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Horticscope

Ron Smith answers reader's questions about the world of plants and gardening.

By Ronald C. Smith, Horticulturist

NDSU Extension Service

Q: We live in Oklahoma and have arborvitaes in our backyard in full sun. We have the plants around our pool for privacy. The arborvitaes did great the first two years. Late last summer, when it got extremely hot in August, they started turning a golden yellow on one side, which quickly turned to brown. We read that the problem could be spider mites, so we sprayed the trees for mites. The trees did not come back and turned almost completely brown. They have lost their foliage during the winter and now most of them only have small patches of green here and there. A few plants are green on one side. We have fertilized them in hopes of helping them come back. Is there any hope of them reviving or should we give up and replace them? Any advice would be appreciated. (e-mail reference)

A: I think the problem is more than spider mites. Evergreens around a paved pool area and under high temperature conditions are going to be impacted by chlorine vapors volatilizing from the pool. I would suggest removing the plants and doing a replanting because they never will recover to your satisfaction. In the future, when extremely hot weather is forecast, soak some open-weave burlap with water and loosely wrap it around the plants. This should protect the plants from excessive heat and chlorine damage. Be sure the roots have adequate moisture while they are under this kind of stress.

Q: I have a cottonwood tree near the Rio Grand River in Albuquerque, N.M. All of its leaves turned brown and dropped very early last fall. The bark appeared to dry up and die in spots. It is budding this spring, but I am noticing a number of places where a sticky, black substance is oozing from the bark. I cannot find any sign of insect activity. Also, it has quite a few little, orange, resin-looking spots all over the white trunk. The spots almost look like insect eggs, but are not. All of my other trees are similar in age and growth, but have none of these issues. (e-mail reference)

A: The black oozing you describe sounds like a bacterial infection. I strongly suggest that you contact an International Society of Arboriculture certified arborist to inspect the tree. To locate one in your area, go to http://www.treesaregood.com/. Click on "Find a Tree Care Service" and follow the links to your community. Be sure to check for credentials and ask for references before allowing any major work to be done.

Q: I looked at some of the answers you gave to others on your Web site and saw that you mentioned problems with spaded trees. We planted a spaded green mountain sugar maple five years ago. The tree has not grown leaves on the first foot or two of the crown during the last few years. Also, it has grown very little since it was planted. However, other than that, it looks fine. I've tried giving it fertilizer spikes, but nothing happened. Is there anything I can do to help this tree? The tree is very important to us because my wife's family had it planted for us in memory of our son. (e-mail reference)

A: Unfortunately, this sounds like the tree did not have sufficient root pruning during its life prior to being spaded into your new site. However, it could be that an undersized spade was used in moving the tree, so not enough "feeder roots" that are capable of taking up sufficient water and nutrients were included. You may be able to have it come out of this funk with professional help. I suggest that you contact an International Society of Arboriculture certified arborist in your community to find out if something can be done to help the tree recover the vigor it should be showing. Go to http://www.treesaregood.com/ to find an arborist. Explain everything to that person as you did to me. Perhaps a treatment of deep-root airing, using what is known as an air spade, might do the job. An air spade is a tool utilized in arboriculture to clear away soil from around the base of a tree. This tool utilizes a high-pressure stream of air to move soil away from the base of a tree without causing any damage to delicate tissue. With the soil removed, the arborist or a landscaper then can bring in some "designer soil" that is composed of one-third good, loamy topsoil, one-third sand and one-third composted organic matter. In most cases, this work would involve soil removal out to the drip line of the tree. There has been research supporting this technique in pulling trees out of decline from construction compaction, but not specifically from tree spading. There is no guarantee this will work, but it is the best bet you have going for you to preserve this tree. While the arborist is there, he or she also should prune out any dead limbs the tree has because they never will recover.

Q: I am writing from the east coast of Australia. It is a reasonably warm, sunny spot most times of the year. We are putting in a fiberglass pool about 3 meters away from a crepe myrtle. Someone has told us that this tree has an immense root system that may damage our pool. I really like the tree and am hoping it can stay where it is. (e-mail reference)

A: Crepe myrtle has a fairly extensive root system, but it only would be a threat to your pool if it leaked. If you want to feel secure, you could have a root barrier installed for little extra cost when you install the pool. I would suggest this be done, even though there is nothing really to worry about under usual conditions.

