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Published December 24, 2010, 12:00 AM

Hortiscope: Lack of dormancy period creates brown leaves

Q: I have a 15-year-old dogwood tree. The tree’s leaves turned brown instead of red this fall, and they have not fallen off the tree. All of the other trees lost their leaves weeks ago.

By: Don Kinzler, INFORUM

Q: I have a 15-year-old dogwood tree. The tree’s leaves turned brown instead of red this fall, and they have not fallen off the tree. All of the other trees lost their leaves weeks ago. We’ve had unusually high winds and an early freeze. I hope I didn’t damage the tree when I picked ripe berries from the low limbs earlier this year. I did this for two reasons. The berries make a mess on the ground, and raccoons have broken limbs in the past trying to get at the fruit. I have pruned the damaged limbs. Do you think the tree is dying? (e-mail reference)

A: Nothing you did should result in the leaves remaining on the tree and turning brown. This often is caused by the tree not entering into sufficient dormancy to form a complete abscission layer that causes the leaves to drop. Instead, the leaves die and turn brown. If you’ve had the tree for 15 years, it is unlikely that the tree is going to die. When spring weather arrives and the surge of new growth begins, the dead leaves very likely will drop.


Q: I bought two dogwood trees four years ago. When I bought them, the bracts were a dark crimson. Every spring since then, they bloom a light shade of pink. Is there anything I can do to change the bract color back to a dark crimson? (New Jersey)

A: This could be due to minerals in the soil, pH problems or nutrient levels being a little out of kilter. The New Jersey soil pH usually is the right type for good dogwood growing, but perhaps not in your particular location. I suggest contacting the Extension office where you live to see if someone can assist you. Go to http://njaes.rutgers.edu/county/ to find the Extension office closest to you.


Q: Thanks for your time this morning on the phone talking about the possibility of starting an apple orchard in the area. I’m in the early planning stage, but I really think it would be fun. Are there any fruit trees that would survive near a river bottom (Red River) where summer flooding would be more prevalent? How about berry bushes? What about fast-growing pulp trees? Are there other cash crops that could be planted in an area prone to flooding? (e-mail reference)

A: Look for riparian species such as elm and poplar. Elm wood is a good hardwood for making furniture, while poplar is used for pulping and rough, low-quality lumber purposes. Willows will tolerate all the flooding the Red River can throw at them, but I don’t know of an economic value to them other than in landscaping. Thanks for getting in touch with me and all the best.


Q: I’ve researched for the answer to my question but keep coming back to good North Dakota knowledge through the NDSU Extension Service office. Quite impressive with all the information that is available in the world! During the past three weeks, I have noticed what appears to be mold growing on the soil of my Christmas cactus. It looks like someone poured melted marshmallows on the soil. The white area is getting larger. The plant is flowering and doesn’t appear to be wilting or getting soft. I saw a similar question where you indicated a surface mold was a nonharmful growth. However, the person didn’t describe the mold. Please let me know if you think this is a problem. Your help is very much appreciated. (e-mail reference)

A: Thank you for all the kind words! When I stepped into this job 25 years ago, I never imagined that I’d be getting so many questions from all over the world. Anyway, you have nothing to be concerned about. This is a harmless saprophytic mold that is growing in the high organic matter content in your potting soil. It will complete its life cycle and disappear. If it bothers you to see it, scrape it off and dispose of it. We often see this in landscape settings where a lot of bark mulch is used around woody plants.


Q: We have 17 silver maple trees on a two-acre lot that are heavily infested with cottony maple scale. The last two years, we have been getting a sticky residue on our vehicles and buildings. We didn’t know what was causing it until this summer, when we noticed what looks like popcorn on the branches. Our ash and hackberry trees were not affected. We did some searching on the Internet and identified it as cottony maple scale. Is this something that nature will take care of on its own or does it need to be treated? What is the treatment? Besides the big mess it causes, we are concerned about it affecting the other trees. We live about 30 miles south of Watertown, S.D. (e-mail reference)

A: Any insect that builds up an unchecked population like you have will cause long-term harm to the host tree. You can control the problem with very little to no environmental impact by using a systemic insecticide containing imidacloprid. It is found in several retail products on the market. Bayer Advanced Tree and Shrub Insect Control is one of the products. To be effective, the label directions need to be followed precisely. Apply the insecticide in the early spring as the trees are coming out of dormancy.


