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

By Ron Smith, Horticulturist

NDSU Extension Service

Q: I was reading your Web site about the care of Christmas cactus plants, but haven't found exactly what I need to know. I was trying to find out why my plant, which I have had for several years, is looking droopy and the leaves are turning purple at the tip instead of the normal green. The weird thing is that the top of the soil in the pot is covered with algae. (e-mail reference)

A: I can't tell you why the plant is changing color and the leaves are droopy. I can tell you that the plant probably will respond well to repotting in fresh soil. This often brings about favorable changes. Your soil may be too acidic as indicated by the algae growth, and could be causing the discoloration. As the soil becomes more acidic, the balance of what is available to the plant shifts from being deficient in some cases to being toxic in others.

Q: Rabbits are digging their way under my house and nesting. They have holes all around my home. We filled in the holes, but the rabbits came back a few days later and dug new holes. I have tried rubber snakes, moth balls, dried blood and pepper to keep the rabbits away, but nothing has worked. (e-mail reference)

A: Have-A-Heart live traps are what I would suggest using next. These traps usually can be borrowed from the Department of Natural Resources in your state or purchased from a farm supply store. Once you trap a rabbit, you have to decide what to do with the animal. There are recipes for rabbit or you can release the animal out in the country.

Q: Someone told me that I never should eat apples that have sat on the ground. Is this valid? I often pick my golden delicious apples that fell to the ground. Thanks so much for your time. (e-mail reference)

A: Did he or she tell you why? Some orchards will have wind-drop apple sales, which we have participated in several times without problems. Of course, you don't pick up any that are wormy or rotting. In a nutshell, this is another invalid rumor, so enjoy!

Q: I have discovered the beauty of ornamental grasses. However, the only variety I have is Karl Forrester. I have seen one that is taller and has a white plume on it, but the local gardener could not remember the name of it. The gardener was surprised that it was winter hardy for North Dakota. Do you have any suggestions for any ornamental grasses? Can they be planted now or should I wait until spring? My son is an NDSU student. Last summer, he took a walk through the NDSU test garden. He wrote down the names of several of his favorite flowers. Is there a way he can get seed samples or starter plants of any of the flowers he liked? (Hazen, N.D.)

A: I'm with you 100 percent on the beauty of ornamental grasses. There is no better start than the Karl Forrester! The one you are making reference to is called miscanthus sinensis/silberfedher. We also have it growing at the Williston Research Extension Center. Another easily grown ornamental is native switchgrass/panicum virgatum. For a groundcover type, the feeseys form ribbongrass is hard to beat. I am sorry, but we are not allowed to distribute seeds or plants. Our horticulture club has an annual spring sale that is very popular. The sale usually is around the middle of April.

Q: My sister bought an alstromeria (bulb) that bloomed all summer. She took it inside for the winter and now it has a dozen shoots coming up. What do you know about it? (e-mail reference)

A: Not enough to be considered an expert! The plant probably will not get enough light from normal interior lighting conditions during the winter months. The first thing I would suggest is to get a plant light shining directly on the container for 12 continuous hours a day. Next, be sure it is in a warm location, but not hot. Keep it away from a cold and drafty location. Through the winter months, keep the plant moist, but not soggy. Set it outside again after the spring frosts are no longer a threat. As for fertilization, do so when active growth is taking place. Use a high phosphorus and potassium material. Perhaps a reader will be able to supply more details based on experience.

Q: I have a huge, old silver maple that is very close to my house. It’s starting to lose branches and one damaged my neighbor’s fence. I had three companies look at it. Two companies said the tree was OK and would charge me $1,200 to trim and cable it. One said it looks bad and should be taken down at a cost of $3,000. My main concern is safety and doing damage to my neighbor’s property. What should I base my decision on? Should I take it down to be on the safe side? (e-mail reference)

A: Without a doubt, take it down. Cabling and bracing are done when champion or specimen trees need to be saved and are not a safety threat. Make sure the company taking it down is insured and bonded. While it is being removed, you and your family should stay out of the area. Even people who know what they are doing can be fooled by a tree falling in an unexpected direction.

Q: We have several cottonwood trees on our property here in southeastern Michigan. We have a double cottonwood tree with trunks that touch at ground level. Can we safely remove one trunk? If so, where should the cut line be? We are not planning to remove the stump. For all the other cottonwoods, can we safely trim or remove branches from the ground up to about 25 to 30 feet? (e-mail reference)

A: This would require an inspection to give you accurate guidelines. Generally, cut anywhere above where the two trunks are joined. Any major tree work of this nature should be done by an International Society of Arboriculture certified arborist and not just someone who is handy with a chainsaw. As for your other question about trimming, yes, you can.

Q: We have a Christmas cactus that we put outdoors the last two summers. It is amazing how the plant flourishes. This year we seem to have a bug problem when we brought the plant inside for the winter. We have been inundated with fruit flies. What can we do? (e-mail reference)

A: In general, fruit flies and gnats can be enough to drive someone crazy. The life cycles of these insects are measured in days, so their multiplication is nothing short of phenomenal. Get yellow sticky cards from a local florist or nursery and place them around the plant. They usually come with twist ties that you can attach to small pieces of bamboo. Once stuck on the cards or tape, the bugs are doomed. Once you start using your central heating system, the air becomes drier and kills the bugs from dehydration. You might be lucky enough to be rid of the bugs in a few days. If not, then you need to find one of the more potent treatments that give off a vapor that is toxic to insects. The problem with these treatments is that they are toxic to us, as well. The usual procedure is to place the plant in a plastic bag with the strips, seal it and place it in an unused room that you can vent after use. Usually a 24-hour exposure to these strips takes care of all insect life. You then throw the bag and strips away. A less toxic approach is to repot the plant in pasteurized potting soil. Clean the pot or replace it. That also would take care of the bugs. I suggest trying the combination of sticky cards and repotting before resorting to the more toxic approach.

