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Ron Smith answers questions about plants trees and gardens.

By Ron Smith, Horticulturist

NDSU Extension Service

Q: I want to plant something to use as a privacy barrier. What type of arborvitae is best for this application? Do any arborvitae varieties attract carpenter bees or other wood-burrowing insects? (e-mail reference)

A: Brandon arborvitae is about the most columnar that I know of, so scan the market for it. If needed, get it ordered specially for your purposes. Arborvitae does not attract carpenter bees or wood-boring insects in particular. However, you have to understand that the choice as to what species of plants insects attack is pretty much up to them. Factors, such as overplanting a particular species or stressed plants, have an impact on what plants insects will target.

Q: Many of my houseplants are looking sickly. My hibiscus leaves are wilted even though the soil is wet. On some of the leaves, there is a drop of sticky liquid where the leaf meets the stem. I also received a bird’s nest fern that ended up having brown scales on the stems and leaves. I cut it down to the soil, but it is coming back. However, now I am noticing that some of my other plants have the same brown scales. Some plants have leaves that turn a lighter color, but eventually turn brown and die. I don`t know why all this is happening. I have had most of these plants for many years. Any idea what is happening and what I can do about it? (e-mail reference)

A: Glad to help. It is not unusual for houseplants to look sickly around this time of year. The long winter months and low light intensity, along with a rather passive-indifference type of care most of us give them, starts to show up on most indoor plants about now. However, I do have some suggestions for you. The hibiscus probably has some insect problems, such as spider mites, aphids or mealy bugs. Since we are close to the weather improving significantly, I would recommend that you cut the hibiscus back completely, repot in fresh potting soil and start setting the plant outdoors on nice days. Bring it in when the night temperatures are predicted to be near the freezing point. For your other plants, I have to ask, so if you already know, don't be insulted. Ferns have scalelike fruiting bodies (sexual reproductive spores) on the underside of their leaves and stems. Inexperienced plant people often mistake them for scale. That said, if this brown scale was showing up in a scattered manner and not in straight lines, then it is scale and probably has spread to your other plant material. If the infestation is light, a cotton swab soaked in soapy water wiped over the surface will take care of the problem. You didn't indicate when the plants were last repotted. Fresh potting soil will make a big difference. As I said with the hibiscus, move the plants outdoors when weather conditions permit. If you do these things, I think you'll see a big difference.

Q: I just moved into my first home. The builders planted two river birch trees in November of 2008. One tree is right next to the house, while the other tree is about 10 feet from the house. They both have tiny, green leaves all over. However, out of concern for the house, I'd like to move the trees to the backyard. I was wondering if the trees would survive if I transplanted them now. It has rained a lot lately, so the soil is very wet. Is now a good time to replant or do I have to wait until fall? (e-mail reference)

A: This would be a very vulnerable time to move the trees, so I advise against it. If you are concerned about the roots doing damage to the foundation of your house, don't worry. Many birches have been planted within 5 to 6 feet of house foundations with no detrimental effects to the house or tree. If you really want to move the trees, wait until fall after they have gone dormant. Move them with as much of the root ball as you can handle.

Q: I purchased a lovely hibiscus last summer for my mother's garden in Ottawa, Canada. I planted it in the garden, but brought it inside last fall using soil from the garden. My husband and I have waged a largely unsuccessful battle against what we thought were aphids using SAFER's Insecticidal soap. It is now April, but I’m hoping to put a healthy plant back in my mother's garden on May 24. We have not fed the plant all winter. We gave it city tap water and did a regular soaping against the aphids. Given what I have been reading in your column, I'm not sure if we should be feeding it, cutting it back or continuing with the SAFER's and watering. Your help would be much appreciated because our growing season is so short. We try to get as much as we can out of the garden! (e-mail reference)

A: From one short growing season gardener to another, I recommend cutting the hibiscus back to about 4- to 6-inch stubs and setting the plant outdoors during nice days. If the temperature indicates freezing at night, then bring it in or cover it (assuming the forecast isn't drastically low). You should see new growth beginning with this change of location. After it is evident, lightly fertilize until you get it planted in May. However, don't risk using native soil when moving the plant this fall. You are lucky that the plant survived this situation. You are better off getting some commercially available potting soil, such as Miracle-Gro, and using it for houseplant purposes, even on a temporary basis.

