Questions on: Dogwood
Ron Smith, Horticulturist, NDSU Extension Service
Q: I have a pink dogwood in my front yard that has few blossoms. It needs a bit of pruning to remove some dead branches, but nothing major. The leaves look healthy and it has good coverage. Is there anything I can do to increase the blossoms next year? (e-mail reference)
A: The sparse blooms this year could be weather-related and nothing more. Basic care is all that is needed. Dogwoods like acid soil, so look for fertilizers that are meant to acidify the soil.
Q: I was about to plunk down hard-earned cash for a dogwood fertilizing kit when I spied your Web site. We live in Virginia on a dogwood-lined street. We planted five in front of the house two years ago. One is at the drip edge of a linden tree. Its leaves are sparser than the others. Is it stressed for water or in need of fertilizing? Is it doomed? Thank you for your advice. (e-mail reference)
A: Dogwoods are subcanopy trees that thrive along the edges of wooded lots or forest stands. The linden is a very densely leafed tree when it has a full canopy, so it might be that the tree is casting solid shade. Dogwoods do best in dappled shade or full sun. I believe that the problem probably is water and nutrient competition from the linden or the roots are exuding an allelopathic substance that is inhibiting the growth of the dogwood. I would try some extra fertilizer and water to see if the tree can be knocked out of this funk. Otherwise, I don't know what else to suggest.
Q: We built our home in a wooded area two years ago. I was careful to save a dogwood tree in the front yard. The tree seems to be doing well. It leafs out every year and it gets the green berry flower center, but it isn't producing the white, flowery leaves around this center berry/flower. We have a dogwood identical to it down the street that is flowering properly. Is there anything I can do to help it flower? I am worried that maybe we cleared too many trees around it. (e-mail reference)
A: The dogwood "flower" that everyone refers to is actually a series of modified leaves known as bracts. They color up about the same as poinsettia "flowers" do. The actual flower is in the center of these colorful bracts on both species. While long nights initiate flowering and bract coloring with poinsettias, I'm not sure what turns the bracts white on dogwoods. I would encourage you to be patient because it should recover.
Q: We moved into a new home with a small dogwood tree in the backyard. The tree was planted by the previous owners along the south side of a north-facing fence that receives the full brunt of heat and sun during the summer months. Last summer it was very dry, so the leaves curled, dried and fell off. Can I transplant the tree to a shadier area on the north side of the house this spring or do I need to wait until after the first frost? (e-mail reference)
A: If the tree is dormant at this stage, transplant it. Wait if the tree is not dormant. Try to keep the tree's root system moist (not soggy) and cool by using an organic mulch.
Q: I believe my dogwood is not coming back to life this year because there are ants in the soil. Do you have any suggestions to help me? (e-mail reference)
A: I don't have an answer based on the information you gave me. However, I can almost assure you that the ants are not the direct cause of your problem.
Q: We have a dogwood in our backyard that was beautiful two years ago when we moved in. About a year ago, the neighbors had a pine tree cut down that was very near our dogwood. Part of the pine tree fell and broke one of the biggest branches of the dogwood. We made a clean cut where the break occurred, but since then the tree has been in distress and other branches have been dying. Now, at the beginning of spring, only one branch has flower buds. What should be done? Is there any hope of our dogwood surviving? Additionally, we have six dogwoods in the front yard that are full of buds, except one. There has been no known damage to the tree. What could be wrong? Any advice you could give me would be very much appreciated! (e-mail reference)
A: There is no hope for the dogwood that was damaged by the falling pine branch. The problem with the tree that is not budding could be borer damage, stem cankers, root rot organisms, an abiotic cause of death, girdling by rodents, a saturated root zone or environmental exposure. Only a close inspection by someone knowledgeable about plants can determine the actual problem.
Q: I have a dogwood tree that my mother planted about 10 years ago. The tree is not doing well. It seems to have stopped growing. The bark is split at the base of the tree and there are small holes where the bark is missing. The bark on the tree also doesn't look good. My mother planted the tree years ago. She has passed away, so I really don't want to loose the tree. I hope it's not borer or canker. Please help me. (e-mail reference)
A: The tree looks like it is beyond help. Sorry! From what I can see, the tree was sited improperly when it was planted. Generally, these trees don't do well in an open, fully-exposed environment such as yours. In their natural environment, they are a subcanopy species or found on the edge of a forest. You might consider hiring a certified arborist to inspect the tree. It may be possible to rehab the tree, but I would be surprised if someone had a concrete solution to the many problems this tree appears to have. Go to http://www.treesaregood.com/ and click on "Find A Tree Care Service" at the top right side of the page to find a certified arborist.