Q: I enjoy your column very much. However, I've never seen anything on jasmine plants. A few years ago, I purchased a blooming jasmine and loved it all summer. I've managed to keep it alive and growing, but it no longer blooms. Should it be pruned? Does it need a resting period? I do put it outside for the warm months. When the plant was new, it looked like a small bush. Now it looks like a wild vine. Any help will be much appreciated. (Mobridge, S.D.)

A: You have picked a challenging plant to grow in South Dakota, but it’s worth the effort once you smell the fragrance of the flower! In growing them in landscapes, they grow best when the plants get at least four or more hours of direct sunlight every day. Jasmine will grow into a bush or vine, depending on the species you have. Both types should be pruned to keep them in form and encourage flowering. Regular applications of a low-nitrogen, high-phosphorus and potassium fertilizer, such as a 5-10-10, should be made to encourage flowering. Try to locate the plant near a south-facing window if possible during the winter months and in as sunny a spot as possible while the plant is outdoors during the summer.

Q: I have a river birch that needs to be pruned. Can I have it trimmed now or should I wait and have it done in February or March? I live in Michigan. I need to have some large branches removed because they are hanging over my house. (e-mail reference)

A: I would make sure to get someone who knows what he or she is doing because birch trees do not take well to inappropriate pruning. Try to find an International Society of Arboriculture certified arborist who has good credentials and experience pruning birch trees on residential properties. The tree can be pruned anytime that it can be scheduled. I've had my cutleaf weeping birch pruned in late winter as well as summer. It is doing OK mostly because the chap who did the cutting knew what he was doing.

Q: I am looking at potential seed treatment opportunities for residential turfgrass. I was hoping you might be able to direct me to where I could get a sense of the potential needs or uses for pelleting or priming turfgrass. (e-mail reference)

A: Priming is a very accepted practice for sports turf managers who need to get grass up quickly. It often is done in large quantities and mixed with an organic fertilizer, such as Milorganite, to be spread over bare areas. Pelletized seed is very effective as well, but adds considerably to the cost of the seed. Nick Christians at Iowa State University is considered a national turfgrass guru. I would suggest contacting him or the department for more detailed information.

Q: I have what I call two jade “stalks.” I’ve had them for a number of years, but they never grow. The top leaves are getting a little bigger, but that is all. What gives? (e-mail reference)

A: The plant doesn't like something in the environment or something that you are doing or not doing. Jade, like many houseplants, needs strong, indirect light. However, direct sunlight is OK during the winter months. To correct the problem with the foliage at the top, I would suggest that you cut the stalk back. Take what you have pruned and cut into 4-inch pieces to root. Lay the cut pieces in a bed of damp, unmilled sphagnum moss. Barely cover the pieces. After six weeks or so, there should be some leaves coming from the top part of the cuttings and roots developing at the base. After the roots get to ample volume, pot the cuttings in a pasteurized media. As for the stalk that has no roots, that is because of deficient leafing volume. You probably cannot change what has taken place, so I would suggest dumping that character and replacing it with one of the new plants.

Q: Some of the leaves on my ficus trees are curling. It appears there is some sort of bug inside the leaves. The other leaves are a healthy looking green. New leaves also are being affected. One ficus is in the ground and the other is in a pot on the front porch. Several months ago, I noticed this leaf curling on the tree sitting on the porch. I treated it with Malathion, which seemed to make the problem go away. Now the tree in the ground has the same leaf curl problem. Both trees get more than adequate water. (e-mail reference)

A: This is very likely some species of aphid that has decided to raise a family in your ficus trees. While Malathion is effective, resistance can build up to it and cause foliar burn. I would suggest a systemic, such as Bayer's Advanced Tree and Shrub Insect Control (Merit), which provides up to 12 months of protection. We've done some field tests with this material and found it to be effective, at least in our region of the country, for one growing season.

Q: I am getting ready to prune my grape vines. A friend is wondering if he can get starts off of what I prune. Can this be done successfully? Please list the proper procedure if it can.(e-mail reference)

A: You can. The best way to do this is to cut the pieces into 12- to 18-inch lengths and root them now, depending on your facilities and where you live, or wait until spring. Stick them into well-drained soil in a pot to get them off to a good start. They easily root with little fussing. Once rooted, you can pop them out of the containers and plant them where you want.

Q: I purchased a house in 1984 that came with a Haralson apple tree that was producing when I moved in and has been ever since. Some years more than others, but I always have apples. I don't know the age of the tree. A large limb broke this year from the weight of the apples, but I propped it up until the harvest. I need to take down the limb. How far can I prune this tree? I would need to prune all around to balance it. I have pruned in the past, but never as much as I need to this year. Should I take it in steps? Prune some this year and some next year? I hate to lose the tree because it always looks and smells beautiful in the spring and does give us hundreds of apples most years. I do pinch the buds, so only one remains from the flower cluster, but maybe I need to pinch more. What is the life span of a tree like this? Thank you for your answer. (e-mail reference)

A: The life span I have seen for apple trees is about 25 to 40 years. Staged pruning would be better for the tree. Cut the branch back as far as necessary, but never cut into the main trunk, especially on a tree as old as yours. Do the pruning in the early spring before new leaves emerge. This will encourage faster wound healing. You are doing the right thing by removing a major number of flower buds. It gives you bigger, but fewer, apples. In your case, that doesn't sound like a sacrifice!

NDSU Agriculture Communication

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