Questions on: Cherry

Ron Smith, Horticulturist, NDSU Extension Service

Q: After a 10-year battle, my Canadian cherry finally lost its fight with black knot. I had it professionally removed last week. I am tempted to replace it with another Canadian cherry, but realize there is a significant risk of disease. If the old tree was removed and the stump ground up, is there a risk the ground will recontaminate the tree or is this an air-borne pathogen? There are no other Canadian cherries as far as the eye can see, so I don't know how the tree got it in the first place. It did take a long time before it became diseased. I've considered pursuing alternative cherry trees, such as the Merlot, which is a recent, sturdier cultivar, but is not available in multistem. Are there disease-resistant red cherries or is this a lost cause? (e-mail reference)

A: It's a shame you lost such a beautiful tree. However, you have become a conditioned warrior in the battle against the black knot disease, so I encourage you to follow your dream and get another one. This time, follow preventative maintenance by spraying the new plant with lime-sulfur every spring while the tree is dormant. Spray the tree again when it is in full bloom with a fungicide containing thiophanate-methyl (Topsin, Fungo or Cavalier) as the active ingredient. Be sure to spray while the bees are not active. Read the label to make sure the formulation is cleared for chokecherries. Repeat the spray again 10 days after petal drop. This fungus is spread by rain splash, wind, insects, birds and humans. The fact that you have no visible chokecherries in the surrounding area shifts the statistical advantage for not getting the disease again in your favor, but maintain good vigilance. The problem typically has been overplanting of this particular species because of its beautiful spring flowers and the fruit that is relished by wildlife and jelly and wine makers. Another problem is that people wait until the disease has gotten out of hand to do something. People tend to plant a tree, water it and, if it appears to be doing all right, pretty much ignore it until the symptoms become almost overwhelmingly obvious. Then it becomes a fire alarm to try to save the tree. Go for it and good luck!

Q: After scouring the Web looking for help with my Canadian red cherries, I found your site and was impressed. I live in a suburb of Denver that has clay soil. My neighbor has a red cherry pruned as a tree. It is full, robust and about 20 feet tall. I bought two red cherry trees two years ago. I had the nursery plant them in our backyard. The holes were dug to their specifications and I had them backfill with clay-buster soil. At the time, the leaves were somewhat small and sparse, but I was told that within the next two seasons, the trees would fill out. It's two years later, but the trees still look sickly. The leaves are small and many are sort of folded. About 10 percent of the smaller branches are bare. Of the branches that have leaves, some seem to be burdened by their own weight. The branches are almost doubling over because the leaves are concentrated on the ends. I haven't been running the sprinklers or directly watering this year because of the abundance of snow we had. I have not observed any insect infestation or signs of the dreaded black knot fungus. The nursery has been no help. Should I prune the leafless branches? Do Canadian red cherries thrive with more or less water? Is there a fertilizer or tree food that may help? I welcome any other suggestions you may have. (e-mail reference)

A: First of all, I think the nursery should get a good dressing down for not standing behind its plantings and for delivering subpar trees. It sounds like the root system was deficient or damaged when the trees were planted, which would explain the crown thinning and the poor leafing out. I would encourage you to go back to the nursery to work out some kind of compromise on tree replacement. You should pick out the trees to be planted. Look for nice, full crowns, with normal-sized leaves. If they are decent businesspeople, they should meet you at least halfway on this. If they refuse to work something out with you, the Better Business Bureau should hear about their less than ethical standards. Next time, go elsewhere for the trees you want.

Q: I planted a bing cherry in my front yard last fall. This spring it was blooming and flowering, but all of a sudden the leaves and flowers turned brown and died. The rest of my fruit trees are fine. Any ideas as to what may have caused this? Thank you. (e-mail reference)

A: It could be trunk girdling by bunnies or voles or verticillium wilt, which is a vascular disease that blocks water-conducting tissues. Sorry, but you now have cherry firewood.

Q: My mother has a Canada red cherry tree in her front yard that sends out suckers everywhere. Is there anything that we can do to get rid of the suckers without killing the tree? She has a newspaper article from your column from several years ago about this problem on a different kind of tree. At that time, you recommended a product called Sucker Stopper RTU. She has not been able to find it and someone told her that it probably would kill the tree if you treat the suckers. Please advise us as to what to do! Thanks. (Carrington, N.D.)

