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Ron answers reader's questions about the world of plants and gardening.

By Ron Smith, Horticulturist

NDSU Extension Service

Q: I've noticed that my maple tree has little, round, green, raised dots on the leaves. Some leaves have as many as 25 to 50. It's almost like reading Braille. I would like to know what I can do to get rid of these pests other than cutting off the infected leaves. (e-mail reference)

A: These are galls caused by mites early in the season. This is not a problem for the tree, but does change the cosmetic character of the tree. The galls are temporary and probably will be gone by next year's growth. There is nothing you can do about it, so relax and enjoy what remains of the summer!

Q: I planted a ruby red horse chestnut tree. The first two years the tree did very well. This spring the buds formed and it looked as though the tree would do well once again. However, only a few buds opened to form leaves. I'm worried the tree is in jeopardy of being lost. Is it too late to save the tree? Is there anything that I can do to help force the rest of the buds to open? Is there anything that I should do prior to winter? (e-mail reference)

A: It doesn't sound good for the tree at this stage. I would suggest replacing it or going with a different type of tree. Sometimes special cultivars, such as ruby red, don't thrive as well as the species, which leaves a lot of disappointed consumers. When they do well, everyone loves them! However, they often are planted in less than an ideal environment, which brings the results you describe.

Q: I planted two maples on either side of my driveway hoping to create an archway. That was three years ago and they've been doing fine. This year, the leaves on both trees came in on the bottom half, but the top half seems dead. I have no idea if I should trim them and hope for the best or if there is a fertilizer I can give them. I hope you can help. (e-mail reference)

A: Before you go any further, try to determine what killed the top half of the trees. It may have been bark beetles or borers. If it was a response to the environment, then go ahead and cut the dead parts out and see if you can get a new leader started.

Q: I have a crimson king that has curled and dried leaves this year. However, it has many buds on its branches. There are many broken branches from children bending the tree down to the ground. Is there any way to save this tree? (e-mail reference)

A: I don't think the tree will survive. I would suggest replacing it with another tree of a different species because crimson king trees are difficult to get established. Get the neighborhood kids who relish bending trees to assist in planting and protecting the tree from other mischievous kids. That will help any tree survive!

Q: I purchased a hibiscus braided tree in early July. I've kept it indoors under a skylight. It is loosing its flowers and a lot of leaves are turning yellow. I haven't repotted the tree and I water it a lot. I also put one stick of Miracle-Gro Plant Food for Indoor Plants in the soil. Should I be concerned? (e-mail reference)

A: Remove the fertilizer stick and keep the soil moderately moist, but not soggy. The plant is going through a transition to the new and apparently harsh environment, but it should recover. Be patient and try not to push it too hard with fertilizer or overwatering.

Q: My husband and I pulled out a fire blight-infested cotoneaster hedge that was along two sides of our patio. We have several apple trees in our yard and probably shouldn’t have been using cotoneaster as a hedge anyway. The patio is on the west side of our house and gets plenty of sunlight, but is shaded by a silver maple tree late in the day. Is there something you could suggest as a replacement? I loved the wild look of the cotoneaster. We trimmed it every two years, so we don’t need anything formal looking. I read your Web page, but there were too many suggestions for me to make up my mind. Our yard is very protected by shelterbelts. Any direction you could give me would be much appreciated. (Fargo, N.D.)

A: Try some viburnums. There are several, such as the nannyberry viburnum, that will give you the natural look you want. It has everything going for it, such as an informal appearance, beautiful flowers, edible fruit and good fall color. What more could you want?

Q: I am growing a tomatillo plant. The plant is very healthy, but the flowers keep falling off. I water the plant in the mornings. I don't know what I am doing wrong. (e-mail reference)

A: This could be due to a variation in watering cycles, hot/cold weather shifts, too much nitrogen fertilizer, failure to fertilize the flowers causing abortion or some other stress factor. Try not to overwater because these usually are very productive plants once they get established.

