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

By Ron Smith, Horticulturist

NDSU Extension Service

Q: This fall, I had three somewhat decrepit ash trees cut down. A friend with a chainsaw cut a cross section so I could count the rings. How far out do the countable rings go? Do I count the rings in the cambium layer and/or the bark? We bought the lots with the trees growing on them in 1950. I count 69 rings if I only count the rings in the woody core. Some rings are much larger than others. I suppose I could match that up to our annual rainfall if I had the time, patience and statistics to do it. I'm not sure where I'd find annual rainfall records. (Cooperstown, N.D.)

A: Annual growth rings are difficult to count accurately but will give you a good approximation about the age of your trees. Growth rings are influenced a great deal by rainfall intensity and duration. We could have a very wet spring, which would result in a generous ring. However, a dry summer followed by a wet late summer or fall would give you another ring to be counted. For data on precipitation, I’d suggest contacting Adnan Akyuz, who is the state climatologist. He is very sharp and full of useful information that we in horticulture and forestry find quite helpful.

Q: I am looking for vermiculite for the square foot garden I plan to start next spring. I found vermiculite in the home insulation section of a store, but nothing in the garden section. Will vermiculite used for home insulation also work for gardening? (e-mail reference)

A: I don’t recommend the use of vermiculite for various reasons. It is too light in weight to provide a stable anchoring media for plant roots. Unless you can find certified asbestos-free vermiculite, you shouldn’t use it because of the obvious threat to respiratory health. Even if you do find certified vermiculite, there is mica dust that is generated from pouring it out of the bag. While a onetime exposure will not kill you, it should be avoided whenever possible. My wife and I have found that a good combination of sand, soil and generous amounts of sphagnum peat moss will deliver just as good of a garden crop.

Q: I planted a hybrid poplar in my yard about two or three years ago. This year, it spawned three suckers. I cut the tree down and started to dig out the stump. If I cut the roots about a foot from the stump, will that kill the roots or do I also need to apply herbicide? Someone told me the tree might be a dreaded Lombardy. If so, is Trimec the answer? (e-mail reference)

A: You probably will need to apply Trimec to the sucker growth that is likely to take place next spring even if the tree isn’t a Lombardy.

Q: What is the best way to protect for winter some new arborvitaes we planted? We planted them for privacy, which means they were planted along the southwestern corner and west side of the property line. I have read that those locations are the most vulnerable spots for trees to be planted. I also should note that we live on a lake where we get some strong winds. Some of these trees are elevated near a retaining wall above the lake, but still close to the lakeshore. I have been given some conflicting information, so I would appreciate your expertise to help me sort through the issue. I have done a few things to protect the arborvitaes. I mounded mulch around the base of the trees but paid careful attention to make sure none of the mulch is touching the trunk of the plant. I have constructed 3-foot-tall (longest stakes I could find) burlap screens in front of the most exposed trees to protect them from winds coming off the lake. Is this height sufficient? Should I also wrap the tops of the trees in burlap? I have read conflicting reports on wrapping the tops of the trees. I see you are an advocate of wrapping the trees. Is there a technique you recommend? I also bought some Wilt-Pruf. The label says not to spray until the arborvitae has "hardened off.” What does that mean? How do I know when it has happened? We have some established arborvitaes on the north side of our property that are protected from the winds. This summer, the top of one of the arborvitaes turned brown. Does this mean the tree is dying a slow death? We lopped off the top "burned part" for aesthetics. (Madison, Wis.)

A: Newly planted arborvitaes should get winter protection for at least the first year. If you can wrap them in coarse burlap to allow some sunlight penetration, that would be best. According to research, Wilt-Pruf (or any anti-transpirants) does nothing to protect the trees from wilting during the winter months, so don’t waste your time or money. The advice you refer to in your note is old stuff that did not have a solid research base to it. It was based more on empirical observations. Research out of the University of Minnesota showed that these products do not protect against water loss during winter weather. Cutting the dead top out of the arborvitae was the correct thing to do. The browning could be from insect damage, but you removed the damaged part, so it should be OK. Basically, you are on the right track. Keep in mind that these plants are native to North America and are tough as nails in their native setting. When we plant them fresh from the nursery where they have been “spoiled” to look their best, they have not developed their “war façade” to tolerate weather changes. If you get them past this first year, they should be able to stand on their own as long as you don’t overpamper them!

Q: I live in the Tampa Bay area of Florida. My hibiscus bushes are planted outside without any suffering because of our mild climate. They are thriving and growing fast, but they stopped blooming soon after I planted them. The bushes shoot out healthy leaves but never any buds. I have been told to prune them back and have done so at least three times but still no blooms. They get a lot of sunlight in the summer when the sun is high, but they are facing north. Could not enough sunlight by the problem? They are watered every couple of days. I haven't fertilized them since planting. (e-mail reference)

A: There is no reason why this environmental setting should keep your hibiscus from flowering. I suspect your soil is too high in nutrient content. At this stage, I would recommend a dose of patience. They will flower eventually. They may respond to the cooler weather coming up in the next month or two or respond to longer days of sunlight after the first of the year. Since it is a shrub, I don’t want to recommend any pruning of the roots because I think it would be too drastic. Hang in there and keep pruning it back when it gets too big.