A: Sucker Stopper RTU wouldn't kill the tree, but she would go broke attempting to control all of that growth. The stuff is expensive and good for just one season and only stops the sucker growth at the point of origin. There is nothing I can recommend to use that will kill the suckers without the possibility of eventually killing the tree.

Q: I have an old cherry tree that has the best cherries I have ever eaten. The bark is peeling off in huge layers and the overall appearance of the skin is very rough. It has these gems on it that I've been told is the problem of whatever is going on. From talking to people locally and reading on the Web, I believe it is bacterial canker that has no known cure. These jewels are on the trunk of the tree, so pruning would mean cutting it down. Can you help me? Thanks. (Sacramento, Calif.)

A: If it is a bacterial canker on the main stem, then the tree is lost and you are better off cutting it down.

Q: I have an old Japanese cherry tree. It's doing great, but the bark has split open to about the size of a pencil eraser. The split is about 5 feet long. Do you recommend that I put something in the crack or leave it alone? Thank you. (e-mail reference)

A: Leave it alone for now. This fall, wrap the trunk of the tree up to the lowest branches with a tree wrap paper or plastic sleeves. Both can be purchased from local garden outlets. What you have is called frost crack or is sometimes called sunscald. This problem typically shows up on the south or southwest side of thin-barked trees. The tree will work to heal itself, so adding anything to the wound only would delay the healing process or create even greater problems.

Q: I live in California. I have a tree with three varieties of cherries on it. All three have two ruby red nubs at the base of each leaf. Ants really like the nubs. Are they part of the tree or is there something else going on? Thank you. (e-mail reference)

A: Some of both. From your description, these probably are leaf petiole galls that are secreting honeydew that the ants are harvesting. They could be aphids or scale insects doing the honeydew secreting. I would get what they are identified by someone locally so that you can take corrective action if the problem is aphids or scale insects or not worry about it if what you have are galls.

Q: I have three flowering cherry trees in my yard that were blooming when we planted them more than a year ago. We were very disappointed after none of the trees bloomed this year. We would like to do whatever we can to encourage blooming next year. Any idea why a cherry tree wouldn't bloom and how we might encourage bloom next year? (Bishop, Ga.)

A: Cherry blossoms are separate from the leaf buds, which makes the blossoms more vulnerable to unexpected swings in the weather. Your region of the country could have had an early warming spell that dehardened the buds enough that it killed the flowers when the next cold snap arrived. Apple trees have a mixed bud, which means the leaves surround the apple blossom. This gives them a little more protection and are less vulnerable to becoming prematurely dehardened. About the best thing you can do for next year is to not overfertilize or overwater. Allow the trees to go into winter in a tough, hardened state. This may be enough to keep the buds from being so vulnerable to shifts in spring temperatures next year, so you might get the blooms and fruit you want.

Q: We have a lovely north star cherry tree loaded with fruit that we would like to harvest. How can I tell when the fruit is ready to pick? We live in Bismarck, which is the land of drought and heat. (e-mail reference)

A: The fruit should be ready to harvest by now with all the heat we've had. However, no matter how long you leave the fruit on the tree, the fruit will be sour. It should make excellent jelly or convert nicely into wine.

Q: As a North Dakota resident living in the Turtle Mountains, what chance do I have of growing one or more varieties of Japanese cherry trees? According to National Geographic's "Field Guide to Trees," they are hardy to zone 4. I understand the trees thrive in the Pacific Northwest. With the substantial snow cover we receive, I thought that maybe, just maybe, I might have some success. Also, do you have some information about Tibetan cherries? I greatly appreciate your time and any advice you may have (certainly nothing wrong with a flowering crabapple, I guess.) (e-mail reference)

A: As you say, maybe it will survive and produce flowers for you. It depends on how much of a challenge you like. As you say, there are lots of flowering crabs that establish much easier and are every bit as attractive.

Q: I have a Canadian red cherry tree that provides beautiful shade for my house, but the tree has black knot fungus. I’ve had professionals here to treat the disease with deep-root fertilization, but the disease continues. Every year I remove the limbs that have the black knots. This year the tree is weeping globs of sap from the main trunk and secondary limbs. It breaks my heart to have to destroy this tree, but I do not think it's going to make it another year. Any input on this would be appreciated. (e-mail reference)

A: As what often happens with plants, when a primary pathogen weakens the plant, such as this cancer does to this tree species, secondary pests (in this case borers) move in for the kill. I'm sorry to say that you are probably better off having the tree removed based on what you have told me.

