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Ron Smith answers questions about flowers, trees, gardens and shrubs.

By Ron Smith, Horticulturist

NDSU Extension Service

Q: When I was growing up in North Dakota, there were a lot of plum trees in shelterbelts. The plums were little and purplish with some yellow. The flesh of the fruit was yellow. These plums seemed prolific and hardy. I loved the very sweet, juicy flavor. These plums were great for eating and in jams. Any idea what they might have been? I would love to plant some. I live in central Minnesota very close to St. Cloud. Our soil here is sandy because we are on the ancient banks of the Mississippi. (e-mail reference)

A: You must be referring to the native species called the American plum (Prunus Americana) because it has the characteristics you describe. Be aware that it is valued in shelterbelts because it tends to sucker, which I am sure it also will do in a landscape planting.

Q: What is the lowest temperature that a spider plant can live in? I have a spider plant that has been in my family for the last thirty years. (e-mail reference)

A: Spider plants can probably survive for some time with the temps between 45 to 55 degrees. It will be killed by any freezing temperature. Spider plants thrive in tropical or semitropical conditions, so a plant will fare pretty well in a home with a temperature of 70 degrees during the day and 60 degrees at night.They rebound if the owner summers them outdoors in dappled shade.

Q: I have a silver maple that I pruned pretty heavily last fall. Now I see a large branch that I also wish I would have pruned. Can I still prune it this winter? I’m concerned about when the sap starts running. Is next fall time enough or the best time to prune the larger branch? (Perham, Minn.)

A: Sap will flow, but it should not be a detriment to your tree. You need to ask yourself if it is absolutely necessary for you to prune that large branch at this time. It would be better to see how the tree responds to your heavy pruning from last fall before going ahead and removing the branch. In the fall, everything is shutting down which includes a tree healing its wounds. You are better off to wait until the tree fully leafs out and then giving it a pruning (probably in early June). There is still active growth going on at that time and much faster and effective wound healing.

Q: I would like to start some vegetables inside the house to transplant to my garden this spring. When would be a good time to plant or start them inside? Do they need any special soil and potting mix? I have no idea because I have never tried this before. Any suggestions or ideas would be greatly appreciated. (West Fargo, N.D.)

A: Basically, vegetable crops can be divided into two very broad categories. These are warm- and cool-season crops. Cool-season crops, such as cabbage, broccoli, cauliflower and lettuce, can be started and transplanted earlier than warm season crops. Warm-season crops, such as tomatoes, peppers and eggplants, should be started indoors about four to six weeks before moving them outdoors. Everybody always likes to be given a specific date to do that, but with the fickle weather patterns we go through, back those planting dates up from the last average frost date. So let's pick May 17 just for practice. Backing up from that date would take us into about April 1 to start peppers and about April 17 for the others. Of course, when May 17 rolls around and there is no sign of reasonable gardening weather, then keep them indoors for another seven to 10 days before setting them out. You can set cool-season crops out when the frost is out of the ground and the soil can be worked because they are tolerant of lower temperatures and light frosts. Always use a pasteurized media when starting seeds indoors. This helps head off lots of potential problems with diseases. Make sure the water being used is at room temperature and not directly out of the cold water tap. My wife uses distilled or reverse osmosis water to get the seedlings up fast. She also uses a mister to wet the media. The lack of salts in these water sources promotes faster germination. Keep the media damp, but not soaking wet. Light energy is very important! Using fluorescent lights is an effective and inexpensive method. The light needs to be stationed just inches above the seedbed. As the seedlings emerge, the light needs to be raised so that it is 6 inches above the tips of the plants. Warm the soil using temperature controlled heating cables and cool air. Temperatures around 60 degrees will produce ideal seedlings that have extensive root systems and stocky, strong tops. Make sure the lights stay on for 12 to 16 hours per day. For more information, go to

Q: I inherited a fern when my grandmother passed away at age 98. It was handed down in the family, so we estimate that the original plant was about 100 years old. I believe it is a lace fern. It is similar to a Boston fern, but with very finely-frilled leaves. For the first two years I had it, the fern was vigorous and it sent out many offshoots. I divided it several times to give to other relatives. Now I am afraid that my fern has a scale infestation. I accidentally brought home an infested plant and have found scales on my other houseplants.

Sections of the fern have withered and the leaves have dropped. I threw out a couple of the infested plants and treated all the others (including the fern) with insecticidal oil. I used Safer Soap a month later. My other houseplants now seem to be doing OK, but I can't tell if the fern is doing any better. It has some areas that look fine, but some leaves have continued to wither. Of course, because it has sentimental value, I am worried about it. Should I treat it again with something else or is that going to do more harm than good? Could the plant be withering because of something else, such as dry air? (Chicago, Ill.)

A: If the treatment was effective on the other houseplants, it is a pretty safe bet that it also was on the fern. I would suggest getting a humidifier and moving it close to the houseplants, especially the fern. This plant is native to a very humid environment, which our homes in the north during the long winter months are not. If this plant should succumb, I would suggest going to one of the friends or relatives that you gave a part of this plant to and see if you can get an offshoot started from one of those.

Q: I had a croton last year, but it died due to the lack of care. I have pulled it up, but wonder if it would it come back to life if I replanted it. (e-mail reference)

A: If the croton died, it will not come back to life. To see if it did die, scratch the stem and see if the tissue is still green beneath. If so, then there is a chance. If not, all the magic and cultural input will not bring it back again.

Q: Last summer, my tomatoes had blight. I think it was early blight because the leaves yellowed, had brown spots and died. Then my pole beans, which were planted in an adjacent raised garden box, started getting rusty and brown/black spots on the leaves. The bean plant leaves started to die after that. Is there a blight that affects both beans and tomatoes or am I dealing with two different problems? Is the blight from the water splashing off the soil? If that is the case, will placing newspaper or plastic around the tomato plants be helpful? (Pelican Rapids, Minn.)

A: You are dealing with two different disease organisms. One is bean rust that is caused by the fungus Uromyces phaseoli typica. The disease is most important on dry and pole snap beans, but it also affects bush, snap and lima beans. Bean rust normally occurs in late summer. The fungus exists between crops in the form of spores that infect the following crop. Cloudy, humid days with temperatures between 60 and 75 degrees are favorable for disease development. Under these conditions, an infection of bean rust can produce a new crop of spores in 10 to 15 days. Although the spores may blow long distances and infect plants where no beans have ever been grown, it has been shown that when one crop of beans follows another in the same field, the amount of rust inoculum is increased. This means that the following crops may be severely damaged. A good crop rotation is the first suggestion for control. Don't plant beans in the same location for another three years. Spraying with approved fungicides at regular intervals, starting when the disease first appears, will give you effective control. Some bean varieties are resistant to some races of the rust fungus.These varieties are listed as rust resistance in seed catalogs. Consider them where space doesn't permit long rotations and where fungicides will not be used, especially in late summer plantings. Basically, the same holds true for tomato problems. Select resistant varieties and alternate your plantings in three year crop rotations. Should the symptoms begin showing again, immediately remove the infected plant. As for watering, it is best if you employ a basic drip system to avoid any splashing and overwatering possibilities. Also, some common sense will help. Don't work the crops when the foliage is wet from morning dew and keep weeds at bay. Open up the area around the garden by pruning trees and shrubs to allow for better and longer sunlight penetration and air circulation. Finally, with any garden vegetable plantings, work the soil up every spring prior to planting to improve the drainage.

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

NDSU Agriculture Communication

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