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Ron Smith answers reader's questions about the world of plants, trees and gardens.

By Ron Smith, Horticulturist

NDSU Extension Service

Q: I have a walnut tree that was hit by lightning and cracked down the middle. I was told we can not burn this wood to heat our house. Do you know if we can burn it? (e-mail reference)

A: Every forestry source rates black walnut as a good, clean-burning firewood, with a pleasant aroma. The only complaint is that the British thermal units produced are not as high as with elm logs. Although not the best use of this esteemed wood, you can burn it without undue concern.

Q: I have wonderful raspberry bushes that I transplanted following your great instructions. The bushes will have full sun from noon on, but no early morning sun. The bushes were transplanted into mulch. Is this going to work? I have to pick the fruit before my golden retriever does. (e-mail reference)

A: A golden retriever that likes raspberries? That's a new one! The bushes should do OK with direct sun from noon on.

Q: A woodpecker has made a hole in our apple tree. Should I fill the hole with something? We have plugged the hole so the bird cannot continue drilling. We would appreciate any advice you can give us. (e-mail reference)

A: There isn’t anything you can do about it except keep the hole covered. Hanging aluminum pie pans in the tree will help keep woodpeckers from showing off.

Q: I was reading your answers on poplar trees. Is it possible to transplant the suckers? If so, what would be the best process? (e-mail reference)

A: The best time to transplant is while the trees are dormant. Dig up as much of the sucker and root as possible. Plant the trees and water in well, and they should grow for you.

Q: I’ve had two cranberry viburnum bushes for three years. They are very healthy and have set their buds for spring. I live in northeastern Wisconsin. My problem is that they never have blossomed, so I never get any fruit. Any suggestions would be appreciated. (e-mail reference)

A: You might be giving the bushes too much tender, loving care. Try driving a straightedge spade into the soil about 2 to 3 inches from the plants when the frost leaves the ground to see if that stimulates them to flower next year. Do this in at least three places around each shrub.

Q: I came across your Web site while trying to find some answers about my jade plants. I bought two small jade plants in December. I repotted both plants and they seemed to be doing well in their new home. I water them when the soil is dry and they get a good amount of (indirect) sunlight during the day. They are slowly growing and all the branches have been sprouting new leaves. However, during the past few weeks, some of the branches on both plants have been losing leaves. The other branches have been continuing to thrive. Any advice for me? (e-mail reference)

A: This is probably an adjustment the plants are making to the new household environment. There is enough light to generate some new growth, but not enough to maintain the old. I wouldn't worry as long as it continues to show new growth this spring and the defoliation doesn't accelerate.

Q: I have been trying to eliminate oxalis from my perennial gardens for the past three years, but have not been successful. Do you have any suggestions? (e-mail reference)

A: Oxalis is tough to get rid of because of its very high seed production and the high viability of that seed. There are two weapons in the arsenal to control this pest. Triclopyr (Turflon) can be applied as a pre-emergent and any 2,4-D products can be used as a postemergent.

Q: I was looking up your extremely helpful hints on care for spider plants. I seem to have noticed a common theme. People seem determined to put plants not meant for fish in fish tanks. People seem to think the decorative value overrides the safety of the living creature. I strongly urge people to look up aquatic plants for use in fish bowls and tanks and leave the houseplants in flowerpots and hanging baskets. People should consult with a reliable aquarium source to find out what plants are toxic to fish. The latest fad for houseplants involving a fish is a peace lily/betta fish combination. The combination is a somewhat safe foray into keeping houseplants and fish together. However, many gift shop owners selling these kits tell the buyer that the betta does not need to be fed because it will eat the roots of the peace lily. This advice isn’t close to the truth. A betta is a carnivorous fish and needs fish food made especially for betta fish. The only reason a betta will eat peace lily roots is because it is starving. If you're never fed, you eat what you have to. I have owned hundreds of these fish over the years. Many of the fish were victims of the peace lily vase, but nursed back to health from starvation and from toiletlike water that was never changed. Many people are told never to clean the water because the plant will do it. No! Change two-thirds of the water once a week, and feed your betta twice a day. Also, the tray at the top of the vase that often is filled with marbles keeps the betta from getting air. Eventually, the plant's roots will die and then release toxins into the water that are harmful to fish. Please don't ask bettas to sacrifice their lives to enhance someone's decor. Here is one of the best sites I could find with more information. The site is at (e-mail reference)

A: Thanks for the information on the plant/fish combination. I'm sure the readers will appreciate this insight and the Web site you provided.

Q: I want to plant red twig dogwoods to be used as a hedge along the side of my house. Will the dogwoods harm my foundation? How far from my foundation do I need to go to plant the seedlings? How far apart should they be planted? (e-mail reference)

A: You have nothing to worry about concerning the foundation of your house. However, be sure the dogwoods are planted outside the drip line of your roof so they get the benefits of rainfall events. I would suggest a spacing separation of about 3 feet.