Q: I don't want suckering plants that are hard to control. Will Hansen's bush cherries sucker? I haven't found anything on the Web that specifically addresses this issue. I've planted two Montmorency cherries and two North Star cherries. Thanks to your Web pages, I just returned two Canada red chokecherries because of the terrible time many people seem to have with black knot disease. However, with two different types of sour cherries and with the potential for me to also plant another prunus in the Hansen's bush cherry, will the density of the prunus species make them more at risk for diseases such as black knot? We're in a new housing development, so there are not many trees. (e-mail reference)

A: I don't think you have to worry about the Hansen bush cherry. All cherries will sucker if given the opportunity. That opportunity comes from being planted too deeply, excessively pruned or physically damaged. As for the black knot, you should be safe for about the next 10 to 20 years until the population builds up in your development. Black knot can be controlled pre-emptively with fungicidal sprays, such as a Bordeaux mixture or Funginex.

Q: We were with a friend who wondered how the Bing cherry got its name. Please share the answer with us. I’ll see her next weekend and definitely will let her know and about seven others! (e-mail reference)

A: Seth Luelling was a skilled horticulturist. In the late 1860s, Seth cultivated the Bing variety notable for its large, firm fruit and sweet flavor. He named it Bing after his 6-foot-tall Manchurian foreman and close friend. Bing worked with Seth for 35 years until his contract was fulfilled and he returned to China. Bing cherries continue to this day to be the preferred fresh market cherry. If anybody is baking pies using Bing cherries, I’ll be glad to take one and sample it.

Q: I transplanted a sand cherry bush. It probably was the wrong time of year to do so, but I needed it moved. I did the same thing to this bush two years ago. The roots stayed active and a new bush evolved. Can I do anything to kill the roots? Will the roots of perennials eventually penetrate into my concrete foundation? (e-mail reference)

A: The roots won’t penetrate the foundation unless they are “superroots!” As to the roots regenerating a new shrub, if you see new sprouts coming up, spray or paint them with Roundup.

Q: I recently took down a Canadian cherry tree that had black knot. I left about a 12-inch stump. What is the best way to remove the stump? I would like to plant over that area again. Should I let it rot out? (e-mail reference)

A: You can rent a stump grinder and grind the stump and adjacent roots down to sawdust. Remove most of the sawdust and replant. Waiting for it to rot takes too long.

Q: I recently purchased a Canada red cherry tree while visiting North Dakota. The nursery never mentioned the fungus that you described in your column. They did mention the suckering problem that you described. While doing research on this tree and reading your comments, I discovered that I may not be doing my neighbors here in the state of Washington a favor by planting this tree because of the abundance of cherry trees here (both commercial and ornamental). I would like to get your opinion on this matter. I certainly would not hesitate destroying the cherry tree before it spreads the fungus to other trees. Could I plant a flowering crab such as spring snow instead? (e-mail reference)

A: You can take protective steps in controlling the disease with annual spraying. I am sure the specimen that you transported to your region is very likely disease-free. However, unless I had a passion for chokecherry fruit in the form of wine or jelly, I would go for the spring snow, which is a fruitless crab and has very beautiful flowers in the spring.

Q: I planted two Canadian red cherry trees around Memorial Day. They seemed to be doing great until about a month ago when one of the tree’s leaves turned brown and shriveled. The other tree was doing wonderful until about a week ago. The trees appear to be alive because the branches are not brittle. I have been watering them a great deal on the advice of the nursery. I just planted a third tree and I’m a little worried that I may lose it as well. Will these trees come back next spring? Our soil is mostly clay. Could this be the problem? Should I have cut off the burlap from around the ball? The nursery worker told me to leave it. (e-mail reference)

A: Pull the burlap back from the top of the ball and recover with topsoil. Make sure the twine is cut from the trunk. Also, stop watering so much. Clay soil holds water very well.

Q: I have three well-established nanking cherry trees. I want to plant them in a different area because they have taken over the spot they are currently in. Would I kill them if I transplanted them? How do I save them? They are 3-years-old, and this is the first year they have had fruit. (e-mail reference)

A: Wait until they go dormant this fall or do it next spring before they leaf-out.

