March 15, 2001

Hortiscope

Ronald C. Smith, Horticulturist
NDSU Extension Service

Q: Could you tell me what to use to spray plum trees while in bloom and bearing fruit, etc. to prevent the little bug sting that is on the fruit once it bears? (E-mail reference, Georgia)

A: Sevin is an acceptable insecticide to use at petal-fall. This insecticide is extremely toxic to bees, so spray only when the bees are inactive, early morning or late evening. You will want to spray again when the foliage is fully expanded, and again about 20 to 30 days later. Good sanitation -- picking up the dropped fruit -- will also help control this pest. The insect you are trying to control is known as the plum curculio and likely has two generations in your part of the country.

Q: I just noticed that the rabbits stripped off about a 4-inch piece of bark around the trunk of my best 5-year-old ash tree. This is the first time they have bothered it. We had plastic wrapping around it, but I noticed that the way the snow has drifted this year the snow is now higher than the wrap. Would it be best to dig out around the tree so that they can't get any higher? Is there anything we should do to repair the tree later? Will the rabbits continue to eat further into the tree, or do they just want the bark? I have no experience with tree problems and don't know what to do. (E-mail reference)

A: As long as the tree was not girdled it will most likely be all right. The rabbits are desperate now, with the thick snow cover, in their search for food. Digging out around the tree would help; wrapping the tree with aluminum foil at the current snow height would also help; spraying a pepper spray on the branches and trunk would also help; using a material such as Ropel, which has a bitter taste, would help as well. Notice that I am using the words "would help," not stop or cure. They are persistent animals at foraging for food, and quite frankly, if you would feed them sunflower or corn, they would much rather eat that than the bark off your trees. I know this is like "feeding the enemy," but if your objective is to keep your plant material from being damaged, rabbits are smart enough to go the path of least resistance, eat what you put out for them, and pretty much leave your plant material alone. By the way, live trapping also helps. Just transport them a minimum of three miles away.

Q: My schefflera trees are about 18 years old. I keep them indoors during the winter and outside during warm months. This winter a "sticky" liquid is dropping from the trees onto the floor. I cannot see scale or other pests. Can you offer suggestions on how to treat the leaves to keep them from dropping the sticky liquid? They get good light, afternoon sun and I do not over water them. One tree is 10 feet tall and the other is 12 feet. I would not like to dispose of them, but if they have an untreatable disease, then I will have get rid of them. (E-mail reference, Augusta, Ga.)

A: I suspect that you may have spider mites doing some feeding on the leaf undersides. They are about the size of the dot at the end of a sentence and blend in quite nicely with the green foliage of the plant. Look for little webbing on the leaf edges. Try taking a damp sponge and wiping the upper and lower surfaces of the leaves off. This will remove any mites present. Do this every two weeks, especially during the winter months when the interior air is so dry. It wouldn't hurt to mist the foliage with distilled water either on a regular basis, like three or four times a week. If this doesn't stop the sticky dripping, then I'd suggest getting rid of it. In the meantime, place a tarp or old tablecloth under the leaves to protect the flooring.

Q: Last year I sent you a question regarding my petunias with yellow leaves. I took your advice to add peat to the area. I also added cow manure, and with the combination of the peat and manure, I had beautiful petunias last year. Now I have another question. I have heard sunflower hulls do not make a good mulch because there is a chemical in them that retards growth. Do you have any information regarding this issue? I feed sunflower seeds in my bird feeders so have lots of hulls to dispose of. I would like to use the hulls in my garden but have been reluctant to do so because of what I have heard about them. (E-mail reference, Beach, N.D.)

A: Glad my past advice worked out for you. Sunflower hulls, to my knowledge, should not hurt the growth of your petunias. The hull is about as inert as you can get, so I don't know of anything toxic that could leach out and cause a problem. My advice: go ahead and use them where you want.

Q: We are planning to plant plum trees this spring and are wondering if the Pipestone and Toka are the most hardy varieties for zone 3 on the Minnesota - Canadian border. Or are there other varieties which are both hardy and produce well? (E-mail reference, Baudette, M.inn.)

A: Those are a couple of good ones to use. They produced well for me in my backyard.

Q: Are the dandelions that we have edible? What parts can you eat? What is the nutrient value of this plant? (E-mail reference, Carson, N.D.)

A: Here are the facts on dandelions: the young spring leaves are eaten for their vitamin A content and for a diuretic effect. They are mixed in salads, to dilute their somewhat bitter taste (which is prized in Pennsylvania Dutch cooking!). The interesting thing about the diuretic effect of dandelion leaves is that it behaves differently with the body than typical pharmaceutical diuretics. It restores the potassium lost through increased urination. The root can be roasted as a coffee substitute; the flower collected and made into a wine. Will we ever win in the battle against dandelions? I certainly hope not, it may become a major part of our food chain in the future! (Information was gleaned from "The Herbal Drugstore" by Linda B. White, M.D. and Steven Foster. Published 2000.)