Q: I got a lovely variegated ficus tree last fall. I put it in front of a south window with the blinds nearly closed all the time. Unfortunately, there is a cold air return there. I keep my house at about 64 degrees during the day and 59 degrees at night. I have been misting the tree a couple of times a day on most days, but have not overwatered. It has lost more than half its leaves, but seems to have stopped in the last month or so. When will the leaves start returning? Do they regrow where the little stems are? Should I start giving it plant food? What else do you recommend? (e-mail reference)

A: You are putting your poor ficus, as well as yourself, through a low-temperature boot camp! If the tree is recovering at all, it is because more light is getting to the plant somehow with the gradual arrival of spring. You cannot expect the plant to survive under such conditions. This tropical plant has not experienced low temperatures and low-light conditions. If possible, when the weather stabilizes where you live (no threats of frost), I would encourage you to move the plant outdoors to the east or north side of your house so it can get some light, but not sunburn from excessive light. Fertilize when there is evidence of active growth.

Q: Two years ago, I planted a potentilla in a sunny spot. It did great for two years. This spring, I noticed, to my astonishment, that something had chewed every branch down to the ground! There is a thin branch sticking straight up out of the center of the plant. It has a few pitiful new leaves growing on it. We live in a well-established suburb with a tall fence around the entire backyard, so this could not have been done by deer. What on earth could have done this? Can I anticipate new growth? How can I prevent it from happening again? (e-mail reference)

A: Look around your yard for evidence of cottontail activity. Rabbits will do the same thing to a shrub that deer will. Cut it down to the crown. If the plant went into the winter in a healthy, robust state, chances are very good it will recover this growing season, so be patient. Before snowy weather arrives next fall, put up an exclusion fence (chicken or rabbit wire) around it or put your faith in one of the many rabbit repellents on the market. Trust me that the exclusion fence will work better.

Q: Is it possible to plant 100 bulbs this April and have them come up this year? We are in southern Ontario. (e-mail reference)

A: I doubt it, unless you are talking about summer bulbs, which would make April too early for such planting. I suspect you mean tulip, daffodil or crocus bulbs. They should have been planted last September or October (the latest) to get good blooms and sustainability for subsequent years. If the soil is not frozen, you might as well stick them in the ground to see what happens. If you haven't purchased them yet, don't do it. The quality may not be there and you are helping someone else get rid of something they know won't work or will perform poorly.

Q: We have a very pretty willow tree in our front yard. It was planted right next to a pond that we have now filled in and made into a rock garden. I know it is a willow, but I don't know what kind. It has small, golden green leaves that hang down to the ground like a weeping willow. Until last summer, it seemed fine. Now we have noticed that some of the branches are black and dying. We cut and pruned them away. What is happening? Some of the lower branches (thicker ones close to the trunk) seemed to be twisting around each other. (e-mail reference)

A: The tree sounds like a typical weeping willow, which is one of the more common trees seen throughout American landscapes in the north. Unfortunately for this beautiful tree, there are hordes of pathogens and insects that adopt it to live and multiply in. Some of them are bacterial twig blight, crown gall, black canker, rust, tar spot, aphids, willow galls and willow scurfy scale. The species is a living lab for plant pathologists, entomologists and horticulturists to study. All of this doesn't help you solve the problem you are observing, so I suggest that you contact a local International Society of Arboretum certified arborist to inspect the tree to get the disease or diseases identified. The arborist can give you proper recommendations to control any further spread of the problem.

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) 231-8161,
Editor:Rich Mattern, (701) 231-6136,
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