Q: I know someone that would like to replace some Canadian red cherry trees. The trees are on the boulevard in front of the house. She has access to spring snow crab and royalty crab but she does not want a messy tree with a lot of fruit. (Minnewaukan, N.D.)

A: The spring snow crab is what she wants. This is a tree that does not bear fruit and is not messy. The bright, white flowers are knockouts as well.

Q: My neighbor dug out a Canadian cherry tree, but the roots are still growing into my garden and lawn. How can I kill them? (Jamestown, N.D.)

A: Treat them as dicot perennial weeds. Spray them with TRIMEC. You may have to spray more than once.

Q: My neighbor has some trees in his front yard that he calls Canadian cherry trees. They were planted two to three years ago and are approximately 10 feet tall. For the past few summers he has noticed a peculiar growth on some of the branches. They can get up to six inches long along the branches. Sometimes they drape all the way around the branches. He has been removing the affected branches but is wondering if this is the best way to treat the problem. (E-mail reference)

A: These are most likely Canadian red cherry trees. They are very subject to black knot, a fungal canker that can greatly disfigure a tree and eventually kill it. Removal and a vigorous spray program is advised. Removing affected branches won't often work because black knot is quite virulent and unrelenting in its spread. The fight is usually valiant but the tree owner invariably ends up the loser. He may want to capitulate and take the trees out now. The situation is only going to get worse with time.

Q: Are the berries of the Canada red cherry edible? I have loads of the beautiful red berries on my three trees. (Vergas, Minn.)

A: If you mean edible as in not being poisonous, yes. Eating them out of hand like Bing cherries, no. They make excellent jelly and jam and, I am told, good wine.

Q: Last summer we cut down my red Canadian cherry tree and now there are shoots coming out. Some of these shoots are 3 to 4 feet tall. I thought I would just leave them and see what it does but I just checked and it is full of worms. They are thick on there and have eaten all the leaves off some of the shoots. I did spray with Raid as it was the quickest and easiest thing to spray with at the time. What do I do now? Will these worms invade any other trees or shrubs? What do you suggest? (Tappan, N.D.)

A: The "worms" you are referring to are likely canker worms ( Paleocrita vernata) or a similar species that are tree defoliators, with apples and cherries being among their favorite to feed upon. The population peaks, then levels off to almost being unnoticeable for a few years before building back up again. Healthy plant material can tolerate a defoliation or two, but nothing more. Spraying (malathion, Sevin, etc.) will give partial control, but the ones that are missed or survive the spraying may live on to reproduce more resistant characters in future years.

Generally they are pretty host specific and will not move too far from where they are. They will go through a metamorphosis and emerge as either adult males or females to continue the cycle again next spring. Be careful spraying with pressurized insecticides. The carrier could cause physical damage to the plants. Actually, there is a product on the market that would be better (for both you and the plant, but not the insect!) sold under the Schultz product line, called Fungicide 3, which uses Neem oil, a natural product from the Neem tree, which kills all kinds of chewing insects, controls many fungal diseases, and acts as a miticide as well. It should be available in most stores that sell garden products. Rather than being pressurized with a carrier, it is in a pump container that is easily used.

Q: Three tears ago I planted Nanking cherries. They seem to be at a standstill. There are some that are now about 4 feet tall. They have never flowered. The rest are only about 1 1/2 feet tall. I do have a tin can around the base that I use for watering. Would this be hindering growth? When the taller ones got so far along I took the can off before I couldn't get it over the branches. (New England, N.D.)

A: I doubt the tin cans would have a negative impact on the plants, unless they were so pushed into the ground that they did some damage to the crown and some roots. However, I would still remove them this spring and see if you get the growth response you are looking for. If they show no inclination to take off and grow this summer, then the root system has been damaged some where along the line and they are not likely to make vigorous specimens.

Q: Could you please tell me what you think of Lapins cherry trees, or Bali? Are they a good choice or is there a better tree that could be used for pies and maybe fresh eating? I have two Northstar cherry trees. They really are leggy and put out only a cup of cherries or so; they are healthy but just don't grow. The idea is to replace them, unless you know of a way to make them really produce. (Fargo, N.D.)

