was wondering if I could pester you with one. We have been lucky enough to purchase a property with several beautiful cotton-less cottonwood trees. This property also has a treeless creek. We would like to use our existing trees to populate the creek. We've read that cottonwood cuttings are easy to root and transplant - cut them in the dormant stage and plant in spring. However, we've also read that they shouldn't be planted in a pot because the roots grow so quickly. So how does the timing work? If you have to wait until spring to plant, but you can't plant them in a pot after you cut them, how do you keep them from dying? (E-mail reference)

A: Don't worry, they will grow. Just get them planted before new growth emerges in the spring by carefully knocking them out of the pot and planting them at the same depth.


Q: We live in Minot and are planning a wedding on June 21. It will be a garden wedding. Will the cottonwoods be dropping their seeds and cotton at that time? (Minot, N.D.)

A: I'm pretty good, but not that good! So much depends on the weather - they could or could not be dropping their cotton at that time. There must be someone who is a Master Gardener in that area who keeps track of such occurrences. I suggest checking with Ward County Extension agent Mike Rose to see if he knows of anyone who is a good record keeper of nature's patterns of behavior. What you are asking for is the science of phenology which is the study of such natural phenomena as blooming time, fruit set, migrating birds, etc. I know in the old days gardeners took great pride in such record keeping. I don't know of anyone that does today. It seems life is too busy for all of us.


Q: I have a cottonless cottonwood that appears very hardy, but it has some white foam coming from the trunk. What is it and how can I get rid of it? (E-mail reference)

A: I think the "white foam" you are referring to is in reality evidence of internal wood decay, and what you are seeing are the fruiting bodies. These growths are an indication of advanced decay and are known as conks. I would advise contacting a local arborist to see if a determination can be made as to the safety of the tree.


Q: We have a 25-year old conttonwood tree by our house that seems to be in trouble. The trunk forks about 5 feet off the ground, and the bark is split and weeps a clear liquid. The bark is getting rotten. From the side it appears that the trunk is bulged where the split is. It grows in very sandy soil that is about 100 feet deep. No special care has been given to it. Now there is some leaf drop. There are many cottonwood trees below the house near our lake that my husband's grandfather planted when he homesteaded here around 1904. I love this tree and the branches are within reach of our second story deck so we hang bird feeders in it. If there is any danger that it is dying we would have to cut it down as it could fall on our house. A friend suggested that we drill a hole through the trunk below the fork and insert a long bolt with washers on each end to pull it together. (Wildrose, N.D.)

A: Your friend gave you good advice, but that is not something you should do. It should be carried out by an arborist who knows what is going on and can perhaps further advise you on what else needs to be done to preserve your tree.


Q: Is there any way of stopping or decreasing the amount of cotton produced by mature cottonwood trees? (E-mail reference)

A: Short of cutting the offending trees down, none that I know of.....sorry!


Q: We purchased a house last fall and in the yard is an enormous cottonwood tree. The house was built here in Minnesota in 1902 and we assume it was already here. We were waiting for the cotton buds to consume our yard, but they never did. I am wondering if that is any sign of an unhealthy tree, or if it could just be non seeding. Did that variety exist so long ago? Should we be concerned about the tree? (E-mail reference)

A: Good questions. Yes, you are one of the blessed to have a cottonless cottonwood tree. And yes, you should be concerned about any tree that age, especially if its collapse could harm property or limb. A checkout by a local certified arborist would let you know of the soundness of the tree.


Q: Is there a way to make my cottonwood trees stop producing cotton? I have three of them that are around 40 to 50 years old and any information about stopping the cotton would be helpful. (E-mail reference)

A: Short of cutting them down, nothing. Sorry!


Q: About seven years ago we planted two trees that were labeled "Cottonless Cottonwood." After seven years of no cotton, this year both have begun producing cotton. Why, now, have they started doing this? Is it normal? Will they now do this every year? Did we buy trees that were mislabeled? (E-mail reference)

A: Briefly; they are now mature enough to produce the "cotton"; yes and yes. Sorry.


Q: Last May I planted about 50 cottonless cottonwood trees around my property for a wind barrier. Only about five of them grew branches and got a larger base through the summer and fall months. Some look the same as the day I planted them while some broke at the base, and some were eaten by rabbits. Some broke half way down the base (trunk), and that is why I am writing this letter. I need to know how sturdy and hardy these trees can be. If the base gets snapped or eaten half the way down, will they continue to grow? And in regards to the trees that did not get much growth last year, were they possibly getting an established root system and will grow this year, or am I just wasting time and should plant new trees? I really do not know much about plants or trees but I think I planted correctly. I protected the roots and kept them moist until we planted. We dug deep holes and fertilized them and kept them watered. (E-mail reference)

A: My experience with cottonwood trees has been that once established, they are there in some form or other, for life and beyond. I would suggest giving these trees another year to shape up and show some vigor, then if not, recycle them and replant. With tree growth, how much energy is stored in the root system often determines whether or not they take off after planting. Of course, a tree may do a very good job of storing that energy, but then too much of the root system is removed in transplanting, setting the tree back for a year or so. Sometimes they can recover, other times they cannot. I would say that with this year, you will have given them ample time to recover from any transplanting shock. Don't make the mistake of over-caring for them. Give them water to keep them from dehydrating, but further fertilization should not be necessary.