Q: I am in search of a flowering hanging basket that our local greenhouse used to carry. I think it’s in the begonia family. Someone told me its common name is shippy's garland. It has large, dramatic foliage and long canes with medium-sized red flowers. Any ideas? (Perrysburg, Ohio)

A: Here is the information I was able to find on the begonia you wrote about. Good luck! Trailing scandent begonias grow up or down. They grow vinelike and usually with many branches. They lend themselves superbly to hanging baskets or trained to grow up posts, trellises and totem poles. Most are packed with small leaves and usually bloom profusely. The flowering season varies from plant to plant. These begonias are good subjects to grow hanging from tree limbs, under lath covers, or greenhouse roofs or in front of large windows. Some trailing scandent begonias you may find are B. convulvulacea, B. Ellen Dee, B. Elsie M. Frey, B. fagifolia, B. glabra, B. mannii, B. Marjorie Daw, B. polygonoides, B. procumbens, B. shippy's garland and B. splotches. These begonias need plenty of light, but no intense midday sun. Good light will help produce a full plant with lots of blooms. If leaf stems elongate and the space between stem joints gets larger, you know the plant needs more light. If the foliage pales, you are providing excessive light. The usual comfortable temperature range for people of 58 to 72 degrees also is right for trailing scandent begonias. The humidity requirement is average for begonias at 40 percent to 60 percent. Potting is more crucial than with some other begonias because the long, pendulous stems are sometimes fragile. If you use plastic containers, be careful not to overwater. Some feel clay, wood or moss-lined wire baskets are better. A squat or somewhat shallow container is best because the begonias are shallow-rooted. Don't overpot. When repotting, put the plant in a new container only a size larger. Too much extra space can produce weak plants and the extra space retains so much water that the plants drown. Staking isn't necessary, but pruning and pinching can make the difference between a so-so plant and a great one. Prune out old stems that have long, bare sections. Pinch stems often to encourage branching and to obtain stems of varying lengths to get a full, shapely plant. Water when the planter mix feels dry to the touch. If the weather is warm or the plant seems to dry out faster than other begonias because it is in a hanging basket, water it a bit more frequently. Spraying leaves with water in the morning increases humidity and washes off dust. A complete fertilizer used throughout the active growing season should be supplemented just before and during the blooming season with a high-phosphorus food. Trailing scandent begonias easily can be propagated using stem cuttings, especially tip cuttings you create when you pinch and prune. This free-flowering species listed in the Rosecroft Begonia Gardens catalog as B. alba scandens in the 1920s probably is B. glabra.

Q: We have a large silver maple that is more than 40 years old, about 80 feet tall and has a trunk diameter of at least 6 feet. We will be cutting the tree down to make room for an addition to our house. Is the wood good for lumber to build furniture? Does it make sense to contact a lumberyard to see if it will buy the wood? (e-mail reference)

A: From what little I know about wood used for furniture making, I would say the silver maple is not a good candidate because it has soft wood. Norway and sugar maples, which are considered hardwood trees, most often are used for furniture work. It wouldn't hurt to contact the lumberyard to see if it would be interested in purchasing the wood. It may turn you down or accept the wood and turn it into crate or pallet wood.

Q: Several years ago we planted three Manchurian ash trees on our boulevard. Last year we noticed the trunks of the trees had large cracks and a large number of ants at the base of the trees. Basically, the trees are not looking very healthy. Any ideas on what is going on and if the ants are contributing to the health of the trees? The neighbor's Manchuraian ash trees also have bark that is peeling off. (Fargo, N.D.)

A: This is probably "sunscald," which is a misnomer. On thin-barked trees, such as young ash, apple and many others, the sun hits the south or west side of the bark on a cold winter day. This causes the internal temperature of the tree to rise above the ambient air level. When the sun sets or moves behind a bank of clouds, the tissue on that side freezes, which causes the fissuring or cracking that you describe. To prevent this from happening, it is recommended that the tree bark be wrapped prior to the arrival of winter weather and the wrapping removed when spring arrives for good. This needs to be done every year until the branch spread protects the tree on that side and/or the bark develops a corky quality to it that can resist this problem. The ants are not contributing to the health or decline of the tree.

Q: I have a 30- to 40-foot spruce tree in the courtyard just outside my condo. The condo association wants to cut it down because there is a membrane system about 30 inches below the surface and the tree is growing over the parking lot. It is a beautiful and healthy tree. Can spruce trees go down that far? I thought spruce trees were shallow-rooted. If it does have to be cut down, what would you recommend in its place? (e-mail reference)

A: A depth of 30 inches is not beyond the reach of a spruce tree's roots. As to what to plant in place of the spruce, I would prefer you contact someone locally who is knowledgeable about the horticultural selections you could make. I have no idea where you live and cannot make blind recommendations for a replacement. Someone at a local garden center should be able to assist you in making a new selection.