A: These are cherries that originated from Alberta, Canada, with cold hardiness reported down into the minus 40s. They are not a sweet cherry, but are tart ones, with fruit getting about 1 inch across, ripening in late August. Unless you like eating tart cherries, I would say they would make good pies. They are also considered self-fertile, not needing another species for cross-pollination.

This information is all from Canadian data, so I would recommend these trees for trial purposes only. We do not have any local data on them.

Q: I have a Canada red cherry tree that gets growths on the branches. I have noticed a couple of others around town that also have them. I would like to know what is causing these growths and what I should do, and if they are threatening the health of my tree. (Ray, N.D.)

A: The fungal growth you are seeing on your cherry tree is black knot. Basically, pruning out and destroying the infected branches and spraying the tree with a product called Cavalier will control the disease in early stages, but if the infection is too bad, complete tree removal is the only answer. Because of the widespread nature of this disease, I no longer recommend planting the species in our region.

Q: We are planning some "garden" work in our new yard, and I would like to do things right the first time so I don't have to redo it later. So, I have some questions for you:

1.Is the Hansen's variety of bush cherries recommended for this area? I found that Nanking cherries are, but I couldn't find any information about the Hansen variety. 2.Is there a way that you can split and transplant a raspberry plant to increase your number of plants without buying more separately? 3.Are there different varieties of the chokecherry? If there are, which varieties do you recommend for this area? (Forman, N.D., e-mail)

A: The Hansen's cherry is not recommended for our area, as far as I can find out, but the sand cherry is.

Raspberries spread by underground runners known as rhizomes. They split easily and can be transplanted to new locations Do this in the early spring just before new growth shows.

All the chokecherries (Prunus virginiana) will do well in our region of the country, but they all sucker, so plant them where suckering is desired such as in a windbreak. If you can't tolerate suckering but want to plant anyway, do something to keep the root system confined so that the suckering can be controlled easier. The Copper Schubert and Boughen's Chokeless produce large, non-astringent fruits. Robert and Mini-Schubert are smaller, more compact plants with large red fruits that may fit into a residential landscape better, but these varieties will be more difficult to locate.

Q: Can you tell me if black cherry fruit is okay to eat? (Ellendale, N.D.)

A: Black cherry fruit is edible. Just don't eat the pits, branches, or leaves on this or any other Prunus species. And, like many of the others, it does make good jelly and wine.

Q: I need some help with a Canadian Red cherry tree in my yard. I noticed black knot for the first time this winter. I removed all the knots in March. I removed about twice as many branches this week. They were fresh knots. The tree is about 5 years old, and if I should abandon ship, I would like to do it now and plant an apple tree in its place. If there is some hope of stopping this disease then I would like to try. (Ypsilanti, N.D.)

A: Abandon ship! You will be doing the environment a favor by removing another vector of this disfiguring disease. I suggest a Honeycrisp apple.

Q: My Montmorency cherries bloomed erratically this year. On one tree with three trunks one trunk has delayed blooming and leaf production. It is not completely dead but very far behind the rest of the tree. A large plum tree 20 feet away has a problem consisting of tiny green tubes growing on the bottoms of the leaves. The other cherry tree has several branches that are not blooming also. Can I save them, and how? ( Bismarck, N.D.)

A: It doesn't sound too hopeful. The one tree with the delayed blooming is a sign of possible partial death of some of the feeder roots or a canker developing on the tree. The mere lack of blooming does not signify necessarily anything more than the buds possibly being zapped by the cold this past winter. The one with the best hope of surviving is the one with the green tubes on the bottom of the leaves. That is simply a gall that is cosmetic, not lethal.

Q: Should I spray my fruit trees with any kind of spray at this time? They are plum, apple, cherry, apricot etc. Also I have an apple tree with yellow delicious apples, but lost the name of the tree. Is there any way to identify it and what would you need to identify it? (Hague, N.D., e-mail)

A: All the spraying is done in the early spring or late winter, prior to leaf-out. I suggest a lime-sulfur and dormant-oil spray at that time--these take care of most overwintering insects and diseases.

If you have an apple tree with yellow delicious apples on it, then that is the name of the tree. I do not try to identify apples any longer. It turns out to be too much of a good guess or worse, a shot in the dark!