Q: I have a very large, old cottonwood tree on my property that a hungry flock of cedar waxwings roost in every year. I was bird watching yesterday and noticed them eating something from the top of the tree. The tree is very tall, so even with binoculars I could not tell what they were eating. I looked at the branches low to the ground and did not see anything that looked remotely edible to a flock of birds. Do you have any idea what they could be eating? There is mistletoe growing at the top. I have not read anything about waxwings eating mistletoe. (e-mail reference)

A: Cedar waxwings love berries and will wipe them right off of any shrub or tree. The presence of mistletoe with berries would be the answer. The birds are nonselective eaters, so any berry source will do. They have appetites like growing teenage boys!

Q: My hollyhocks have raised, orange dots under the leaves. I think the dots are eggs because the leaves get eaten. However, I can’t see any insects or worms on the plants. What should I use to kill the eggs or insects? I’ve used a sweet oil spray, but that didn’t work. (e-mail reference)

A: There are many insects that relish this plant. There also is a disease that takes it out as well, which is a rust fungus. I would suggest spraying with a fungicide to control the rust you are seeing. Find a product that contains chlorothalonil as the active ingredient. For the munching insects, use a product called Orthene. In spraying, be sure to cover both leaf surfaces completely. Try to get it done in the early part of the day to give the foliage a chance to dry.

Q: We have two Colorado blue spruce trees planted 20 feet apart in our backyard. We light the trees for Christmas every year. They are about 15 years old and are thin and in need of shape improvement. Can I trim them to thicken the branches and improve its shape? If I can trim the trees, how and when? (Lincoln, Neb.)

A: If you can, get someone who knows what he or she is doing and have that person do the trimming for you. Generally, cutting the branches back to an adjacent bud or cutting the emerging new growth to half its length will do the trick. Don't give into the temptation of using hedge shears because I promise you will overdo it! These are trees that need minimal pruning, so often people end up butchering them when they get a hedge shear or pruner in their hand. You are to be commended for having the foresight to plant these trees 20 feet apart. Too many folks make the mistake of thinking a spacing of 6 to 10 feet is more than enough.

Q: I purchased a ficus before Christmas for my new place. The home is a bright place with lots of windows, so the ficus has done really well. At first, it dropped a few leaves, but then started growing quickly. However, I noticed yesterday that the tree has a strange growth on one of its main branches. It is a round, bubble shape about 2 inches in diameter. It must have been there when I purchased it, but didn’t notice it until now. In fact, there is a small branch growing out of the bubble. The branch is more than a foot long. Is this a matter for concern? Do I need to do something or is this just an anomaly that is harmless to the tree? (e-mail reference)

A: This is a gall that is not harming the tree. If it bothers you, go ahead and prune it out. It could be caused by mites or very small insects that lay eggs in developing tissue. This activity causes the gall tissue to develop around the developing eggs. Eventually the critter exits and goes about a new life. You are probably right when you said the gall was there when you purchased the plant.

Q: We planted some irises in our yard that have been in my husband’s family for almost 75 years. Not knowing what colors were what because we dug them up in June, we planted half in a sunny flowerbed and the other half in a not so sunny flowerbed next to an American elm. The sunny flowerbed iris plants are growing like crazy five years later. In this area, we have brown/peach and bright yellow iris plants. The bright yellow plants have taken over and I have yet to see any of the brown/peach this year. I do, however, have quite a few stems that did not bloom this year, despite their continual growth. The not so sunny flowerbed has half deep purple and half yellow iris plants. For the first time, the purple plants did not come back and a lot of the leaves seem to be drooping and not standing straight. I’m concerned that they’re not getting enough sun. I’m also concerned that they’ll never come back. I should point out that when we dug these up five years ago, they never had been cut. The rhizomes, in some cases, were 12 to 18 inches long. I was so afraid of killing them that I never have cut them. I obviously want them to come back the way they were. Any suggestions about what to do? Can I move the ones near our American elm to the flowerbed without the yellow plants continuing to take over? Should I wait until they’re done blooming or should I move them to a separate, sunnier area and hope the purple come back? I always thought purple iris plants were dominant. (e-mail reference)

A: You are about at the point when you need to divide the rhizomes. Given enough light, the plants will flourish and have generous blooms for many years. In digging to divide, discard the oldest part of the rhizome. It is best to make it with a clean cut, although some gardeners will break the old rhizome off and plant the part containing the leaves. Dig up the plants after the flowers have finished blooming this summer. If you want to keep the colors straight, take a marker and put some code letter on the foliage to keep them separate after the flowers are gone. Be sure to dispose of the old rhizomes to keep iris borers from invading. I suggest a separate, sunny site for the plants that were under the elm.

