April 10, 2003

Hortiscope

Ronald C. Smith, Horticulturist
NDSU Extension Service

Q: I recently bought a plant from a florist who said it was a hoya. It has leaves like a hoya, but the blooms are not starlike. The end of the stem has six blooms which are shaped like a long skinny bell and are yellow turning into an orange color. Two of the six are in bloom now. The card stuck in the soil said it was a black Pagoda. Do you know if this is or is not a hoya plant? (E-mail reference)

A: What you describe sounds like a hoya, but I cannot find a match for black Pagoda. That doesn't mean anything however, because new introductions appear faster than one can keep up with them. If you trust the florist, then it is probably what you were sold.

Q: My lilac bushes (probably 20 years old) not only have powdery mildew, but also have moss growing all over the lower branches. What type of product should I purchase to solve the problems? (E-mail reference)

A: Improve air circulation and light penetration for the shrub via selective pruning. The humidity is too high and direct sunlight is too low. The moss growing on the lower branches will not hurt anything but is indicative of the conditions I mentioned. Buy a product put out by Schultz called Fungicide 3 which is a neem tree extract. It does the job of controlling mildews and other fungi along with being a decent insecticide and miticide. It should be available at your local garden supply stores.

Q: I have owned a crown of thorns plant for about four years. It seems to be doing very well. However, it is very tall and I wonder if I should be cutting it back? (E-mail reference)

A: Cut it back to an acceptable lateral branch, then spray the cut end with cold water to arrest the flow of the latex sap. You might take the top three to four inches of the cut stem and try rooting it, after allowing the ends to dry for a day before placing them in a 50/50 mix of peat/sand.

Q: I have made new tubers on my gloxinia with a leaf and transplanted into a pot, however it seems that I have two or three plants growing from the one tuber. Is there a way I can separate them? (E-mail reference)

A: I am assuming you mean the florist gloxinia. My references indicate that this is not one of the procedures for propagation. If you want to risk a possible sacrifice, then carefully cut a piece of the tuber with a plantlet attached. If it succeeds, then you have found another way to propagate this species.

Q: I purchased two plant bulbs that came with instructions and two glass vases. I placed clear stone in the bottom and filled with water just below the bulbs. They bloomed once (one each bulb) and the leaves grew to about 18-22 inches but then started to droop and the blooms disappeared. Can you please suggest a solution? (E-mail reference)

A: It sounds like you purchased some paper-white narcissus bulbs which have done exactly what they were supposed to do. You can either throw them out or transplant them outdoors in a protected spot and hope they come back next year (Not very likely around here!).

Q: We have recently cut down our lilac tree and are now trying to get rid of the root bowl. We favor digging it up so that we can replant quickly. However, it is very large and it already has taken several days of digging and is nowhere near half done. Also, it has been suggested that the roots could re-sprout using this method. If we had the roots treated, how long would it be before the root bowl rotted down enough for us to re-plant? If treatment is the best method, who would you recommend? (E-mail reference)

A: I would suggest hiring a tree service company that has stump remover capability. They will come in with a grinder and turn the stump into sawdust, along with any roots they can reach. Save your back (and possibly your marriage) and have a machine do the work! Sprouting from the roots that remain - you cannot get them all out - will occur if the plant was alive at the time of removal. That can be controlled with a simple broad-leafed herbicide is used to control dandelions in a lawn. The natural rotting method could take years and you would still get sprouts.

Q: My hollyhocks are beautiful and plentiful -- too plentiful. I have tried to remove the seeds but it is impossible to get them all. The flowers are out of control. They keep re-seeding themselves in all my flower beds. I tried to keep only one or two but when I tried to remove them, it was like trying to remove a small tree, with the trunk as big as my arm. I used Roundup to kill the plants but the plants kept growing, not where I applied the Roundup, but from the roots around the main plant. I tried to dig them up by digging down at least a foot and six inches around the plant trying to get all the roots. However, they keep coming up. The hollyhocks have invaded my iris beds and I can't kill the hollyhocks without killing the iris. Please have a solution for me. (E-mail reference)

A: Hollyhocks are usually biennials, which means that they will bloom in the second year of growth. If you can get to those that are just rosettes this year, they should dig out fairly easily. If you happen to be unfortunate enough to have only durable, perennial hollyhocks, then the use of a herbicide that controls dandelions or broadleaf plantains will work. You need to either remove or cover the iris prior to spraying or else they will be negatively affected by the herbicide. These are the best suggestions I can come up with. I'm surprised that the Roundup didn't do the job. Try using a wetting agent with your herbicide this time. You may have to apply it more than once.