Q: I just came across your Web site and found it extremely helpful. I planted 30 emerald green arborvitaes along my back property line in New Jersey about three years ago. Unfortunately, four of them died last year. What concerned me was the progression in which they died. One started to become brown and wilted and became progressively worse. Then the same thing happened to the one next to it and so on down the line. I thought it might be a disease, lack of water or insects, but I'm still not sure. I employed several tree experts to offer advice. All had different opinions. Thankfully, the rest have been OK, but I am starting to notice that some of the other trees are getting a little thin looking. I do not want the same thing to happen because I have put a considerable amount of time and resources into these trees and am hoping they will grow into a nice privacy barrier. Any idea what killed the four trees last year? What kind of fertilizer do you recommend using in New Jersey? Is fertilizing once in the spring all I need for the entire year or should I do more? On a separate note, I have six other emerald green arborvitaes that I planted two years, but now I want to transplant them. Is this advisable? If so, how should I do it? I am building an addition and probably will lose them anyway during construction. (e-mail reference)

A: Thanks for the nice comments about the Web site! As to the problems you describe with your arborvitaes, you have good reason to be concerned. I only can make some vague or wild guesses about what might have killed the four trees. The problem could be root rot, spider mites, borers, any number of fungal diseases or poor drainage. What you need to do is contact the Rutgers University Plant Pathology Department to see if it has a diagnostic clinic that can assist you. I would start by contacting your New Jersey Extension Service county agent to find out if someone from the office is a horticulturist or urban forester and can come out to collect soil and root samples. If necessary, that person also may need to collect foliar samples. The agent then would send the sample to the university’s diagnostic clinic. The agent also can make better recommendations for fertilizer needs than I can from here in North Dakota! Miracle-Gro is a good default fertilizer. An annual application, just as new growth is beginning to show, is more than enough. Fertilizer spikes are a waste of time and money. You have nothing to lose in transplanting the smaller arborvitae. Dig a rootball, roll some burlap under and around the ball and then carefully transport it to the new planting site. Plant them at the same depth they were at the original site. Do this at your earliest convenience because spring comes early in your part of the country!

Q: I recently purchased a ficus tree that was in a discount area at my local hardware store. It has been losing a lot of leaves, but new ones are slowly growing. Some of the leaves that are falling off have black areas on them. I do not know if it is a fungus or if this is normal. I thought it was getting too much sunlight, but I do not know how that is possible because it is kept inside and only gets indirect sunlight. (e-mail reference)

A: Based on what you have told me, the ficus is not getting too much sunlight. I doubt that you have anything to worry about. What you probably are witnessing is the elimination of the old foliage that started declining in the hardware store. The plant’s new location is more conducive to the gradual emergence of new growth. Enjoy watching your ficus recover from being in a poor environment to one that is more suited to what it needs!

Q: My grandmother had two beautiful crown of thorn plants that she had trained or bent to make them grow in a circle. We are now raising plants that came from her original plants. As she is no longer living, I was wondering if you had any suggestions as to how to get my plants to also grow in a circle. Any help would be much appreciated. Thank you. (e-mail reference)

A: You can use wire coat hangers, PVC-coated low-voltage wire or a wooden frame. Like any plant that is intended for training, you need to work with the new growth as it emerges by tying it into place.

Q: I'm writing you from the banana belt of south Fargo. This winter I noticed a white, cottony infestation on the hawthorn tree in our front yard. Can you tell what this might be and if you can, give us some advice on how to deal with the problem? We dearly love this tree and don't want to lose it. (e-mail reference)

A: Those are the remains of the cottony cushion scale that made a big impact on woody plants last year. The problem hit silver maples, lindens, hackberries, honey locusts and even hawthorns. Cottony cushion scale can cause branches to die back and cause crown thinning, if the scale population grows unchecked without any predator interplay. A lack of predators apparently has been a problem in our region during the past few years. There is a systemic insecticide marketed by Bayer that is available on the local market. Be sure to follow label directions exactly! The white popcorn growths you have been observing this winter are the dead adults. What will happen now is that the eggs that were laid last year will hatch and the crawlers will migrate to a suitable place on the branches. The crawlers will insert their styletts to begin feeding and in the process, cover themselves with a protective, white, waxy covering.

Q: I live in Texas and got the seeds from my red lion amaryllis to grow in a Burpee seed kit that I keep near a window. However, I don't know what to do next. I'm clueless, but so far successful. Do I plant them outdoors? Do I use a pot or do I leave them in the seed kit until the bulbs form? I can experiment with some indoors and outdoors, but I would feel guilty if any die. They are very cute. Also, when will the bulb form? I planted the seeds indoors in January, if that helps. (e-mail reference)

A: Now that they are up and looking cute, gently move them to pots. The plants should stay in the pots through the summer months. As the foliage continues to grow, the bulbs eventually will form. By this time next year, you should have a nice, small bulb from each seedling you now have. Give yourself about three years to get the plants to produce a flower. For more details on amaryllis plants, go to http://www.ag.ndsu.edu/pubs/plantsci/landscap/h811.pdf or http://www.ext.nodak.edu/extnews/hortiscope/flowers/amaryllis.htm. Enjoy!


NDSU Agriculture Communication

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