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Hortiscope

Ron Smith answers questions about plants, trees and gardens.

By Ron Smith, Horticulturist

NDSU Extension Service

Q: I live along the Sheyenne River and use overhead pulsating sprinklers on my garden. Is this practice OK or would it be better to use a drip irrigation system? I raise pumpkins for my grandkids to sell in the fall. I have three garden plots and try to rotate what I plant in them. Last summer, the leaves on my pumpkin plants turned grey and wilted. By late fall, the pumpkins and squash appeared to be killed by frost. Is this from too much water or might it be a fungus? (Valley City, N.D.)

A: Change your irrigation to a drip system. The overhead irrigation is causing a fungal disease to develop as you describe. Other than normal crop rotation, I suggest staying with the same varieties, practice good site cleanup and avoid spraying.

Q: I would like to plant a windbreak south of our farm. The ground is alkali and runs along a ravine. What types of trees should I plant? My favorite choice would be Colorado blue spruce. Will it survive in alkali ground? We live in west-central Minnesota. (e-mail reference)

A: Colorado blue spruce would do well because it is widely adapted across North America. Ponderosa and scotch pines, plus Norway spruce, also would do well. I would encourage you to think in terms of plant species diversity because there is less chance of losing the entire planting should a particular pest move in and wipe you out!

Q: I have an apple tree that is about 17 years old. Generally, it produces a great crop of apples. Last year was one of the few years that the crop wasn't so plentiful. The apples were large, but almost all of them were covered with bumps that resembled pimples. They were not discolored. My wife took one to an Extension Service person who said the problem was bitter pit. I am looking up how to treat bitter pit on the Internet. The sites show pictures of infected apples, but none of them resembles the problem we had. Does this sound like bitter pit to you? If so, what is the best way to treat the problem? (e-mail reference)

A: You were given incorrect information. What you describe fits apple scab if the spots coalesced into velvety spots a quarter-inch or more in size and develop into corky lesions as the fruit matures. This is a fungal disease that can be controlled with good sanitation. That means removing all of the leaf debris and overwintering apples on the tree or ground. Spray this spring with a captan fungicide. Unless the apples were hit hard, the fruit is still edible.

Q: I have a huge row (28 of them) of rose of Sharon. They were planted in front of the house as a privacy hedge. Do they need to be pruned or cut? It looks like the tops were cut off at some point. (e-mail reference)

A: A shrub needs to be pruned only because of a perception by the viewer. If the plants or parts of the plant are dead or dying, pose a physical or visual hazard or are over-run with insect problems, then go ahead and prune. Another reason to prune is for the aesthetics or crop production if we are talking about fruit-bearing plants. There usually is no need to prune rose of Sharon shrubs unless one of these threatening factors exists. If you prune them, prune off all the tops. Selectively remove the oldest canes down to the base of the plant. Doing this through a sequence of years will keep the plant producing vigorous new shoots that you may find more attractive. It also produces a denser hedge and more flowers.

Q: We have a Canadian red cherry that I’m assuming has black fungus. I have attached a picture of it. The tree is 7-plus years old. Do you think it needs to be removed or do you think we can save it? If you think we could save it, please let me know what course of action I need to take. Our neighbor just had a beautiful, large Canadian red cherry removed because of black fungus. We live in Nebraska. (e-mail reference)

A: You probably can save it with spraying and pruning. However, with black fungus being rampant in your neighborhood, it would be a constant battle and you would be putting more pesticide into the environment than it is really worth, along with disfiguring the tree with the needed pruning to remove the black knots. I hate to tell you this, but I suggest that you have the tree removed and replant with something else. Living in Nebraska, you have a very wide array of flowering trees to select from as a replacement that would not be so disease prone.

Q: In the fall of 2007, I dug up all of my old strawberry plants because they had stopped producing as much fruit. I can't remember what variety I had, but I think they were Ogallala. During the spring of last year, I planted some Ogallala strawberry plants that grew well, but they would become over-ripe very quickly. I would need to eat or process them right away or else they'd get mushy. I would pick them when they were just right, but I couldn't even let them sit on the counter for a half-hour before they'd go bad. I didn't have this problem with my old strawberry plants. Did I get a bad strain of strawberry plants or is there something lacking in the soil nutrients or some other factor causing this problem? I'm wondering whether I should replant the strawberry patch again this year. Also, we live in Fargo and would like to plant ever-bearing strawberry plants, although I'm considering planting some June-bearing as well. Could you recommend some good varieties that taste great fresh or frozen? Finally, when the weather is very wet for an extended period, (several days), the strawberries tend to get bad spots on them. My strawberry patch drains well (raised bed with sand mixed in with the soil) and the bad spots are not from contact with moisture on the ground. Is this to be expected or are some varieties more prone to it? (Fargo, N.D.)