Q: We are trying to locate a business that sells cottonwood buds. Do you have any ideas as to where to begin looking? (E-mail reference)

A: Not the slightest clue! Perhaps a reader will know and weigh in with the answer. If they do, I'll let you know.


Q: The cottonwood tree in my backyard has a branch that is forming (for lack of a better term) in two spots. What is causing this condition? Another question I have is what would cause six or so rust colored spots on the base of a cottonwood tree? (E-mail reference)

A: I think you mean that the branch is forming a "Y" crotch, which could be dangerous as the tree lays down more wood in that area with the developing branches. I suggest selecting one or the other and make that the leader. Generally the lesser of the two is selected to be removed. The rust-colored spots could be the result of slime flux, an exuding of the sap that has fermented in the interior of the tree, causing a build-up of pressure that causes the material to ooze out. Have the tree checked out by a forester or arborist to make sure the core hasn't rotted. These are my best guesses based on your have description.


Q: I have a cotton-less cottonwood tree that I planted last year. The tree is growing extremely well, although I am unhappy that it is not full. The tree is growing straight up and very slender. It has grown about 7 feet this season. Is there any way that I can make the tree become fuller, such as pruning the main trunk? (E-mail reference)

A: Yes, pruning the tip will cause the tree to lose the strong apical dominance that it is now exhibiting, giving the lateral branches an opportunity to grow and spread. I suggest doing it early next spring before the new growth emerges. Doing so now might encourage too much succulent growth that may not harden off before winter. Besides, the tree would be more susceptible to disease organisms at this time as well.


Q: My neighbor has a cottonwood tree his yard that keeps sending shoots up in my yard. I have killed them in the past with Roundup. The tree blew down last summer and all that is left is the stump, but the shoots are coming into my yard faster now. Is there some way I can kill the roots and life that is still in the stump so that it quits producing shoots in my yard? (Devils Lake, N.D.)

A: Try TRIMEC. It is more potent and translocates to the roots. Wait on mowing one day after spraying to allow for maximum absorption.


Q: People have been telling me for years that it is the female cottonwood tree (if there is a male and female cottonwood) that produces the dreaded cotton. If this is true; is there any way of telling which tree is male or female? This would save a lot of grief in unnecessarily destroying the volunteers which pop up on occasion. We like cottonwoods; just not the cotton. (E-mail reference, Wessington Springs, S.D.)

A: Yes, what you said is true. What you want to purchase is a male clone, like the 'Siouxland' poplar. As far as I know, there is no observational way to distinguish the sexes until it is too late.


Q: Do you have any information on stating when and how to trim young trees, especially silver maple and cottonwood? (Webster, S.D.)

A: Refer to the NDSU Extension Service publication titled "Pruning Trees and Shrubs" (H-1036). Pruning should have been done earlier in the spring, but now would be OK. You should have some sap flow, but it is nothing to worry about.


Q: Can you tell me why these clusters of leaves keep falling off of my cottonwood tree? What should I do, and what is causing it? It hasn't been producing cotton either. (Emery, S.D.)

A: The defoliation you are seeing is normal for members of this genus. Nothing can be done about it if you don't want to remove the tree entirely. A cottonless cottonwood is a blessing. Rejoice, at least, in that fact!


Q: Can you tell me what is wrong with my tree? I think it is a cottonwood. I also would like to know why my Larime strawberries are not bearing fruit? (Binford, N.D.)

A: Poplars or cottonwoods are prone to a plethora of diseases. In your case, the problem is Septoria leaf spot, a fungus brought on by rainsplash, humid weather, and poor air circulation.

Best control is sanitation—removal of all fallen leaves this autumn. You may want to try a fungicide next spring after the leaves open to protect the tree. Something like Daconil, Maneb, or Mancozeb would be good selections.

Your Larime strawberries should have set fruit by now. Perhaps you've fertilized too much or the soil is too high in nutrients. If they don't fruit next year, replace them (assuming you want the fruit and not the ground cover)!


Q: Can you tell me why the leaves are falling off of the enclosed sample of cottonless cottonwood in the first part of August? (Groton, S.D.)