Q: I planted ten evergreen arborvitae along a fence line for privacy about three years ago. The first year one died, but I replaced it. The second year they all took off. Coming out of this winter, all the plants have massive interior leaf loss. The exterior of the plants have a hint of brown. The tops were also fanning out so I bound them with some twine to straighten them. Did they not get enough water going into the winter? We had a drought followed by a brutal winter. Can they be saved? Is there such a thing as too much water for them? (E-mail reference)

A: Interior foliage death is not unusual considering the weather conditions leading up to the winter. As long as the exterior portion of the trees are alive, they will prevail. The hint of brown is normal at this time of year. Just don't allow them to become drought stressed this coming growing season, and equally important, don't drown them in water either!

Q: I have a 150 inch long wall of arborvitae along my property. They are approximately 80 inches tall. I would like to trim the height back to 72 inches. Can I do this without harming the shrub and when is the best time of year do it? . (E-mail reference)

A: The arborvitae can be pruned anytime - spring, summer or fall, as long as all of the wispy green growth is not removed. If you cut back and remove all the foliage in a spot, that spot will be there forever! These are one of the few woody plants that respond well to shearing. Just be sure to try and maintain the natural shape.

Q: I have several Ohio Buckeye seedlings. How long before the trees produce seeds? Also, what is a good fertilizer for the trees? (E-mail reference)

A: They will start producing seed when they begin flowering, which should be in three to five years. Most trees don't need fertilizer but if they do, very little. A 10-10-10 material is usually used.

Q: My friend and I are having a debate over whether a tomato is a fruit or a vegetable. Can you please answer this question for me? (E-mail reference)

A: Tomatoes are fruits eaten as vegetables. Here's another one for debate: rhubarb is a vegetable eaten as a fruit.

Q: I have an African violet that is in need of repotting but it looks like there are two tubules coming from the soil. Can these be divided successfully and how do I separate them? (E-mail reference)

A: Yes they can be divided using a sharp knife.

Q: I have been looking for a spray to fight apple tree maggots. The material that I had last year was a liquid that was mixed with water and sprayed on the apples while the apples were small and the moths were present. As I recall, I believe it had the chemical substance Diazinon. I was told that this substance has been taken off of the market. I have an advanced degree in chemistry so I checked several references that I have. It is a somewhat toxic material if not handled properly. What can I use in place of this material and where can I purchase the material? I do a late summer and fall clean up of the apples that have fallen to the ground. However, others in the neighborhood do not do a clean up. (Faulkton, S.D.)

A: You are correct in your findings. Actually, apple maggots lend themselves quite nicely to pheromone control. If you have a good garden center or garden supply store in your area, they will likely have pheromone traps that you can hang in your tree (I suggest three per tree the initial year) and will catch the adult male preventing copulation and resulting offspring that will damage the apples. That same garden center may also have false apples that are covered with a sticky substance that holds the insect there once they land on the surface. No control, either chemical or organic, is 100 percent effective. But I have found that these two methods do an excellent job of greatly reducing the number of affected apples -- along with good sanitation practices like you say you are following. And of course, you don't put any toxic chemicals into the environment!

Q: The bark on the trunk of my apple trees has come off over the winter and there are little holes bored (almost in alignment) on the trunk of these trees. Can you tell me what to do? (E-mail reference)

A: I'm willing to bet those holes that you describe are from the yellow-bellied sapsucker. Apple trees, among others, are a favorite for these very beautiful, but sometimes pestiferous birds. Unless their damage is extensive and they return each year to the same tree, healthy trees can usually handle any damage they do. I have a birch tree in my yard that is visited each year by these characters but it has survived, thus far, without noticeable damage. Control is often impractical -- spreading sticky or tangle foot material on the bark where their feeding is most frequent. You can also attempt scare tactics which sometimes work. But unless your tree is already weakened, it should recover nicely.

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: Rich Mattern, (701) 231-6136, richard.mattern@ndsu.nodak.edu