Q: My silver maples always have a huge amount of helicopters in the spring. This year there were none. Should I be concerned? (e-mail reference)

A: If the tree is healthy, find something else to worry about. Sometimes trees get into alternate bearing if the preceding year there was a heavy fruit (or seed) set. Enjoy a summer without a lot of volunteers coming up everywhere!

Q: I am told that hollyhocks are easy to grow. Do gophers like hollyhocks? I have a lot of them. When is the best time to plant? I live in the mountains of southern California, so temperatures get down to the 10- to 20-degree range during the winter. During the summer we get a lot of sun, but very little rain (none this year). How often do hollyhocks need to be watered? (e-mail reference)

A: Gophers, bunnies and field mice seem to love hollyhocks. Plant them in the early spring or fall (it makes little difference). The winter temperatures you describe are not a problem. If you don't provide any water during the summer, you might as well forget about growing them. However, they don't need much water.

Q: I read your column where you talked against rock landscaping for shrubs around the house. What is the reason for not doing this? We had a nursery put in shrubs along with rock several years ago. I also read that the rocks provide too much heat. Is this the reason my shrubs seem to be doing well, except for some gold mound spirea on the east side? If the rocks are holding too much heat for them, would it be advisable to remove the rocks in a larger area around each shrub? They are pale in color, not growing well and have lots of dead branches. I water when they need it and gave them a little Miracle-Gro this spring. (LaMoure County, N.D.)

A: Rock does create heat islands around the plants. The rock also tends to migrate out of the beds and into the turf. It does nothing to condition the soil and tends to compact the soil beneath it, which forces the air out of the root zones. If the plants do grow under a rock covering, the plant stems or trunk tend to be compressed or even girdled if the homeowner does not move the rock away from the enlarging plants. Also, the rocks just are not natural in appearance. As for weed control, dirt and weed seed still blow in. Unless the owner is fastidious in hand removing the emerging weeds, most people will spray with Roundup and leave the dead weeds behind, which is unsightly. Enough reasons? Remove the rock from your spirea, which may improve the condition of the plant.

Q: We have several arborvitaes lining our backyard. We noticed that one of them has some type of worm that’s devouring the tree on one side. The worm is black or gray in color and has tiny stripes on it. We’ve never had a problem with them before, so we’re unsure what type of worm this is and what to do with it. We applied Sevin dust with the hope that it will help. Is there another product that we can or should use? Is there something we could have done to prevent this problem? (e-mail reference)

A: You couldn't have done anything to prevent the problem. The Sevin insecticide should slow them down somewhat. You could use an Ortho product for control because the products have systemic characteristics. If the plant munchers come back, they would not devour too much before succumbing to insecticide ingestion.

Q: I'm trying to grow a barrier behind my house for privacy and wind protection. I planted blue spruce trees about 10 years ago, but a disease killed them. The lawn slopes to a wet area that at one time was an artesian well. I suspect there is a high salt content in this ground because of the old well. The ground is cold and has thick, clay subsoil. Will arborvitaes survive in this environment? Is nigra or tahny a better choice? (Alice, N.D.)

A: We are finding high salt levels in a lot of North Dakota ground water. Soil that is cold will stay wet longer, which gives any evergreen little chance of surviving. Quaking aspen and willows are the best choices I can give you without knowing anything else about your situation. If you order arborvitaes, I'm afraid you will regret doing so, unless you can do something to pull the water and salts away from the roots.

Q: I planted three hydrangeas last summer. Before winter came, I noticed little buds growing, so I didn't trim it. In the spring, the plant seemed to start growing again, but then we had a late snow. It looks dead at this point. Should I let it go another winter and see if it comes back next spring? I don't know what type of hydrangea it is. I think the blooms were a purplish blue. I live in zone 5. (e-mail reference)

A: If it has not leafed out by this time, it is dead. Replace it with something that is hardy to your area. You very likely received florist hydrangeas that were not hardy for your zone.

NDSU Agriculture Communication

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