Q: I combed through all your information about arborvitaes but was wondering if you could give me some advice specific to my plantings and climate. I planted five emerald green arborvitaes. One side gets the morning sun, and the other side is in the shade. I have experienced some browning and thinning out, but they were that way when I purchased them. They were planted properly using peat moss and good soil. The plants also are well-mulched. Our fall was so warm that green tips started sprouting and I could see new growth beneath the shedding leaves. This gave me much hope. Starting last week, the temperatures here have dipped into the 20s at night and 40s during the day. I have been watering them twice a week throughout the fall but wonder if I need to continue now that we’ve definitely had our first freezing weather. What is the best time of day to water? Thank you for your time and for considering yet another question about these wonderful trees. (Virginia Beach, Va.)

A: As long as the soil is not frozen, keeping the soil moist, but not soggy, will benefit the trees. Evaporation goes on through the foliage during the winter months. In the north, where the soil tends to freeze throughout the root system, very little to no water can be transported to the drying foliage, which results in what is termed winter burn. I can’t tell you how often to water your arborvitaes because it depends on soil type, mulch thickness and weather conditions. You will have to rely on what Americans have had to rely on for their own survival, which is common sense. I would imagine that Virginia Beach would have enough moisture available to see the plants through most of the winter months.


Q: We have had a ficus microcarpa plant for approximately three weeks. We have watered it a couple of times since we got it. However, the soil still is wet from the previous watering. It gets direct sunlight, but not all day. Several leaves turn brown and drop off every day. It does appear to be getting new growth, which is why we are confused. Is the plant dying? What should we be doing to it? Should we be spraying the leaves with water? (e-mail reference)

A: Any potting soil that remains wet after just a couple of waterings in three weeks means the plant is in the wrong potting soil or the pot has poor drainage. The unfortunate characteristic of this genus is that it usually goes into a leaf-dropping pout after being moved from the greenhouse or garden center to one’s home. However, these plants usually stabilize a month or more after the old leaves have abscised and are replaced with foliage that is tolerant of the new environmental conditions.


Q: The produce manager I spoke with at the grocery store said the yams in the store are definitely yams, not sweet potatoes. He said the yams come in many different sizes and grades, depending on the soil and climate where they are grown. He says sweet potatoes have less color and the flesh is more firm than yams. The sweet potato is the more nutritious of the two. They seem to me to come in various shapes and bake well. Can you confirm this information with a produce manager where you and your wife shop? (e-mail reference)

A: This discussion probably will go on forever but never be resolved. There is a website at www.loc.gov/rr/scitech/mysteries/sweetpotato.htmll that may or may not clear up this confusion. There is a more technical description of these two vegetables at www.ces.ncsu.edu/depts/hort/hil/hil-23-a.html. This website at http://wiki.answers.com/Q/What_is_the_difference_between_a_sweet_potato_and_a_yam also does a commendable job of explaining the differences. What’s my take on all of this? We are eating sweet potatoes 99.5 percent of the time in the U.S. I had this hammered into my thick skull while at the University of Georgia working on my master’s degree. Yes, they are called yams, but botanically they are sweet potatoes, so “a sweet potato by any other name still is a sweet potato.” I’ll check with the produce manager at our local grocery store the next time we’re there to see what name the store is using.


Q: We have a crab apple tree that is more than 20 years old. The fruit of this variety is miniature in size. The tree has very dense, thick foliage. We live in a humid and warm climate. During the last four years, we have noticed a reduction in the foliage and the flowering. The foliage this year is particularly sparse. There also are a lot of dead branches. We have, in the past, had to prune it back from the deck, but in the last few years, we have not had to do this. The base of the tree has a lot of debris around it, and the branches have what look like scars running along the length of the branch. These scars are a few inches to just less than a foot long. We have looked for borers but cannot see any holes. Hope you can help us with an idea of what has happened and what could be done to save the tree. (Auckland, New Zealand)

A: From what you have told me, this sounds like a possible root rot or crown canker problem that is causing this tree to decline so quickly. Generally, there is little or nothing that can be done to save the tree at this stage. From my perspective, you have a couple of options. You can accept the decline of the tree and have it removed. After that, you can plant another tree but be sure to use a different species. The other option is to collect some of the fruit, gently macerate it, collect the seeds, allow the seeds to dry and then plant the seeds in containers to try to produce another tree. Again, I advise against planting it in the same location because of disease organism carryover. There must be a university or an Extension-type service in your city that has some horticulturists on staff who can assist you with better suggestions and the possibility of saving your tree.


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 ronald.smith@ndsu.edu.

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