A: Prune to your heart’s content. You could prune it back to the ground with all of the branches. It will surge with a flush of growth this spring that you can shape to your liking.
Q: We have a hedge of dogwoods that are overgrown, so we need to prune them to the ground. Can we do it this fall or should we wait until spring? Also, I need to move some rhubarb. Can I do that this fall or is it advisable to wait until spring? What kind of soil amendments should we use? I have a morden sunset rose that had a bad case of black spot this summer and now has very few leaves. Can I cut all the canes down to about 6 inches and clean up all the mulch and leaves or is it a lost cause? (Cooperstown, N.D.)
A: You can cut the hedge back in late fall or early spring, but before new growth begins. Fall usually is preferred because the working conditions are better. The same holds true for rhubarb. Always add sphagnum peat moss because it will never hurt and always helps. For your rose, do the cleanup and next year use a systemic fungicide to control black spot.
Q: I have a rather large dogwood in my backyard that is growing clusters of little, light-green berries. I also have a 1 1/2-year-old daughter who loves to pick them off. I am forever trying to make sure she doesn't eat them (I think a couple have made their way into her mouth). Are they poisonous? (e-mail reference)
A: They are not poisonous, but it is still a good idea to be vigilant because she could easily choke on a berry at that age.
Q: I have a white flowering dogwood. It had very heavy, beautiful blossoms, but when the leaves came out, they wilted. They were stunted as well. The tree gets ample water. I did two things differently this year that may have affected the tree. I put some Job fertilizer tree stakes in the ground in early spring, before the leaves came out, and sprayed the lawn with Weed-Be-Gon liquid weed killer. This also was done before the leaves came out. I was careful not to get the canopy wet, but I did spray the lawn under the tree and near the drip line. Could this have caused my problem, and do you think the tree will survive? (e-mail reference)
A: The fertilizer stakes are close to being useless. Research has shown that they do not provide significant benefits to trees or shrubs. Most trees and shrubs do not need supplemental fertilization unless they are in very poor soil. The herbicide is the likely culprit because flowering dogwoods are very sensitive to any kind of broadleaf herbicide. The active ingredient in Weed B-Gon (2,4-D) is mobile in the soil. The 2,4-D could have been taken up by the root system of the tree, resulting in the problems you are witnessing. As to whether the tree will survive, only time will tell. Just have a little patience.
Q: We are on our second snow mantle dogwood tree in four years. The tree starts out looking beautiful in the spring, but then the leaves curl and droop, producing a very unsightly tree. Is there any hope or should we find another species of tree to plant? The tree is in heavy, clay soil and is on a slope. We thought is was getting too much moisture, so we amended the soil and covered the area around it with plastic before replacing the rock to prevent excess moisture, but this has not helped. Any suggestions will be most appreciated. (Forest Lake, Minn.)
A: You are attempting to grow a tree that is not suited for the environment you are setting it in. Dogwood needs well-drained, high-organic soil, morning sun and no plastic or rock over the roots.
Q: I am from Charlotte, N.C., but now living in North Dakota. I would love to have a magnolia tree, but there is not enough love here in zones 2 and 3 to keep it warm and alive! I would like to inquire on the viability of a dogwood or cherry tree. How about wisteria? If you have any suggestions on any plants/shrubs/trees that are from the southern region that may work here, please pass them along. (Bismarck, N.D.)
A: What a change, from Charlotte to Bismarck! Welcome to our fine state, even if it isn't as warm as your former address. The pagoda dogwood might grow in Bismarck in a protected location. The recent introduction of the snow mantle dogwood by our woody plants researcher, Dale Herman, also may work for you. The chokecherry is the only tree form that can grow in North Dakota, but we are finding out that it is susceptible to black knot fungus, which debilitates the tree. Wisteria is too marginal to recommend for our region, but clematis vines do beautifully in most landscape situations. Go to www.ext.nodak.edu/extnews/hortiscope/tree/treecntnts.htm for a list of trees that you may want to consider.
Q: I have several variegated dogwood shrubs that I cut back about every three years. I have done it in the fall. Is it better to do it in the spring? (e-mail reference)
A: It makes little difference, but I believe the fall is easier because our spring weather is so fickle and often keeps us from getting out to do yard or field work as much as we would like. If you have done it this way in the past, there is no reason to change.
