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

By Ron Smith, Horticulturist NDSU Extension Service

Q: A few days ago, I finished reading the woody plants section in the master gardener handbook. The recommendation was (after digging the hole for a tree or shrub) to backfill the hole with native, not amended, soil. Why is native soil preferred compared with amended soil? (e-mail reference)

A: Native soil is better because it is the permanent soil the tree or shrub will be in. Amended soil alters the physical characteristics of everything around it, most notably the movement and retention of water and the air balance in the root zone. Native soil is the undisturbed soil of the local ecosystem. Any soil in the constructed landscape is altered somewhat, even though it is referred to as being native. Altered (designer soil) would be acceptable if done extensively enough. When the alteration is confined to the planting hole, it has the potential to be ineffective. Alterations can be in the form of extra sand and organic matter mixed for uniformity. This stratifies the soil profile, which causes problems, such as a very porous, well-drained soil in heavy, hard or compacted clay. This creates a perched water table in the planting hole. The homeowner typically is told to water his or her new planting two to four times a week, which in many cases results in anaerobic conditions in the root zone. This stresses the plant and kicks pathogens into becoming active. The plants either die or look stressed, so the homeowner adds even more water. This is something we all learned the hard way by having to replace a lot of plants. If the plant is going to make it, using native soil will do the job. If it isn't, using amended soil will not save it. If the soil is really bad, then modify the entire planting site down to a depth and width to allow the roots to grow and mature enough to support the tree without holding water in the immediate root area.

Q: I have a quick question for you about tree spacing. We would like to use Amur maples as a hedge in front of our house. I understand they can get tall, but can be trimmed back and kept to the size of a bush or tall hedge. I have seen some around town that are used as hedges and have a nice fall color. I read that the recommended spacing is 6 to 10 feet between trees. I would assume that is because you are planting it in a tree row and intend to grow it to full size. If I am planting the amur maples as a hedge and want them close enough together so they fill in to make a dense hedge with no gaps, how far apart should I plant them? Thanks for your help. (e-mail reference)

A: If you plant Amur maples 6 feet apart, they will make a nice dense hedge. However, you will have to keep them pruned to do so. If you want to accomplish your objective faster, then spacing the trees every 4 feet would be better. When purchasing the Amur maple, go for the hedge or multistemmed form. There are other plants that also would make an attractive hedge with good fall color, but are not as much work, such as the American cranberry bush viburnum.

Q: I've just been looking at your Web site and am wondering if you could help me. We have a rental property that has a number of weeping willows along the creek bank. The trees look stunning. However, we've just realized that all of the lower leaves and branches have been eaten by the horses our tenants have. I am devastated by this. Can you tell me if the leaves and branches will grow back to their former glory or are the trees permanently damaged? Any help you can give me would be greatly appreciated. (e-mail reference)

A: Horses do a good job of chewing things up, as many folks know! Whether they will return to their original glory depends on just how much damage the animals have done. Generally, willows are vigorous growers. Unless they receive a direct hit from an incoming missile, willows will survive and come back in pretty good shape. Horses can do other damage as well, such as compacting the soil under the canopy and scraping off the bark on the trunk. I would suggest temporary fencing to keep the horses from getting to the trees.

Q: I enjoy listening to your shows on Prairie Public radio and have called in once or twice. Thank you! I heard a question last week about coneflowers and would like to follow up with another question. I have a large cluster of coneflowers that I would like to move. Should I do it now before winter or wait until spring when they start coming up? Also, do you have any advice about the actual move? Do we dig them up in one big clump? (e-mail reference)

A: Coneflowers can be moved in the fall or spring. However, I prefer the fall season because there is not as much demand on the roots and aerial part of the plant at this time. Try to dig large clumps to get as much of the fleshy root system as possible. However, don't fret if some of the root is left behind. Thanks for following me on Prairie Public radio!

Q: I have a 20-year-old crown of thorns in my backyard. It grows tiny, white blossoms every spring. The thorns are about 3 inches long. Right now, it has small, golden-colored fruit that when cut smells similar to a lemon and has pulp and seeds like a lemon. We never have done anything special to this plant. We use it for making a crown for the cross on Good Friday. I can't seem to find a picture or description of this type. Are the fruits poisonous? Should I trim it every year at a certain time? Is it supposed to blossom throughout the year like some I read about in my research? I greatly appreciate any information you can give me. (Washington, D.C.)

A: First, congratulations on having a successful crown of thorns for so many years! You apparently are doing everything right with your plant, but I would in no way recommend eating the fruit no matter how much it smells like a lemon. The crown of thorns is in the Euphorbiaceous (spurge) family. While I cannot find any specific listing of any poisonings, tasting the fruit isn't worth the chance. Enjoy it for the rewards this plant gives you. There isn't a plant that can bloom all the time because even the most prolific blooming plants need a resting period to accumulate more energy.

Q: We have a large, very healthy silver maple. With our recent snow and ice, a group of branches became so heavy that the branches split. My husband thinks we need to prune all the broken branches off. I am hoping there is some repair or natural healing that will take place. Without these branches, the tree will look very lopsided. If the damage is deep, can the tree heal? Thanks for any advice. (e-mail reference)

A: The tree probably will not heal, but my answer is only based on what you told me. In cases like this, it is usually better to have the tree professionally removed rather than putting up with something that will not contribute to the aesthetics of your property. A tree will not regain the natural symmetrical beauty it had before the damage. However, you may want to get the situation evaluated by a local professional, such as an International Society of Arboretum certified arborist. To find one, go to

Q: How do I store my lily and calla bulbs? Everything I have read says to store the bulbs at 40 to 50 degrees. My garage is not heated, so I am afraid the bulbs will freeze if kept outside. My basement is heated, so I don't have a location that is in that temperature range. I do have a small dorm refrigerator that is not being used. I checked the temperature in it and the warmest it gets is 40 degrees. Is this too cold to store the bulbs? Do they need air circulation? Thanks for your help. (e-mail reference)

A: I'm afraid of condensation in the refrigerator causing disease or rot problems. The bulbs should have air circulation. Is there a corner in your basement that would be at least cool (lower 60s)? You could get away with that if needed and would be better than the options you mentioned.

Q: I have two schefflera plants that I have had for many years. I keep them outside during the summer on the shaded side of the house. The plants have prospered and are a beautiful green. I put them in my garage for the winter because I don’t have space for them in my home. Can I keep them on the side of my house throughout the year if I cover them during any frost activity? (Myrtle Beach, N.C.)

A: Only you know how cold it will get in your part of the country during the winter months. No problem if the worst is an occasional frost, but you have to provide adequate protection during that time. If you have prolonged periods of below-freezing weather, the plants will die. If you choose to leave them outside, be sure to put some mulch over the root zone in case a really cold snap catches you off guard. Often, when the top is killed off, but the root and crown are protected, the plant will generate new growth.

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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