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

By Ron Smith, Horticulturist

NDSU Extension Service

Q: In your column, I saw a letter about hornets or wasps eating honeycrisp apples. You suggested getting an exterminator, but I don't know where the nest is. They've come every year and decimated the apples on the tree. Any suggestions other than sugar water in plastic bottles? (Fargo N.D.)

A: Your best defense against these stinging pests is to get traps that can be hung in your tree. The wasps or yellow jackets (likely culprits) are attracted to the aroma coming from the trap. They go in the traps and cannot get out. It is "sweet revenge" for all the stinging they have done. It will not stop them completely this late in the season, but it will reduce the problem. Next year, put the traps out about a month earlier. Set two to four traps per tree, depending on the size. This will get them started earlier and bring down the population substantially. If you can locate the nest (usually in the ground), you can have an exterminator take care of the problem in a matter of seconds.

Q: I just planted a lawn two weeks ago. So far, everything is coming up well. When should I fertilize for the first time? Keep in mind that I did not put a starter fertilizer down. I have a 60 percent blue grass and 40 percent rye and fescue mixture. Is this something that should wait or is it OK to put a little fertilizer down? I have a 60,000-square-foot yard. (e-mail reference)

A: You can fertilize after you have mowed the grass at least two to three times. You can fertilize in the middle of October unless you live where you'd be covered with snow or the soil is frozen. Fertilizing will benefit the grass this fall and next spring. An acre and a half of grass is a lot to mow and fertilize! While I'm all for a grassy landscape for beauty and play, the mowing of that much grass is no longer fun for me.

Q: I was given a Miss Kim lilac bush for Mother's Day. It gets plenty of water but not standing water. Our soil is very hard clay, but we have fertilized and mulched around the base of the bush. We also made sure the planting hole was big enough to give the roots plenty of room. However, it was green for only a couple of weeks and then looked like it was in need of water. The leaves are curled and browning and there are little, white dots on the stems. I don't really know if the dots are normal. I had trouble with this same type of bush at our previous house. What is wrong and what am I doing wrong? (e-mail reference)

A: I don't think you are doing anything wrong based on what you are telling me. I’m assuming you have it sited correctly in an area that gets full sun but is not baking on a southside brick wall. Another point is to check the planting depth. Many folks plant too deeply, which ends up causing the problems you describe. The white dots could be oyster shell scale, which could spell trouble. Carefully scrape one off with your thumbnail to see if there is a little critter under it. If so, this would require a systemic insecticide, such as Orthene, to bring this pest under control.

Q: I have a flowering crab apple tree. It has partially bloomed two extra times this year. Is it because of our unusually cool weather? (e-mail reference)

A: The flower buds have a chilling requirement that releases the buds from dormancy to bloom. Sometimes a hormonal (florigen) imbalance results from the combination of shortening day lengths (photoperiods) and cool weather. The florigen, which is produced in the leaves, will trigger this partial blooming to take place. Not much more is known about this influential hormone, so research breakthroughs are on the horizon for us! Thank goodness this doesn't happen on a wholesale basis or our food supply would be in jeopardy!

Q: We have a beautiful, old silver maple in our backyard that is at least 20 to 30 years old. Roots have surfaced in many locations, so I am concerned about damage from mowing. Is it harmful to add soil and mulch around the tree? We are thinking of about 6 inches of soil and a few inches of mulch. We would taper everything down as we get to the trunk to prevent any rot at the tree base. However, I have read that covering roots is a bad idea. Any help you can provide would be appreciated! (Stone Ridge, N.Y.)

A: Based on your description, I would say that you could put that much well-drained soil around the tree. These large, woody support roots usually are not the ones that suffer from being covered. What suffers are the fine hair roots at the extreme ends of the root system. This is where the active transport of water and nutrients takes place. The process requires oxygen, so any excess soil applied outside the drip line will have the greatest potential of killing the tree.

Q: I purchased a jade about a year and a half ago. After a season of soft, dropping leaves, it has doubled in size and has a lot of new growth on the branches. It has three large trunks with three branches each. It also has many stems and leaves. What are the rootlike growths from the stem just below the leaves? I just noticed it today. I plan to repot it next spring because two of the large branches are beginning to rest on the pot. Any suggestions? (e-mail reference)

A: What you are seeing is known as aerial roots. It is common in a jade’s native habitat, but rare in home locations because of the lower humidity. Apparently, this jade likes your household air moisture! Don't be afraid to prune and give it more light. In an interior environment, most houseplants don't get any exercise from movement with the wind and rain. This causes a plant to have weaker stems and trunks. It also is sometimes caused by low light intensity and duration. I suggest pruning the jade to lighten the load and then get a small oscillating fan on a timer to give the plant a little movement. Finally, set a plant light on a 12-hour timer to give it a boost of light energy!

Q: I have about 15 peony plants. Some have been in place for about 13 years. The older peonies are becoming bushy, but are very healthy looking. How do I know when to split them and how is that done? (North Carolina)

A: It is time to divide the plants after 13 years in the same spot! The middle of September through early October is the preferred time to lift and divide many perennial flowers, particularly spring- and summer-blooming perennials, such as peonies, iris, bleeding heart, hosta and coral-bells. If divided in the fall, they'll still have time to re-establish before blooming next spring. If divided in the spring, on the other hand, they may not bloom well until the following year. Use a sharp garden spade to lift your perennials. Dig several inches out from the outer stems and lift the clump out of the ground. Then divide the clump into sections. With peonies, cut the root clump into sections that have at least three or four eyes. Be sure to use a sharp knife and leave one of the long roots attached to each piece that has an eye on it. Don't divide peonies more than once every three years. Iris plants should be divided every four years or so. Lift the clump out of the ground and cut the leaves back to about 6 inches. Dividing the clump depends on how tough the roots are. Try to damage the fewest roots possible. How deeply you replant also is important. Plant peonies and irises so the top of the root or rhizome is no more than 2 inches below ground level. If you plant them too deeply, especially peonies, they may not flower. Adding a handful or two of bone meal to the planting hole will help your divisions re-establish. It also is a good idea to sprinkle a little fertilizer (5-10-5 or 10-10-10) on the soil surface after filling the soil back in the hole. This will slowly work its way into the root area.

Q: I have three 10-year-old cottonwoods in my backyard. This spring, one of the three failed to fully bloom and has sprouted a sucker in the neighbor’s yard. I am wondering if the sucker is stealing the nutrients from the host tree. If so, should the sucker be cut down? (Arizona)

A: This is known as adventitious growth. It is a common problem with certain tree species. Cottonwoods are leaders at producing them. While they may be bleeding nutrients initially, they eventually become contributors to the overall production of photosynthesis. The mother tree is going through a decline of some kind, such as vascular wilt, borers, cankers or root problems. Contact the county Extension agent where you live to see if he or she can offer some clues as to what is going on.

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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