Q: I read an article that said there is a peach tree for northern areas (zone 4). I was wondering if you knew anything about it. If so, where can I buy it? I live in zone 3, but this article says our winter temperatures are getting warmer and that some zone 4 plants possibly could grow here with winter protection. I also am planning to plant a couple of apple trees. What kind do you recommend? Thanks. (Mayville, N.D.)

A: Since you didn't tell me what the peach variety is that you read about, all I can guess is that you read an article about reliance peach. It is the most cold-hardy cultivar. It was developed in New Hampshire and is hardy in zones 4 through 8. If you want to believe the most recent update of the hardiness zones put out by the Arbor Day Foundation in 2006, most of the state is considered to be in zone 4. As to care, some people grow tpeaches and other marginally hardy plants in large tubs during the summer. Once the plants go dormant, they are moved into an unheated garage (the tub is on wheels). Others will wrap the branching system in any kind of insulation they can find. Some will bury the trees with soil and mulch in the fall before winter closes in. As for apples, the opportunity is more wide open. Take your pick of Hazen, Haralson, honeycrisp, honeygold, sweet sixteen, state fair or others.

Q: We are putting log siding on our home. We also are making changes to the foundation, so I had to remove most of the foundation plants. I would like to save some of the dwarf evergreens, but I don’t know much about them or what would be good for our area. I think they would look good with the log siding. The shrubs I was able to salvage were globe caragana, gold flame spirea and some dastardly, but beautiful sumac. Could you suggest a dwarf evergreen that would work? The foundation on our house is a little higher than normal. (e-mail reference)

A: A few that come to mind are dwarf mugo pine, dwarf Norway spruce, dwarf Colorado blue spruce and dwarf scotch pine. Enjoy!

Q: Through the years I have heard you recommend Fultz alkali grass for areas with soil problems. I see where the Agassiz nursery has nuttall alkali grass. Would nuttall be usable as a replacement for Fultz? (e-mail reference)

A: Yes it would. Nuttall is a newer and supposedly better cultivar.

Q: I purchased a new variety of amaryllis bulb this past year. When it bloomed, it was a bit taller than I expected and had planned for in the pot I selected. While I was away for a few days, the pot tipped over and the bloom stalk cracked. I cut the bloom stalk off and put it in a vase. I was surprised at what a great and long-lasting floral arrangement it produced. I also was surprised when it started to produce a seed pod. This is the first time I’ve had amaryllis seeds! The bloom stalk is completely withered and, of course, separated from the plant, but the seed pods are green. Should I wait to open them up and see if I have viable seeds to plant? If so, how long should I wait? I’m not sure if the seed pod will open on its own when it’s ready. (e-mail reference)

A: Let the pods dry naturally. After that, extract the seeds and plant, assuming something is in the pods.

Q: I would love to harvest some seeds and grow some Jack pine and blue spruce. Do I plant the seeds using peat and acidic soil? How long do I have to wait until the seeds are dry enough to plant? (e-mail reference)

A: I doubt you will have much luck with the Jack pine cones. Jack pine produces "seratonous" (resin-filled) cones that are very durable. The cones remain dormant until a fire occurs and melts the resin. Then the cones pop open and the seeds fall or blow out. Jack pines are among the first species to colonize a burned-out area previously inhabited by Jack pine. As for the spruce, the seed should be ready to plant when expelled from the cone.

Q: I planted two weeping willows at the back edge of my property (each end). They look great with leaves. However, the top 20 percent of each tree doesn’t look well. What should I do? (e-mail reference)

A: Prune the dead wood back to living wood. Some form of annual pruning will be necessary with this species of tree.

Q: I am from North Dakota, but now live in Wyoming. I want to plant snow-on-the- mountain on the back side of our horse barn that faces the driveway. I am a little bit worried about it because I have two small children. I have heard a few stories about it being corrosive and dangerous. I'm wondering if snow-on-the-mountain is that bad. My grandma used to have some by a fence in her yard when I was younger, but I don't remember ever getting into it. Thanks for any advice! (e-mail reference)

A: Grandma probably told you that playing in the plants could make you sick, so you very smartly listened and didn't go near it. Here is a quote from the poisonous plant text: "All parts of the plant are poisonous if ingested. Handling the plant may cause skin irritation or an allergic reaction." Hope you are enjoying life in Wyoming. It is the only state with a sparser population than ours!

Q: Just a quick question about fertilizing the lawn. I live in Moorhead and want to know when the best time is to apply fertilizer in the spring. (e-mail reference)

A: Anytime after you have mowed green grass a couple of times. That will result in maximum utilization and very little to no waste.

NDSU Agriculture Communication

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