Q: I have three spider plants at home. All the websites tell me to keep them in semibright light, water twice a week and fertilize them once in awhile. I'm starting to think I've been looking at the wrong websites because I've followed their instructions and all three spider plants are nearly dead. I started looking for parasites that could have attacked the plants, but the symptoms didn't match those of my plants. I have two cats, so I’m wondering if they took some bites out of the plants and now the plants are diseased. Are spider plants toxic to cats? (e-mail reference)

A: My cats attack our spider plants when they get a chance. After they take bites from the foliage, they vomit a few moments later. Spider plants are not considered toxic to pets. However, even plants that are nontoxic may produce a minor stomach upset in cats. While you don’t need to banish spider plants from your home, it’s still a good idea to discourage your cat from nibbling on them. Some circles claim that eating on a spider plant has a narcotic effect on cats. I don’t buy into that claim completely. The only plant I’ve seen affect cats in a narcotic manner is catnip.

Q: I have a goldfish plant that I received at my grandmother’s funeral. It is ready to be repotted but I am unsure if it needs to be in a hanging or standing pot. During the summer, I have the space for it to hang, but it’s hard to keep it out of the cold without having a standing pot during our Michigan winters. (e-mail reference)

A: As you will soon find out, this is a plant species that needs pampering. Goldfish plants need frequent misting, but the soil should be kept on the slightly dry side during the long winter months. The night temperature should be 65 or lower, which is lower than we humans like it to be. It makes no difference to the plant if it is in a hanging or standing pot. The trailing stems and flowers drape over the furniture or stand it is placed in. Since you live in Michigan, you might want to supplement the light with a plant grow light for 12 or more hours a day.

Q: I live in Chicago next to a church that had a huge silver maple tree in the backyard. It had to be about 50 feet tall and more than 100 years old. I recently was awakened by the sound of a chainsaw and a terrible shaking of my building. The pastor had decided that the tree must go because it posed a danger to the parishioners who park their cars in the parking lot. We watched in horror as they butchered and slaughtered that enormous tree. The tree was home to many neat birds during the spring and summer. Lots of squirrels used it as a safe haven and we enjoyed the shade it provided. It appeared to be a healthy tree and had a lot of leaves every year. Even in the strongest winds, I never saw branches fall. Could there have been another option? I think there could have been. Others would argue that the tree was old and its branches weak. Had the tree been better maintained and cared for, I think it could have been spared. What is your expert opinion? (e-mail reference)

A: There were other options. The action taken was very shortsighted. The thought that old equals danger or lack of substantial usefulness is wrong! What should have been done is to have the tree inspected and given annual maintenance by a certified arborist. That way, it could be determined if the tree was sound or a potential threat to the immediate community. When a sound, old tree like that is removed, it has environmental impact. As you said, it provided shade, wind buffer, a home to birds and other wildlife and aesthetics, plus its connection to history. With a little thought before any destructive action was taken, all could be enjoying this tree for many more years. This is what happens when people make judgments in areas in which they are not qualified to make them! It is right that the pastor was concerned about his flock, but he should have pulled in people who know something about trees before cutting it down. I am sorry that you lost this beautiful tree.

Q: I have a question about walnut trees. If I were to plant a black walnut tree from seed, how much do you think it would bring back in dollars from a sawmill in 30 years if it is taken well care of? Is there another tree that you think would be more profitable in 30 years? (e-mail reference)

A: I’m flattered by your question. I admit to accumulating a long lifetime of experiences and education on the subject of horticulture and trees, but this is something I cannot predict. Have you noticed how often people who are supposed to be experts on predicting the future are wrong? In my mind, documenting the past is difficult enough, so predicting the future borders on the impossible. All I can say is that black walnut trees historically have been a good investment.

Q: I read your Web page about transplanting oak trees. From what I read, it seems to be a delicate operation. I have 15 acres of oak trees here in California. There are a lot of baby trees that I would like to transplant so the forest can keep growing. Is it OK to transplant very small trees? (e-mail reference)

A: You probably can get away with moving the small trees at this time. Try to get as much of the root system as possible. It would be better if you contacted someone locally about this. You can find someone from the University of California Extension Service by going to

Q: I live on the edge of eight acres of wetland. It is owned by the local municipality and is designated as a natural park. It was deeded to the city as part of wetland mitigation by the local developer who used to own the property. Due to a construction oversight of a bordering drainage ditch, the area has flooded four times in the last six years, so we have been concerned about root rot. Sure enough, this past spring was the final blow to the trees. From my observation, I would say 70 to 85 percent of the trees have been lost. Most of the trees are box elders. I understand these are not the most desirable trees, but the area was very beautiful. The local municipality has accepted fault for the flooding and is expecting to correct the drainage ditch flaws in the spring. They are confident this will eliminate the flooding problems. Unfortunately, they do not intend to do anything about the dead trees. Other than losing a beautiful forested area, I am concerned the dead trees will create health and environmental risks. There is an entire developed neighborhood bordering the devastated area. Is there any substance to my concerns? (East Lansing, Mich.)

A: You have a valid concern. Dead trees left standing will be an attraction for mischief if nothing else. The wood should be good if the trees were killed by flooding. Perhaps you could contact a lumber company to come out and cut them down for the lumber potential they should have. I think this would be an excellent opportunity for the municipality to make points with the surrounding community by sponsoring a tree replanting. Since you live close to Michigan State University, which has a forestry and horticulture department, I think it is in a very good position to assist you in getting this oversight corrected. I urge you to contact the university.

Q: I am thinking of planting a yellow or tulip poplar in the boulevard. Is it a good choice? (Sioux Falls, S.D.)

A: Liriodendron tulipifera is a fast-growing tree that has the potential to get very large (70 feet or more in Sioux Falls). If you want something that large and the city forester approves, go for it. These are huge, majestic trees that have few problems. For me, this is too big a tree for a boulevard planting. You might check with the city to see if it has a list of recommended trees to plant on a boulevard.

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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