Q: Do flowering crab trees have a life cycle or age limit? We are fighting leaf spot and/or apple scab on a very large tree, about 20 feet tall. I'm going to buy better fungicide delivery equipment but only if there is a chance to save it. The tree is about 23 years old. (E-mail reference)

A: There is a probability that you can save it, but if it is prone to apple scab or other diseases, it will be an annual fight, and one that usually get worse as time passes. You are better off having the tree removed and replacing it with one that has resistance bred into it.

Q: I received a beautiful plant for my birthday called a Kalanchoe (Kalanchoe blossfeldiana) I keep it in my office. It seems to like the fluorescent lights. The card says to maintain soil on dry side and to fertilize starting two to three weeks after purchase.

What type of fertilizer should I use? We just noticed that there are two plants in the pot. Should I divide them? It is a fairly large plant, the blossoms (dark to pale pink) seem to still be okay.

People comment on the plant when they come in and I don't know what to tell them. I can't even pronounce the name! (Mandan, N.D.)

A: What a nice gift to get! They are beautiful plants, and are easily cared for. There are any number of houseplant fertilizers you can use. Shop locally and see if they have Schulz's, Miracle-Gro, or Hyponex. Those seem to be the most popular ones on the market. I have used all of them to satisfaction. For care, I suggest dividing it when it is dormant, which will occur later in the spring. Water thoroughly each time, allowing the soil surface to dry between waterings. Being a succulent, it propagates easily. Simply take cuttings in the fall and root them. Once it has finished flowering, it will be a challenge to get it to root again, as it has a low temperature requirement to do so (50 degrees). But even as a succulent without flowers, the plant is attractive.

And, as far as pronunciation goes, sound it out phonetically, and call it that. Who is going to argue with you?

Q: I have a tropical hibiscus plant that I purchased nearly five years ago. It was in a 6-inch pot but bloomed beautifully for about a couple of months. My cats ate it one day until there wasn't much left. I cut it back and hoped for the best. It has since grown back beautifully but has never bloomed since. I have put it outside during the summer and pruned it several times since. About two years ago I transplanted into a 10-inch pot. Last spring my mother, who used to work in a green house, cut it back drastically to help. It has grown back and continues to grow even during the winter but still doesn't bloom. It is on a table directly in front of a south facing window and is growing but never even produces buds. At the moment it is infested with white flies, so today I am going to try to wash those off. I read somewhere that blooms only appear on new growth not woody growth. Could I be pruning too much? My husband thinks I should get rid of it and buy a new one, but I am attached to it and just don't want to give up. (E-mail reference, Wichita, Kan.)

A: My best guess is that your hibiscus is not getting enough direct sunlight. It should be placed in a west or south window that gets direct sunlight at least some part of the day. It benefits the hibiscus to summer it outdoors as well. My next thought is the fertility. You need to be using a houseplant fertilizer that is high in phosphorus and potassium and lower in nitrogen. Hibiscus grow fast anyway, and anything with a high N content could almost put it in orbit growth-wise.

The plant can be pruned heavily, as it does flower on new growth, not the old. Get rid of the bugs by spraying with Insecticidal soap. That will knock them out and will not harm you or your family.

Q: I purchased a miniature orange tree about a month ago. At that time it was blooming beautifully and was very fragrant. That lasted about one week, then all the flowers dried up and started falling off. I've recently picked off all the dead flowers hoping that might help. When doing so, I noticed tiny white bugs crawling on the pot. What are these and do I need to be concerned? Is this why my plant is not doing well? (E-mail reference)

A: Those little white bugs could be mealy bugs, or some other critter that is up to no good. I suggest repotting in pasteurized soil, washing the roots carefully, along with the container. In fact, I would suggest immersing the container in a 10 percent chlorine bleach solution for a few minutes to make sure everything is clean or dead. Check the undersides of the leaves as well, and clean them with a damp cloth. Insecticidal soap will go a long way toward keeping many of the soft-bodied insects at bay.

Do you have a gardening or houseplant question? Write to Hortiscope, Box 5051, NDSU Extension Service, Fargo, ND 58105 or e-mail to Ron Smith at ronsmith@ndsuext.nodak.edu. Note to e-mail correspondents: please identify your location (city and state) for most accurate recommendations.

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Source: Ron Smith, (701) 231-8161, ronsmith@ndsuext.nodak.edu
Editor: Gary Moran, (701) 231-7865, gmoran@ndsuext.nodak.edu