Q: We have a dogwood bush that is approximately 8 years old and stands about 4 1/2 feet tall. I would like to move it to another location in our yard. What type of roots do dogwoods have, can they withstand being cut to be moved and how deep are the roots? (e-mail reference)
A: Dogwoods are easy to move. If you can get to the bush right after a hard frost stops growth for the season, go ahead and cut it back and get the plant moved as soon as possible. Water it well at the new location and the plant should be all right, surging with new growth next spring.
Q: Is it possible to dig up small dogwood saplings and store them over the winter? If so, how would we do it so that we could replant them in the spring? Thanks for your help. We enjoy your column every week in the paper! (e-mail reference)
A: If you want to dig up the dogwood seedlings this fall, rather than early next spring, then wait until they have been hit by a couple of frosts. Thanks for being a loyal reader of the column!
Q: I have three variegated dogwood bushes on the north side of my house that are looking shaggy. Will it hurt to prune them this time of year? I have heard that you need to take special precautions when pruning because they are very susceptible to disease after pruning. What do I need to do? (e-mail reference)
A: Cut them back hard early next spring while they are still dormant.
Q: We have a 14-year-old dogwood. It had a mixture of reddish, flexible canes and brittle brown canes. We pulled out or cut down all the brittle canes. There is green at the base. Was this the right thing to do? In addition, do established lilac bushes do well after transplanting? (e-mail reference)
A: You did the right thing with your dogwood. Lilacs transplant well as long as they are not coming into leaf; so transplant lilacs while they are dormant.
Q: We planted two European strains of variegated dogwoods back in 1994. They’ve done well until the past few years. The leaves, which are variegated green/cream, would shrivel up, fall off and look terrible. Last fall, I got carried away and pruned both of them back to about 9 to10 inches. I hope I haven’t discouraged them from growing back. (Minot, N.D.)
A: You haven’t, so don’t worry. They should sprout and grow with a vengeance in a few weeks.
Q: I recently planted two dogwoods in my front yard. After three weeks, the leaves turned bright red and then died and fell off. The branches appear healthy (moist and flexible). Is there a possibility they will come back or should I replace them? (e-mail reference)
A: As long as there is a twinkling of life in the limbs, there is a chance that they will come back. Don’t overwater or fertilize.
Q: I have two large dogwoods. They are about 15 to 20 feet tall and 6 to 8 inches at the base.
Two months ago I did some landscaping and put dirt around the trees to a depth of about 4 inches. My plans were to let the dirt settle and then dig out dirt from the tree back about 4 or 5 feet to form a border. This would put the soil in the 5-foot ring back to the same depth as before. I did that a few days ago, but now I am noticing that the tree has white worm-looking tentacles coming off the base. They are about a half to three-quarter inch long. When you pinch one, it crumbles like dirt. Did I leave the dirt covering on too long? (e-mail reference)
A: It sounds like you stressed the tree and made it vulnerable to borer attack. What you saw was the borer larvae feeding on the cambial tissue. Dogwoods are very sensitive to having their roots covered. Even digging back as far as you did will not suffice. The roots spread way beyond the canopy. There is little you can do at this point except hope it recovers.
Q: Out of 40 dogwood trees, only one small group is having problems. Dark spots began appearing on the leaves within the last week. The leaves are now drying up and falling off. The trees are about 4-years-old. They are watered from a well and no pesticides have been used. (Dickinson, N.D.)
A: I don’t know what to recommend. It appears to be a fungal leaf spot disease of some sort. There is a plethora of problems with this species, so anything and everything is possible. Send a sample to the NDSU plant diagnostic lab for an accurate diagnosis and remedy.
Q: We have a dogwood hedge that is about 10-years-old. We do not want it to get any taller and we need to make it narrower because it is beginning to get in the way of cars on our driveway. Is there a proper time to prune it and how do I keep it trimmed? (Tyler, Minn.)
A: It is probably still early enough for you to do some selective pruning. Go right to the base of the plant and remove a third of the oldest canes. This will not destroy the aesthetics of your hedge.
Q: In late summer last year my variegated dogwood and an Engelman ivy vine began to look sickly. By fall the leaves became crisp and dried up, never taking on fall coloring. What should I do this year to avoid this from happening again? I’ve always found dogwood to be disease-free until now. (Carrington, N.D.)
A: Your plants never completely hardened off last fall. It could be due to excess rain, irrigation or high fertility levels. Try to avoid the latter two going into the fall and the plants should be alright.