Q: We have Nanking and Hansen bush cherries and they blossom well, but they don't bear any fruit. What is wrong with them? I love your column and I always learn something new. (Groton, S.D., e-mail)

A: Could be several reasons: Cherries are early to flower and could be doing so when there were high winds, low temperatures or rainy periods so that the pollinators could not work. They could also be victims of selective frost or low temperature periods just when the stigma was ripe to receive the pollen. In the prairie states, the predictable, dependable, uniform pollination of fruit trees generally is not to be assumed or expected. We should be happy with what we get, if anything at all!

Q: Can you tell me what the enclosed growths are on my Canada Red Cherry tree and what I should spray to get rid of them? Also, should I take the tree down, will it spread to my other trees? (Detroit Lakes, Minn.)

A: First, one word answers your questions: yes.

1.Spray any trees with a light infection of this fungus, known as black knot, ASAP, again at petal fall, and shuck fall, with lime sulfur or tribasic copper sulfate.
2.Get rid of the tree—burn it if possible.
3.This fungus has become so wide spread on cherry and plum trees that I have difficulty suggesting them any longer for landscapes.

Q: The enclosed twig is from one of our three Canada red cherry trees. All of them have this fungus attached to them. Could you tell me what it is and what to do to get rid of it? (Felton, Minn.)

A: Thanks for the excellent sample of Apiosporina morbosa, black knot fungus. These knots eventually girdle and kill the branches. The infection perpetuates itself in the spring during periods of rainy weather. To control, prune out all visible knots immediately and spray the tree with lime sulfur if the buds have not already opened. After bud-break, spray the tree with a Captan/benomyl mixture.

An additional note: This is a very destructive disease often disfiguring the tree to the point of aesthetic liability. You might be better off in the long run, to take this tree out and replant with something else. I've seen too many cases where control attempts turn out to be a losing battle.

Q: Do you recommend growing Canada red cherry pruned like a tree or left unpruned to grow like a bush? (Leeds, N.D.)

A: Life would be a lot easier for you if you could accept it as a shrub.

Q: I thought I was planting ground cherries, but this is what I got. I can't seem to get rid of it! What kind of weed is it and how do I get rid of it? (Gary, S.D.)

A: I'm sorry, but I cannot identify this weed. I have asked a few others, but they don't have an answer for me either. Destroy the weed with Roundup before it goes to seed and spreads any further, and hopefully next time you plant you will get ground cherries. Thanks for the great sample!

Q: Can you tell me what kind of bush the enclosed leaves and seeds are from? They are really beautiful in the fall, and we would like to plant some in our yard. I would also like information on Amur maple trees and Canadian red cherry trees. (Garrison, N.D.)

A: It's a small irony that you requested information on a tree you wanted identified, the Amur maple—Acer ginnala. I have one in my back yard by the patio and I love it!

Q: Can you tell me what the enclosed white stuff is that is growing up my 10-year-old North Star cherry tree? The tree has been basically healthy, except for eight years ago when our dog scraped up the bark with a chain. Will the tree survive? (Willow City, N.D.)

A: Thank you for the good description of the injury that occurred to your tree eight years ago.

What you have on your tree is a wood-rot or decaying fungus—that may or may not form a canker girdling your tree. You can remove this organism by surgical means (carefully, with a pocket knife) and do whatever you can via cultural practices (fertilize, water etc.) to improve the tree's vigor.

Q: Enclosed I've sent what I call black grapes. Is this what they are and can we grow them in central South Dakota? Also, can bing cherries be grown here? (Midland, S.D.)  

A: Assuming you don't have severe exposure problems, I would say yes to both questions. Check with a local nursery to be sure. Thanks for writing.

Q: Enclosed is a limb off my Canadian cherry tree. I had the top trimmed off recently and there were several of the branches with this growth on them. We looked the tree over carefully and think they have all been removed. The tree looks healthy and is full of blossoms. It was planted six years ago. (Mayville, N.D.)

A: This is an outstanding example of black knot fungus that has been running almost rampant in our region over the past few years. High moisture and wind conditions are the primary reason for the spread of this disease.

The fungus can enter healthy or injured plant tissue, girdling the trunk and killing it. As the disease progresses the tree quickly loses any landscape appeal due to the grotesque shape it assumes.

Remove and destroy all infected wood by burning. Spray the tree with lime sulfur prior to bud break, and with Captain or Bourdeaux mixture after leaf-out.

