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Ron Smith answers questions about flowers, trees, gardens and shrubs.

By Ron Smith, Horticulturist

NDSU Extension Service

Q: My husband and I are interested in planting a bloodgood maple or a thundercloud plum because we need a tree with a shallow root system. Which tree would be best? (email reference)

A: For just those criteria alone, the maple would be best. It is a cultivar of the Japanese maple, which is known for its ornamental value and has shallow roots, compared with other maple species.

Q: I wrote you last fall about some crabapple trees growing near my house. You were very helpful, so I thought I would give you an update. I cut down two seckle pear trees in my backyard early this spring to make room for a crabapple tree. The pear trees were nice trees, but the gray squirrels have taken all the pears every year. I still have a sugar pear tree in my front yard. I planted a dolgo crabapple tree where the pear trees used to be. The tree is nicely shaped and has green buds on all the branches. What I'm curious about is how long it will take before it starts bearing fruit. Last fall, I made 15 gallons of crabapple wine from two trees near the local Subway restaurant a couple of blocks southeast of my house and another 15 gallons from three trees in the city park a couple of blocks northwest of my house. I drank some of the Subway wine last weekend. It is very light in color and has a very mild flavor. I haven't had any of the city park wine, but it is much redder, so I'm sure the flavor will be stronger. I really wish I knew what variety these crabapples are. (Plainfield, Ill.)

A: Thanks for the update! The dolgo is a very productive tree. With a little luck, you should start seeing a limited number of apples on it next summer. That should be the start of an avalanche of apples every year thereafter. I will not be surprised if, in about five years, you were to email me and say that the tree is bearing too many apples for you. It will make a delicious wine, so enjoy.

Q: I have a garlic grower client who has a garden near a river. His garden has been underwater for 11 days. The ground was frozen when it flooded. The grower is wondering if his garlic has a chance to survive. (email reference)

A: I wish with all my heart that I could say yes, but I seriously doubt the garlic will survive. If it does, I would like to know. One of the criteria for growing good garlic is excellent drainage, so being entombed in frozen water that long would seem to spell death. I would suggest digging a few samples as soon as the water recedes to see if there is any life remaining.

Q: I have a problem with my umbrella plant. I’ve had to place stakes for it to stand straight because it is so tall. I turned it around because one side was getting more sun. At first, it did OK when I turned it, but now the bigger leaves are curling. I fed it a couple of aspirin in warm water to help it about two weeks ago, but that didn’t work. Is there something I can do to help it come back? (Bloomfield, Mich.)

A: This sounds like an insect problem. Examine the plant carefully to see if there are any signs of small webbing (spider mite infestation) or small bumps on the underside of the curling leaves, leaf petioles or stems. This would be indicative of a scale infestation. In either case, if the infestation is bad, you would be better off dumping the plant and starting over. In fact, from what you have told me, it probably would be a good idea to do that anyway rather than fighting what sounds like a losing battle. If no insects are found, as a last, desperate measure to save it, you might try repotting it in a new container using potting soil purchased from a local garden center.

Q: We have two 3-year-old silver maples. One is in front of the house, while the other is in the backyard. The backyard tree seems to be doing well, except half of the top looks dead. The one in the front is perfect. What can we do to help the problem tree grow leaves on top? (email reference) A: Try to determine why the top part of the tree is dead. This could be from a canker disease that has partially or completely girdled the stem. The problem also could be borers or bark beetles. Contact the Extension agent where you live to come out and examine the tree. If you don’t know who the agent is, go to and click on your county to get the name.

Q: I live in Texas and I am growing onions for the first time. I planted them in late February. There are seeds growing on top of each onion. What should I do with the seeds? (email reference)

A: I don’t know anything about growing onions in Texas, so I can’t advise you. You can contact the Extension agent in your county for an answer. Go to to find your Extension agent’s phone number. If the agent can’t provide an answer, he or she can get you hooked up with a horticulturist at Texas A and M who can.

Q: The peace lily I have had for years suddenly is looking ill. When I watered it the first time after fertilizing, I noticed the water draining out of the bottom was rusty red. This never has happened before. Can you help? (email reference)

A: All I can guess is the plant is responding to too much fertilizer. The high salt concentration would cause wilting to take place. I would suggest a couple of more flush waterings to see if that helps improve the situation. If not, then the plant probably has a rot problem and is doomed.

Q: How far does bald cypress need to be planted away from a basement to keep the roots from causing damage? Thank you. (email reference)

A: You had better figure on a 40-foot distance to be on the safe side. Of course, in a landscape situation, it probably wouldn’t be that much because I am assuming that you wouldn’t be placing it in a swampy situation to develop the “cypress knees” that are hallmarks of this species in such a setting. This kind of spread would be something found in nature on a mature, 60- to 100-year-old tree. However, at that distance, I doubt the tree would cause any damage to a solid basement wall.