Q: In my yard I have a variegated dogwood that is dying. The branches range from dead to healthy. Some branches have leaves that are turning brown while other leaves are very healthy. It resembles fireblight in apple where the bark tends to be reddish in color and shriveled up like an overdone summer sausage. I'm trimming out all the dead branches. (Mott, N.D.)
A: Unfortunately for all dogwood species, they play host to a plethora of disease organisms but fortunately fireblight is not one of them. If there is no evidence of sawdust around the base of the plant, then I would say, fairly safely, that your problem does not involve borer or stem girdler insects. My best guess is that the plant is suffering from one of the many stem cankers, probably downy mildew. You are correct in removing completely the stems that are showing symptoms. I would suggest adding a spray program to control the spread. Two fungicides come to mind, Banner (propiconazole) and Daconil 2787 (chlorothalonil). The first is a systemic that needs application only 14 or so days, especially in the beginning of the season. The later is a contact fungicide that should be applied weekly. I must emphasize that fungicide is effective at preventative control, not curative. Any applications you make this late in the summer will not have much of an effect but would be most useful next spring, assuming your plant makes it that far. The variegated form of dogwood shrubs are especially susceptible to stem cankers and leaf anthracnose. They all start out looking good as young plants but seem to spiral downward with age.
Q: We are moving to a new house this fall in West Fargo. I have several red twig dogwoods in my yard that I would like to take seed from and plant in our new yard this fall or next spring. In making a hedge, can I put down weed fabric protector and then rocks around them? Should I just buy new bushes next spring? (West Fargo, N.D.)
A: The easiest and least frustrating approach is to purchase some new shrubs next spring. The results will be quicker and you will be happier.
Q: Three years ago I planted two dogwood bushes of the ivory halo type. They were growing well and looking good until August of last year. One of the bushes turned a reddish color, had a few berries, then both bushes died. I could not see any bugs and the leaves didn't look like they were diseased. Any ideas why they died so suddenly? I didn't do anything different than I did in previous years. (Minneapolis, Minn.)
A: I could give you a half dozen guesses but that wouldn't help you. They simply could have been planted too deep which seems to be a common problem in the upper mid-western region of the country.
Q: We just planted a couple variegated dogwood bushes a few weeks ago in the front of our house (mostly shaded). The leaves are wilting on one of the bushes and the other is starting to. We've gotten plenty of rain -- the soil is damp. Any ideas? (Minneapolis, Minn.)
A: Transplant shock, perhaps. I assume they were guaranteed by the nursery. I would give them a few weeks to see if they pull out of the slump, and if they don't, take them back.
Q: I would like to find the "reddest" and tallest growing variety of red twig dogwood. We are not interested in long term trees, just tall straight trunks 7- to 9-feet high and turning red as possible in winter cold. (E-mail reference)
A: You can go either with Cornus alba, (Tatarian dogwood), which has bloodred twigs in summer, the C. stolonifera (redosier dogwood) with the same qualities, both being shrubs, or the Prunus maackii (Amur chokecherry), which is a small tree that has an attractive copper-colored, birch-like bark.
Q: I have a 3-year-old red twig dogwood tree that has never grown more than 14 feet tall. It starts growing from the ground each year in the spring. How can I get it to grow taller so it will bloom? Also, I planted a Redbud, a weeping willow, and a Ben Franklin tree this year. How can I protect them from the winter frost? Do they need to be protected? (Onida, S.D.)
A: The dogwood doesn’t like where it is planted. Replant it somewhere else. It never hurts to give fresh plantings protection through the first few winters. Wrap the trunks and make sure they go into winter well hydrated.
Q: The fern peonies here in town have now begun to brown and fall down. Can they be cut to the ground yet? I know the leaves of dandelions that currently are growing freeze over the winter, but do new shoots come from the existing plant next spring? In other words, is it of value to spray and kill the current plants to ward off them reappearing again in the spring? I have red twig dogwoods that have exploded out of control this summer. Beautiful, but drooping with new growth making for difficulty mowing under them. How does one deal with such ambitious growth? It seems to me that certain oaks at the farm produce way more acorns than other oaks of the same size. I think that there are some oaks that produce no acorns, but I could be wrong about that. Any thoughts on this? (Fertile, Minn., e-mail)
A: Cut down your peonies. Spray your dandelions. As for dealing with your dogwoods, the best method is to cut them back to make mowing easier. Not to worry, they are completely winter hardy and will not suffer from a late summer pruning. The other way, tying them up, is a band-aid approach and not very effective or pretty.