A: You probably didn't get the variety of strawberry that you ordered because that has not been my experience with Ogallala. I've grown glooscap and honeoye with some excellent results. I've also grown some cabot. They did well and had excellent flavor! All I can tell you is that if a strawberry variety disappoints you, then get rid of it! There are plenty of other varieties that will perform just fine under North Dakota conditions.

Q: I live in Fort Worth, Texas. I have a plum tree blooming, but it has been very windy, so many flowers are falling from the tree. Is that going to affect the amount of fruit? (e-mail reference)

A: Many environmental factors can affect fruit set, such as late frosts, rainy periods when the pollen is ripe and windy conditions when the pollen is ripening. If the flowers were pollinated before the windy weather came, you will get a good fruit set. The petals blow off when they are no longer needed as an attractant to pollinating insects.

Q: I received an alocasia Polly as a gift. Its leaves are starting to turn brown at the tips. Do you know why this happens and how I can prevent it from happening? There are many conflicting articles on the Web about how to care for them. Can you please tell me how to care for this plant? It is beautiful, so I want it to thrive. (Hettinger, N.D.)

A: In general, alocasia, while beautiful and dramatic to look at, is a challenge to have it thrive or even survive as a houseplant. It does best under tropical conditions with high humidity, warm temperatures with no drafts and moist soil. However, watering should be cut back during the winter months. If you can, try to give it a Gro-Lux light source or two, depending on how large it is, to get it through the winter. When frost-free weather returns this spring, move it outside under light or dappled shade and increase the watering regime. Good luck because I've not seen or heard of too many success stories with this particular species.

Q: I have a red delicious dwarf apple tree and a semidwarf Jonathan. Both trees are healthy. For the past two years, I have sprayed the trees after the petals have fallen and the apples are developing. I used Sevin and an orchard insect spray to prevent an apple maggot infestation. I followed the directions, but within a week all of the apples fell off and it looked like the leaves were burned. Any suggestions on what I am doing wrong and recommendations for a more successful approach this year? (e-mail reference)

A: Apparently, the mixture of the orchard spray and Sevin are proving to be toxic to the developing apples. I would suggest just using the Sevin insecticide to control the maggots, but follow the directions. Other possibilities exist. Your problem could be residue in the sprayer from another product. The temperature may have been too high at the time of application. The Sevin could be acting as an embryo aborter for this particular apple cultivar. You might want to try an alternate insecticide, but use a clean or new spray applicator. Spraying at petal drop is the correct approach. Be sure to follow label directions for subsequent applications. The intent of the spraying is to leave a small residue on the foliage to take advantage of the feeding habit of the female maggot fly as she licks up the moisture on the foliage and young fruit. In order for the timing to be right, you might want to get a sticky trap or pheromone trap to indicate the presence of the flies in your trees. Be sure to follow good sanitation practices by picking up all the fallen apples because this is where the pest originates. If you leave the fallen apples, the pests pupate in the soil during the winter, emerge as adults through the early summer and lay eggs just under the skin of the apples.

Q: My neighbor has a buckeye tree in her backyard. Her grandson was raking and I walked over to talk to him and noticed a buckeye nut that had sprouted in the leaves. I took it and planted it in a pot. The buckeye seemed to be growing well until a week ago. The tree had been growing for about seven weeks. The leaves have started to wilt. Please tell me what I can do to bring it back to life. The tree has been growing indoors the entire time. I have grown fond of this tree and have plans to transplant it. (e-mail reference)

A: Unfortunately, I don't think it is possible at this point. What you should have done is allow the seedling to stay outdoors in its pot and in the ground until you decided where to plant it this spring. After doing a little math, it must have been around the Christmas holidays when you rescued the seedling from the leaf raking. My guess is that you live where the weather is comparatively pleasant during the winter months. As a desperate measure, I would suggest moving the seedling outdoors and hope it recovers. These temperate, deciduous trees need to go through the seasonal cycles to survive. Keeping it indoors may sound nice, but it isn't what the plant needs to survive or thrive. If you lose this one, you'll at least know better the next time.

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 ronald.smith@ndsu.edu.


NDSU Agriculture Communication

Source:Ron Smith, (701) 231-8161, ronald.smith@ndsu.edu
Editor:Rich Mattern, (701) 231-6136, richard.mattern@ndsu.edu
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