Hortiscope: Plant bugs are killed with soapy water

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?...

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?

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?


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?

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.


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 .

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