And, it is true that some oak trees are more fruitful than others. Sometimes the fruiting is related to the stress the trees are under, as well as the age. Older, stressed trees will tend to fruit heavier, while younger (but still mature enough) less stressed trees will go fruitless or bear very little fruit. Another reason could be hardiness. The flower bud is less hardy than the leaf bud. Hence, the oak that is marginal in hardiness may get caught in a late spring freeze that kills the flower bud, but doesn't harm the leaf bud.
Q: Can you tell me what is wrong with my dogwood? (Cando, N.D.)
A: The dogwood sample you sent had a good dose of anthracnose and botrytis—both fungal diseases brought on by wet springs. Clean up fallen leaf litter this autumn and spray next spring at leaf opening with Fore or Maneb.
Q: Enclosed are a couple of leaves from my dogwood shrub. Can you tell me what is eating them, and what to do to stop it? Also, if I prune my raspberries this fall, will they bear fruit next year? (Valley City, N.D.)
A: The damage appears to be that of a "garden variety" caterpillar that visited your dogwoods for a snack and are now beautiful butterflies!
I suggest no sprays at this time; next spring before leaf-out apply dormant oil to the shrubs to kill off any eggs the butterflies may have laid.
Raspberries bloom on second year wood (except the fall bloomers), so the canes that grew this summer should bear fruit next summer. Old canes that bare fruit this year should be pruned out completely.
Q. I've not written to you before, but I turn to your column before any other on Fridays when the Farmers' Forum arrives. May I ask a few questions, please?
(1) Do small evergreens like lots of water? I bought two small (about 1 foot high) bushes earlier this summer. I delayed transplanting the bushes, but they seemed to thrive and then suddenly both died. Someone told me I need to use Miracid on evergreens, but perhaps I bought the product too late. I did water the bushes a lot.
(2) I wonder why my 15- to 18-year old Bridal Wreath died back to the ground. It is a foundation planting and was huge and gorgeous until three years ago, when branches began to die. All branches are now dead, but new growth is coming from the ground. Should I use Miracid?
(3) My beautiful 12-year-old white old-fashioned lilac bush (about 9 feet tall) is dying. Several large branches have leaves that are totally withered and brown. I began to notice the withering about Aug. 1. Might I have overwatered?
(4) My dogwood bush looks rather sick, too. The leaves have strange spots on them.
(5) I have an old (about 25 years) phlox that flourished and produced beautiful rose-colored flowers until about four years ago. Now, it begins with green sprouts (in the spring) but fairly quickly the stacks become brown and shriveled. It does not get much sun.
I would appreciate any suggestions you might make. I'm hopeful you will continue your column. (Fargo, N.D.)
A. Oh, brother! Your questions could launch a thesis! I'll do my best to provide you with direct, accurate answers based on what you have told me.
1.Evergreens do not do well under continuously wet conditions. They are generally upland plants, able to survive extended waterless periods. You most likely killed them with too much kindness.
2, 3, & 4. Spireas should be pruned each spring to remove the oldest woody canes; lilacs are hosts to borers and scale insects, and at least a half dozen fungal diseases, any of which could be causing the symptoms you describe. Ditto for the dogwood.
5. A phlox plant that is 25 years old? That has to be a world record! Dig and divide, reset in sunny locations. I am surprised powdery mildew and spider mites didn't take their toll.
Fertilizing with Miracid or Miracle-Gro certainly won't hurt anything. While it will help plants along, it won't resurrect the dead ones.
Thanks for writing and for the nice comments.
Q: I see your column is still
going strong and it's still the
most informative horticultural site I've yet been able to find.
Anyway, I have a question. Last fall I bought a
reddish dogwood tree and planted it in the middle of our lawn under some sycamore trees. In summer, it gets about 1.5 hours of sun. Lately, it looks like the leaves,
what few there are, are burned. What could be the problem? For its first year, it didn't bloom much and now the leaves are burned at the ends, and many have
dropped off. Help! (E-mail reference, Lebec, Cal.)
A: It sounds like the dogwood is non-adapted to the site you selected to plant it in. Dogwoods, with few exceptions, like a loamy soil, rich in organic
matter and not a lot of push from fertilizers. If you have it planted in a lawn area, that could be the problem, as it should be "bedded" - that is,
incorporated in with other sub-canopy trees and shrubs. The red dogwood is more sensitive than the white to environments - soil, wind, humidity, etc. I
suggest you try again with a Cornus nuttallii, or the Pacific Coast Dogwood. It is native to your region of the country.
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