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Ron Smith answers questions about plants, trees and gardens.

By Ron Smith, Horticulturist

NDSU Extension Service

Q: How do I get cabbage to produce seed? Would you try if the variety were a hybrid? (e-mail reference)

A: Cabbage is a biennial, so it remains vegetative the first year. Cabbage then will go into the reproductive cycle the following year. If it is a hybrid, you are wasting your time because it will not produce.

Q: I have three European white birches planted in my front yard. After the gardeners arranged them, I noticed that they are planted over our sewer line. I wonder if I am asking for trouble leaving them there. (e-mail reference)

A: Not all trees have voracious roots that go straight down to a sewer line. Think of a ladle of pancake batter that spreads when it is poured onto a skillet. That is what a birch tree's roots also do. Most of the roots will be found in the top 12 inches of soil. Unless your sewer line is just below the soil surface, which I doubt it is, you should be OK. My advice is to leave the birch trees where they are and enjoy watching them grow and enhance your home.

Q: I have a very old black walnut tree here in Maine. It is located by a river in a valley. The tree drops about 75 gallons of nuts each fall. This year, the hulls are soft and black with little, white worms in them. I thought walnuts were used to cure worms. (e-mail reference)

A: Those are different worms, which I will not take the time to get into. These could be the larval stage of the black walnut curculio or the codling moth. The adult insects lay eggs on the developing fruit. Then the eggs hatch and the larvae bore their way into the fruit and destroy it for any marketable or edible value. Control is through a rigorous spray program once the proper pest identification has been made. Contact the Extension Service in your county to see if you can get some help in getting this very destructive insect identified and brought under control for next year. In the meantime, keep the ground around and under the tree as clean of litter as possible because many insects overwinter and become active the following spring.

Q: I can't find if there is a difference between a mini rose and miniature rose bush. Each has different instructions on the proper care. Could you please let me know? (e-mail reference)

A: As far as I know, there is no difference. If anyone knows about a difference, please let me know.

Q: A friend has an apricot tree that is about 60 years old. It has been a good fruit producer through the years. About one-third of the tree has been dead for a couple years and now another one-third seems to be dying. I believe it probably is the age of the tree, but have no idea how long of a life span an apricot tree may have. I don’t know what variety it is. We live in Idaho where our winters can be extreme. (e-mail reference)

A: If this tree is anywhere near 60 years old, it has outlived the normal life expectancy of a typical residential apricot tree. To perpetuate the tree, save some of the pits if you can and plant them this fall to see if anything comes up. In most cases, the germination is quite good.

Q: Do you have any information on trimming a Bradford pear tree? The tree never has been trimmed. I have read some horror stories about trimming pear trees. I know I need to take off some lower branches, but as far as thinning and shaping, what should be done? I asked a tree guy to do it, but I want to make sure he doesn't butcher it. (e-mail reference)

A: Lower branches can be removed to improve clearance or appearance. Generally, Bradford pears are very architectural trees and need little corrective pruning. To be sure you are not turning the tree over to a tree butcher, ask if he or she is an International Society of Arboriculture certified arborist. You can verify the information it on the society’s Web site at It has been reported to me that some will claim to be members when actually they are not. If this turns out to be the case with the arborist you are considering, report this infraction to the folks at the society. Make it clear to the arborist your reason for wanting the tree pruned and that you want the architectural form of the tree to remain intact. No arborist should leave stubs when pruning.

Q: I have a bird feeder that is stocked with suet blocks, sunflower seed, birdseed and thistle. It is high enough to discourage cats from hanging around and this summer I invented a device to keep the coons from climbing into it. Usually, there are enough birds around that something needs to be filled every week and twice a week in the winter. However, around the first week in September, all the birds disappeared. In the past week, I have seen two sparrows return, take a couple of pecks and then leave. This has not happened in previous years. Is this some cyclic thing? What are possible other causes? (e-mail reference)

A: NDSU no longer has a wildlife specialist, so I am stuck giving you unqualified advice. I would welcome any corrections from anyone who is better qualified or experienced than I am. Drawing on my own feeding observations from our backyard, I would guess that what you are observing is cyclic. My wife and I have observed the same phenomenon. My best guess is to hang in and be patient.

Q: I would like to know how to prepare geraniums for dry-root storage during the winter. (Fargo, N.D.)

A: First, allow them to become nipped by a frost. Then dig them up and carefully shake off as much of the soil from the roots as possible. Some people loosely tie them into bundles and hang them in their coolest and darkest part of the basement. Others will put them in recycled onion (mesh) bags and hang them. Cut off any diseased or weather-damaged parts of the plant back to about 4-inch stubs. Check monthly to be sure they are not getting too puckered. If the plants appear to be doing so, immerse them in tepid water to rehydrate and then rehang. Some will dust them with floured sulfur (if it is still available) to help prevent a fungal disease from getting started. When the first day of spring arrives, take them down and pot them in fresh, pasteurized potting soil. Put the plants in a sunny window and/or under some plant lights and begin a regular watering regime. Transplant outside when there is no longer a threat of a frost.