Q: I love your website. I live in Rhode Island near a bay and have a patio that needs a privacy screen. The many deer in the area ate my arborvitaes, so I need to rethink what to plant. We also are in the path of nor'easter winds. Do you have a recommendation for a privacy screen that would not get taller than 7 to 10 feet and less than 4 feet wide? (email reference)

A: This is a tough recommendation to make because deer will graze on just about any plant material if they are desperate for food. Physical screening is about the only dependable thing we can use in the Midwest. Everything else works, but only up to a point. When that point is reached, then anything is fair game. You should contact someone in the Connecticut Extension Service to assist you in this undertaking. Go to for contact information. Thank you for your very kind words about the website. It is appreciated.

Q: I planted two shumard red oak and two red maple trees in a row spaced 40 feet apart. I just purchased three eastern redbud trees that I would like to plant between the red oak and red maple trees. I know that I can keep the redbud trees pruned enough so they won’t get very large. Will my plan work? (email reference)

A: I cannot think of a good reason why you shouldn’t go ahead with the planting. Keep in mind that, in a natural environment, the redbud is a subcanopy or edge canopy species, so they should do well in the kind of setting you have in mind.

Q: Do you know where I might find the zinc phosphide you mention on your website? I checked several location, but didn't find it. I did pick up some Sweeney Poison Peanuts to see if it will do anything. This year, the voles have completely taken over my backyard, so I would sure like to get rid of them. Rabbits also did their nasty work this winter by eating the bark around my snow crab. I'm sure it will be dead. (email reference)

A: You’d probably have to go online to get zinc phosphate. However, the poison peanuts should do the trick. As you find the dead bodies, bury them so they are not eaten by birds of prey or neighborhood cats and dogs.

Q: I have a huge Canada cherry tree in my front yard that has black knot. I suspect it needs to be trimmed and perhaps treated. I’ve heard the fungus eventually will kill the tree. It also might kill me because I love that tree. The affected areas on the tree have increased from last year. Can you help me or suggest someone who can? Thanks. (email reference)

A: While black knot usually ends up directly or indirectly killing a tree, it doesn’t have to be that way if you can catch it early enough and provide some control efforts. Get the affected branches removed. Cut the branches back at least 6 inches from the point of infection. As the buds are beginning to swell, but before they open, spray the entire tree with lime sulfur. After the blossoms drop, spray again with an all-purpose fungicide. Be sure black knot is listed on the label. Reapply according to label directions through the season. Also, scout your property edges to see if there are any wild or unwanted cherry species that are harboring the fungus. If there are, get rid of them.

Q: Is it common to plant cutleaf weeping birch in a tight clump? I like the look, but I mostly see it done with European white birch. I have three weeping birch trees in pots that I want to plant in a clump. I just wanted to check if there was a reason for not planting this particular birch in a clump. I like the look of the cutleaf weeping birch, but it does not have real thick foliage. That is why I was going to plant this clump so when it matures, it blocks or breaks up the setting sun from shinning in our living area. Any advice will be appreciated. (email reference)

A: There is no reason why you cannot clump the three birches together to form a massive canopy and shady environment. I have a cutleaf weeping birch in my front yard. I have to say the canopy is not sparse! It has been there for 25-plus years and has provided us enclosure and shade for the last 20 or more years. My wife and I simple love the tree for all that it does for our home. Plant the trees tightly in the same hole so the roots will graft together to become a single unit. Generally, this is done when the trees are younger so you get a tighter clump effect.

Q: My wife purchased tulips from a local store. The tulips are about to open and blossom. We will use them as centerpieces for our Easter dinner. Can we plant them in the garden after Easter? We live in hardiness zone 5. (email reference)

A: Go ahead and plant them in their entirety to keep from disturbing the roots too much. When the foliage dies down in May or early June, carefully dig out the bulbs and place them in cool place, such as the crisper drawer of your refrigerator, until fall (mid to late October in your zone). This will assure sufficient chilling to get them to bloom again for you next spring.

Q: Now that the snow is gone, I can see that our lawn is a disaster. It looks like something has been digging it up. The whole lawn is covered with holes about 2 inches in diameter. Any suggestions would help. Thank you. (Big Detroit Lake, Minn.)

A: Not to worry because this is normal after the winter we just went through. A standard lawn cleanup/light renovation will clear everything up quickly. When the soil is dry enough so that you are not leaving a wet footprint, you can begin with a light power raking. After that, fertilize and apply a grub insecticide such as Sevin. Be sure to follow label directions. If the mounds reappear in early to midsummer, reapply the insecticide. The damage you see likely is caused by night crawlers that are beginning to become active now that the frost is leaving the ground.

To contact Ron Smith for answers to your questions, write to Ron Smith, NDSU Department of Plant Sciences, Dept. 7670, Box 6050, Fargo, ND 58108-6050 or e-mail

NDSU Agriculture Communication

Source:Ron Smith, (701) 231-7123,
Editor:Rich Mattern, (701) 231-6136,
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