A: Unfortunately, poplars have so many problems they have a book dedicated to the subject!

Two diseases have been common on poplar this year, which your sample shows evidence of: Septoria leaf spot and rust, two different fungi that are largely brought on by rainy humid weather and elevated temperatures.

The best controls are these: one, do not fertilize the tree, as this causes excessive succulent growth, which is more disease prone, and two, follow good sanitation, which requires cleaning up of all fallen leaves.

Next spring, spray the dormant tree just before leaf-out with lime sulfur. It is a good sanitizer and may help to control the disease problem.


Q: Enclosed is a leaf from a 40- to 50-year-old cottonwood tree, and it seems that the leaves are turning brown and falling off. The green leaves have a pod on them that is filled with some kind of bugs. (Seneca, S.D.)

A: The leaf sample you sent had leaf petiole gall aphid growth. This is a common occurence on poplar or cottonwood trees and, other than disfigurement for the growing season, causes no serious damage to the tree.

The other spots on the leaves are one or several leaf spot fungi that beset this poor species.

To control the gall aphid, spray the tree next spring as the leaves unfold with a systemic insecticide like Orthene. Controlling leaf spot diseases is almost a lost cause, but you may want to try Bordeaux mixture right after leaf-out.


Q. I have noticed spider mites on a pointed ivy houseplant and the morning glory that is covering all the walls of our deck. I sprayed it with Ortho Isotox with a pressure sprayer to get under the leaves twice, a week apart.

Two weeks later the morning glory was 40 percent yellow and losing leaves, and all my flowers around the deck were about wiped out.

I sprayed the morning glory again with ivory dish soap, diluted, three nights in a row, as well as the ground area.

Still, the leaves continue to be sucked of all life and drop. Also, my ivy inside is infested again. I had used Shult 2, Instant Pyrethrin, and it had worked for awhile. Is it something other than spider mites?

Also enclosed are branches from a nice bush next to the deck that is also infested. It must also be sensitive to the spray used. The brown spots weren't there earlier. It was a beautiful light green in June.

Lastly, we have 10 to 12 large (30 to 40 year old) cottonwood trees on our end of the block. The last week of August they dropped about a third of their leaves all at once. Was it the shift from three weeks of cold back to hot weather? Are they infested also? The leaves are spotty, but there is no "web" underneath.

This has been very discouraging so any assistance or advice would be greatly appreciated. (Aberdeen, S.D.)

A. I will give you an "A" for effort and for a partially correct diagnosis.

It looks as if you have some high salts in your soil or water supply, or poor drainage in the areas where you have been growing your plants. I suggest a good fall clean up after killing frosts and then incorporate generous amounts of peat moss to improve drainage. Soils in your area are typically high in pH, and the peat, especially if it is sphagnum, will help to lower it.

Morning glories are usually a piece of cake to grow and are often included in kids' garden kits.

You are obviously a very vigilant person and while that is generally good, don't overdo it.

Yes, the poplars will abscise their leaves following wide temperature and moisture swings.


Q: During the past four years, two cottonwood trees in our front yard have mites in a lumpy growth. When we noticed the problem, we were told they wouldn't
spread (which they did to another tree) and that they were only unsightly and wouldn't harm the trees. Now leaves will not grow where these growths are present.

The trees are about 30 feet tall, and the mites are now about half way up the tree. The second year we sprayed with Kelthane and an oil from a nursery, but they
were pretty well leafed out. Last year, it was either rainy or windy during the time they should have been sprayed, so we weren't able to do a good job again.

My questions are will we ever get control over this mite problem, or are we wasting our time? Will leaves ever come back on these lower branches? (Elgin, N.D.)

A: I would say it is time to remove the trees. When a problem is that advanced, the best hope is only for survival, not thriving growth.


Q: My neighbor has a cottonwood tree his yard that keeps sending shoots up in my yard. I have killed them in the past with Roundup. The tree blew down last summer and all that is left is the stump, but the shoots are coming into my yard faster now. Is there some way I can kill the roots and life that is still in the stump so that it quits producing shoots in my yard? (Devils Lake, N.D.)
A: Try TRIMEC. It is more potent and translocates to the roots. Wait on mowing one day after spraying to allow for maximum absorption.
Q: Is there a way to eliminate or at least significantly reduce the amount of cotton that a cottonwood tree produces? I was surfing the Internet today and came across
a comment from a man who heard there is a method out there that has "something to do with injecting a chemical into the ground that acts as a sort of 'birth control'
that keeps the tree from producing seed." (e- mail)

A: Beware of birth control products for trees!! I doubt they work at all. I have never heard of any product that does this effectively.


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