Q: I have a couple of jade plants. It froze last night, but I didn’t get a chance to move them inside. They are quite drooped this morning. Are they gone or can I save them? (e-mail reference)

A: Any exposure to freezing weather kills tropical plants. Sorry, but I'm afraid that they are goners.

Q: I have a beautiful hibiscus that I have put in a large pot in my courtyard. It bloomed beautifully all summer. Now that winter is upon us, I would like to save it. Winters here in the Pacific Northwest can be severe. (e-mail reference)

A: Survivability depends a lot on snow cover or some protection provided by the owner. You protect hibiscus much in the same fashion that roses are protected going into the winter. If you cannot bring it indoors, then allow it to go into dormancy after a freeze. Prune it back to a reasonable size and mound up some clean pasteurized or sterilized soil over the crown and shortened canes. To collect snow over the plant, erect a snow fence around it.

Q: I had to have my septic system redone, which raised havoc with my lawn. I had to have a mound system put in and the mound needs to have grass on it. Any suggestions on how to proceed with seeding grass? Any suggestions on what type of grass I should plant or what to mix in with the grass seed to really get things going in the spring? I’m thinking I will be required to put straw on the mound so it won’t freeze this winter, if that makes any difference. Would that help insulate the grass seed? (New Rockford, N.D.)

A: Get some grass seed mixture that contains about 15 percent annual or Italian rye grass and the rest Kentucky bluegrass and creeping red fescue. Instead of straw, cover the area with a germination mat, which is a fine mesh that disintegrates as the seed germinates. The annual rye should pop up in about a week and the rest next spring. If you bring in straw, you will just be adding more weed seed. The mound should be enough of an insulation to keep the system from freezing, especially if we get any kind of snow cover this winter.

Q: What information do you have about growing bittersweet in this area? Where would you suggest getting the plants? Is it best to plant in the fall? Does bittersweet grow in zone 3? I have done some looking, but I have not come up with any definite answers. I don’t know if I could just pick up the plants at a local greenhouse. Let me know what your thoughts are. (e-mail reference)

A: The American bittersweet (Celastrus scandens) is hardy in zone 3. It is a vigorously climbing vine that will continue as long as there is something to climb on! You can plant it in the fall or spring. With this plant, it makes little difference.

Q: We planted four emerald green arborvitaes this spring on the north side of our house. Slight browning occurred on every plant. We figured it was due to planting shock. However, after cutting off the brown parts, more browning occurred. One of the arborvitae looks very unhealthy. The plant has cobwebs and larger brown areas. We have not fertilized them at all, but kept them fairly well watered through summer. How should we prepare them for winter and is there any hope of the weak plant surviving? (e-mail reference)

A: It’s hard to say. It depends on the exposure and the severity of the winter. You'd better check to see if there is a warranty on these plants. If so, what extent is the warranty good for? Is it a full year replacement? Are there partial replacement costs? If you can, it would be better to get that one replaced this fall to give the root system a chance to become established before winter weather closes in.

Q: I finally got my 10-year-old Christmas cactus to bloom for the first time two years ago by taking it to the post office where I work. The heat is turned down to 55 when I leave and I kept it in a dark area. The rest of the year, it’s in a north window. Last year and now this year, it is getting buds and blooms in October, so it is finished blooming before Christmas. It only flowers that one time a year. What can I do to make it flower in November and December? I have four different kinds in one pot. They are a very pretty crimson, red, white and salmon. My customers enjoy it. (e-mail reference)

A: Good question! Usually, it is just the opposite. Our department chair had beautiful Christmas cacti in his office that bloomed when they deemed the time to be right! The only thing I can suggest is to drop the temperature lower and give them extra light (it is too late for this year) coming into the fall of the year. Apparently, the conditions at your office provide the ideal situation for flower bud initiation. Once initiated, it is like trying to stop a freight train to keep them from blooming. I'm sure your customers enjoy seeing the plants bloom. Instead of calling it a Christmas cactus, you could call it a Thanksgiving or Columbus Day cactus. Just be thankful the plants bloom. Most people would love to have your problem!

Q: I have three emerald green arborvitaes in pots on my balcony. I live in Toronto on the top floor of a building on Lake Ontario (it is very windy). I would like to bring my trees in for the winter. Will they survive? (e-mail reference)

A: Just thinking about where you live gives me a chill down my spine. It is beautiful during the summer, but unmercifully cold in winter! You are between a stone and hard spot with your arborvitaes. They need to go through the winter months to thrive, but not in containers and certainly not looking out at bitter cold Lake Ontario! Are you on good terms with the property owner? The best thing for them would be to put the pots in the ground for the winter somewhere around the building. The best spots would be the north or east side of the building. When the soil thaws next spring, pull them out and bring them back up to your balcony.

NDSU Agriculture Communication

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