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

By Ron Smith, Horticulturist

NDSU Extension Service

Q: I read your column in our local newspaper every week and find it to be very helpful. We had a bad problem with apple maggots in two of our apple trees the last two years. Last spring, we sprayed the trees and the ground with a systemic spray before the fruit set. On one tree this fall, every apple was destroyed by maggots, so I picked them all and got rid of them. The other tree had a few good apples. I really tried to keep the fallen apples picked up after they fell but could not always get it done every day. Do you have any suggestions? I also am wondering if it is healthy to eat the apples that have the bad areas cut out. Thank you for your help. (Jamestown, N.D.)

A: Cutting away the bad sections of an apple is OK. A number of approaches work to control apple maggots. Picking up all the fallen fruit and removing any that might still be on the tree is one of them. Using pheromone traps is another method of control. The traps hang in the tree and attract the fly, which is the adult stage of the maggot. Once in the trap, the fly cannot reproduce to later lay eggs in the apples. Another tactic is to get an apple maggot kit (a fake apple that is covered with a sticky substance). The female gets stuck on the fake apple and dies. Finally, bagging the apples will keep the fly from laying her eggs under the skin. The next step is the timing of your spray program and what you use. For this, I will refer you to a publication on the subject put out by the University of Minnesota. It is available at

Q: My sister gave me three ferns to take care of this winter. They have more of a yellow frond instead of being bright green. They also have extremely long, hairy pieces coming out of them. I have cut them back but am wondering how to care for them this winter. I have no idea what type of ferns they are. How often should the plants be watered and how much sunlight do they need? (e-mail reference)

A: In general, ferns thrive in a moist environmental atmosphere and normal household lighting conditions. Their root mass should be misted at least once a day with distilled water and the fronds a couple of times per day, especially when the central heating system is drying out the air. In other words, the lower the outside temperature, the more the heating system will run and dry out the air. This leads to greater vigilance on your part to keep the plant fronds from drying out. However, some fronds are bound to dry out. When they do, cut them off at the base. Don't expect them to come through the long winter months looking as good as they do right now. Even under the best of care, ferns usually struggle and look pretty ragged after a long winter indoors.

Q: I came across your Hortiscope page while trying to get more information on a mystery plant I suspect is a hibiscus. I live in southern Ohio and have a neighbor who is a serial plant killer. The plant I picked up has dull, green, unserrated, somewhat heart-shaped leaves and woody stems. It had two dying red flowers about the size of my palm. Its leaves were drooping but of good color. The plant looks to me like it had been underwatered, which is like the last two plants the neighbor left on the curb. I gave it some water and took it to my porch. We've just had our first hard frost about two days ago, so I decided to cover it in plastic in case it can't handle frost. It doesn’t appear to have any insect problems. However, I gave it a quick shot of insecticidal soap just in case. If it is a hibiscus and it doesn't perk up, should I cut it back hard to see what happens? Otherwise, if it is a hibiscus and it does perk up, what would be the best way to bring it inside? (e-mail reference)

A: Either way, it probably would be a good idea to cut it back hard to see what happens. I’m guessing that it may be a tropical hibiscus, so it would be very intolerant to any significant cold. I would advise getting it indoors at your earliest opportunity. Put the plant in a brightly illuminated location (south- or west-facing window). Keep the plant adequately watered through the winter months and give it diluted shots of fertilizer if any new growth becomes evident.

Q: Do you trim back strawberry plants in the fall the same as perennial flowers or just cover them? Thanks for any hints! (e-mail reference)

A: You can trim them in the fall or spring, but I've done it in the spring to help clean everything up for the new surge of growth. Make it one of the last things you do before having the mower serviced and the blade sharpened. Collect the clippings in the mower bag. Right after that, I suggest a shot of water-soluble fertilizer to give the plants a boost.

Q: Please settle a friendly discussion concerning the correct height to mow the lawn before winter sets in. My husband believes the grass should be kept longer to retain snow and moisture. I believe that a short cutting is healthier because it helps prevent mold growing under the snow. (Fargo, N.D.)

