August 30, 2001

Hortiscope

Ronald C. Smith, Horticulturist
NDSU Extension Service

Q: I raise African Violets under lights and recently have been losing them. The center leaves get hard and they stop blooming. Is this an insect or disease problem? Also, I recently purchased a tamarix shrub from a nursery and wonder if it will be the salt producer you mentioned in a recent article. (Scranton, N.D.)

A: African violets often decline when they are not divided on a regular basis, and that may be the problem in your case. Disease is also a possibility -- crown rot, from too much water or the crown remaining wet too long. Yes, I am afraid the tamarix (also known as saltcedar) is now on the no-no list. From what I understand, it creates a monoculture of its own species over time.

Q: Enclosed are samples from my rose plant and my tomatoes. Can you tell me what is wrong with them and what to do to cure it? (Jamestown, N.D.)

A: The roses have a severe case of black spot fungus, quite common on roses, especially with the weather we’ve had. Correct by cleaning up all fallen leaves and removing any infected leaves remaining on the plant. Spray with Schulz’s Fungicide3 to prevent recurrence. The tomatoes are devastated by bacterial blight, and at this stage of the season it is not worth doing anything about it. Next year, select resistant cultivars, plant in a new location and keep irrigation water off the foliage.

Q: I have 10-year-old poplars in my yard that have developed warty looking growths. Can I do anything about it or are the trees doomed? My black walnut has produced nuts for the first time this year. Will they mature before the frost hits? (Amidon, N.D.)

A: The growths are nothing to be concerned about. They are simply stem galls caused by insects or mites laying eggs earlier in the season. This action causes the plant tissue to proliferate around the egg and larvae. Other than spoiling the possible aesthetics of the tree, they cause no serious harm and do not need any action taken against them. Your black walnuts should mature. They do in other parts of the state.

Q: Enclosed is a leaf from my hydrangea. Can you tell my why the leaves on the bottom are turning black and have holes in them? They are planted on the north side of my house. (Oakes, N.D.)

A: The leaf you sent showed symptoms of hydrangea leaf spot fungus. Clean up the leaves well this fall, prune heavily and spray with Bordeaux mixture next spring as the leaves unfold. Concerning the holes in the leaves, they could be caused by any number of leaf-eating insects. If they are not now present, don’t worry about them. They’ve moved on to more succulent plants.

Q: Enclosed is a leaf sample from a maple tree we planted two years ago. The small new leaves are drying up and shriveled as you can see. The large leaves are okay. What can I do so the whole tree doesn’t get infected? (Kulm, N.D.)

A: The leaf sample you sent showed classic symptoms of herbicide damage. It should outgrow the injury if the dose wasn’t too strong.

Q: I have a schefflera tree which is about 20 years old. The main trunk-stem is about 5 feet tall without any foliage. The top 2 feet has stems with leaves. I would like to cut it off about 6 inches from the bottom. Would it grow new leaves? (Springfield, S.D.)

A: In almost all cases I can recall, simply cutting back the Schefflera back resulted in new growth emerging. Make a straight cut with either a knife or pruner 6 to 9 inches above the soil line. Water and fertilize as normal. In about four to five weeks some new growth should be evident.

If it doesn’t re-grow, that is simply an indication of a very weakened plant.

Q: We have a grove of trees along the west and north of our farmstead. Most are elms, cottonwoods and boxelders. The recent winds and not ever pruning them has taken its toll. What I would like to do is clean out the dead ones and trim what needs trimming, then plant replacements. The sunshine that reaches the floor of the grove is very limited. Are there any trees that can grow with less sunlight? (Aneta, N.D.)

A: Many trees will grow, but weakly in the sub-canopy light of your grove. I suggest looking at the very species you are currently growing, the elms and boxelders in particular, as they appear to have the ability to grow under such conditions.

Q: An oak tree in our yard fell over ( no wind). It was huge and old. The leaves were very green and healthy. It looked like the inside had rotted out. I couldn’t find any insects except ants living in the decayed matter. Will our other trees become rotted like this one? (Kerkhoven, Minn.)

A: Yes! I suggest contacting a forester or arborist to have an increment boring carried out ASAP. The internal rot is not unusual on older trees, often with no visible symptoms.

Q: Enclosed are a couple of branches from my pine trees. This developed in the last three to six weeks. Some branches are all bare. This covers as much as 20 percent of some trees; 75 percent of the trees show no damage. Please advise. (Wing, N.D.)

A: I could not detect any insect or pathogen activity on the samples you sent. I think what has hit your pines is some kind of environmental stress, which is weather related. This resulted in the death of some bud and needle tissue, giving you the odd pattern of dead or dying needles. Ponderosa pines are nearly indestructible, so I don’t think you are in danger of losing these. Just continue to monitor them to make sure nothing else moves in and adds to the problem.

Q: I'm doing this simply for the fun of it. I was eating a peach, don't know which kind exactly, but whatever you'd commonly find in the grocery store. When I got to the pit, I noticed it was cracked and there was just a hint of green sprout on the internal seed. I took the seed out and placed it in a styrofoam coffee cup, in regular potting soil, by a window which gets sun from about 3 p.m. on to 7 p.m. at current summer hours. It is in a room which is at regular room temp for most of the day (70 give or take). I keep the soil fairly moist, watering a bit once daily. Do I have any hope of getting this to sprout out? Any recommendations on how to continue? (E-mail reference)

A: I like hearing from an inquiring mind. Peach seeds need a cold stratification. You didn't say how long you had the seed in the cup, but if it hasn't been too long, take it out and move it into the crisper (where you would store lettuce) in your refrigerator for about 90 days, planted in damp unmilled sphagnum moss. The embryonic root should be emerging by then if the seed is alive. Plant the sprouting seed where you want the tree to grow outside. Otherwise, simply plant the peach seeds outdoors in the soil this fall and let mother nature provide the cold treatment.

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