Once started, this is a difficult, if not impossible, disease to control. If you live in the country where wild cherries surround your property, you should work on eliminating those plants as they serve as vectors for infection of our cultivated species.

Q. I had a question about black knot on Canadian Red Cherry trees. You suggested prune: prune them at the base. You were absolutely right; no matter what we've tried, the black knot comes back. The trees are coming out.

The trees were twelve in number, planted for an accent color around a circular flower bed at a cemetery. I don't know what we can put in place of the red cherry.

Thank you for continuing to answer our questions. (Litchville,N.D.)

A. Thank you for writing and the nice comments concerning my advice.

There are a couple of crabapples you may want to consider as replacement. One is Prairifire, gets about 15 to 20 feet high, has purple foliage when new, red-pink flowers, and dark red fruit. Another is Red Barron, which has a more columnar shape, with the same basic flower, fruit and foliage character. Both are disease resistant.

Q. I have enclosed a branch off a Canadian red cherry. What is the growth on it and can it be cured? Thank you. (Cooperstown, N.D.)

A. Your cherry tree has a fungal disease known as black knot. The most important thing you can do is remove and destroy all affected branches.

Lime sulfur is a good general control, as is Bordeaux mixture. Both should be available at the local garden supply stores.

If you live on a farm with either a shelterbelt or wooded area, check around the perimeter of your property to see if there are wild chokecherries or other species of prunus growing. They are usually the source of infection. Get them removed and burned ASAP.

Q: We have a Canadian red cherry tree that is very healthy. Underneath the tree are all sorts of sucker roots that come to the surface and begin to sprout. I cut them
with the mower every time I mow, but they are a real bother and very uncomfortable to walk on. Is there anything we can do to eliminate these roots without hurting
the tree? (Bloomington, Minn., e-mail)

A: If I knew, I'd be a millionaire! That is a typical characteristic of this tree species, unfortunately. Concrete, blacktop or a very big bed covered with
impervious plastic and covered with bark mulch 3 inches thick are the only ways I know of to keep the suckers from coming up.

My only suggestion is to remove the tree. Even then, you will have two to three years of fighting suckers from the roots that were left behind. Because
of this, I have a hard time recommending this tree for anything but shelterbelt situations.

Q: I visited your website today, and am writing in the hope you will respond (even though I'm not from North Dakota). I live in Eastern Canada and have two
Japanese ornamental cherry trees which are about 15 years old. For the last four or five years, both trees come out looking very healthy in the Spring, but within a
month or two the leaves start turning brown/yellow and falling. While there are still healthy leaves on the trees, they have been substantially defoliated.

The condition seems to occur whether there has been little rain or copious amounts of rain, so I don't think that is a consideration. Can you shed some light on this?

A: No problem. I just returned from a trip to Canada myself - Saskatoon, to be exact. There is a disease in the eastern part of North America that
resembles your rough description of what is happening to your trees. A fungus known as cherry leaf spot (Coccomyces hiemalis). Once infected, the
re-infection can occur from leaf debris remaining from the previous season quite easily. The first step in controlling the disease is to rake up and destroy
all fallen leaves this autumn. Spray the tree the following spring with lime-sulfur, a good, common surface sanitizer, while the tree is still dormant. After
leaf-out and when the petals flower petals fall, spray with a fungicide containing captan or chlorothalonil. Respray twice more at 10-14 day intervals.
This treatment should put this disease or any fungus disease in check.

Q: I have Nanking cherry bushes that are 3 years old and 5 to 6 feet tall. I don't want them any taller. Can I trim them as a hedge, and when would be the best time to do so? Also, how might I keep lambsquarter and kochia out of the strawberries? I have a huge patch and can't get it all pulled. (E-mail reference, Aberdeen, S.D.)

A: Yes, the Nanking cherry can be pruned as a hedge. It tends to open and spreading in the natural state, so the pruning would likely help to thicken the growth somewhat. Best time is in the early spring before leafout. To control broadleaves in stawberries, I suggest looking into Dacthal, Devrinol, or Princep.

Q: I have a Canadian Red Cherry tree that has black growths all over it. At first I could cut off a few each year, but this year there must be 100 or more. Is there a cure? I hate to destroy the tree. (Rogers, N.D.)

A: Not likely at this stage of infection. You are better off removing the tree completely to keep it from being an infectious source to other trees in the area.

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