A: I settled this discussion for my daughter and her husband this past weekend. In your case, you are correct! The longer grass will mat down and be a source of snow mold development during the winter months. Of course, other conditions must be in place for it to develop, but leaving the grass longer going into winter is a good beginning point for this pathogen. Lower the mower setting at least a full inch but not low enough that scalping takes place when mowing. If this turns out to be a chronic problem with your lawn, plan to have it core aerated sometime next summer.

Q: I am looking at putting in some grapevines next year. Can you recommend a grape that is good for eating and making jam and jelly? Could you tell me approximately what each vine yields and how many plants I should start with? (Fargo, N.D.)

A: I am going to give you several references to review so that you can arrive at your own decision. For information, go to or The North Dakota Grape Growers Association has a website at that you might be interested in. Most members grow their grapes for wine, but some do so for jelly. Two other sources are at and All of this should give you good “dream material” to think about through our long winter months.

Q: I bought a small shoot of a raspberry plant and potted it. I'm a new gardener, so I didn't realize I needed to fertilize the soil before planting. Recently, I saw that the leaves are crunchy and dry even though I've been watering the plant. Do you know what's causing this problem? How do I prune the plant, and is it OK to let it stay in a pot? I don't really have a proper garden. (e-mail reference)

A: If you potted the raspberry into a good-draining container and used standard potting soil, the plant should be fine without any fertilization. If you’ve had it outside anywhere north of the Mason-Dixon Line, the leaves should be brown and crisp because of the colder fall weather and fewer hours of sunlight. When new growth begins next spring, it would benefit the plant to get a shot of fertilizer. Depending on where you live, raspberry plants can tolerate being kept in a pot for about three years before they will have to dug up, split and repotted.

Q: I just started some baby spider plants (four green and four variegated and striped). I hope they survive. The plants had very tiny roots, but I went ahead and put them into the soil. Is there a good chance they will survive or should I have left them connected to the parent for a while longer? Also, is there a guideline for how much light they should receive each day? I'm in Connecticut, so the amount of daylight is decreasing. Is this going to make them grow slower or keep them from developing properly? (e-mail reference)

A: The baby spiderettes should become established during the winter months. Since they are so small, I would suggest giving the plants supplemental lighting to provide more energy for root development. Give the plants 14 hours of light per day.

Q: Could you by any chance give me information on how to shell a black walnut? My neighbor has a tree that is loaded with nuts. (Grand Forks, N.D.)

A: Let me count the ways on how to crack a black walnut to collect the nutmeat inside. A sledgehammer and slab of concrete requires just the right touch or else you’ll smash the nut to smithereens. You could use a Ford F-150 pickup truck with steel-belted tires to full legal inflation to drive over the nuts. Don’t use an F-250 because we found the weight of the truck to be a little over the top, so the shells and nutmeat were crushed beyond separation. You could round up some neighborhood crows. Through their own independent and valid research, they know just the right height to fly to get the shell to crack just right so they can pick out the nutmeat with ease. A big disadvantage is that crows get very territorial and don’t like sharing their bounty with humans. The solution is to have a dog at your side to chase the crows away as you hurry to pick up the cracked nuts. You can use a mounted vise if you would like. Place a nut in the vise with its seams parallel to the vise jaws. Tighten the vise until the shell splits open. If you need extra leverage, you can slip a length of pipe over the vise handle. Using a rubber mallet to tap the handle until it's tight also may be helpful. Once the nut has cracked, you can dislodge the meat by shaking or prying it loose. With this method, the nutmeat will come out in four neat quarters and be nothing like the black walnut dust offered in supermarkets. Store the nuts in the refrigerator or freezer until you need them. This is assuming, of course, that you have carefully removed the nuts from the green husk, floated them in a bucket of water and discarded the floaters. Drain the water from the remaining nuts and dry them in an herb drier or spread them out somewhere on a screen or newspaper to dry. Once they are determined to be completely dry (the herb dryer works best), then graduate to the vise technique. You should know that the husk meat will blacken anything it touches and takes about a week to wear off with diligent scrubbing, so protective gloves are recommended. Be aware that when cracking the nuts in a vise that shell fragments can fly off everywhere, so wear protective glasses. Finally, I’m sure if you shop around and are willing to spend a few dollars you can find a black walnut cracker that will do this job mechanically for you. Usually when all of this is understood and attempted, people see the reason why shelled black walnuts cost more than $7 a pound, which some are willing to pay for this convenience.

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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