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Hortiscope

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

By Ron Smith, Horticulturist

NDSU Extension Service

Q: We have had our chokecherry tree for three years. It has been growing and doing great. This year, the branches are bare for the most part. However, new leaves are starting to appear from the trunk. There also are leaves on some of the braches. The tree does seem to be healthy. Should I cut the branches that are not producing leaves? (e-mail reference)

A: If the branches are dead, then remove them. I would be suspicious that all is well with this tree despite the emergence of new growth. Monitor it closely for bark beetle, borer damage or stem cankers.

Q: I just planted nine Colorado spruce trees. A couple of them have split branches near the bottom. However, each side of the split still has green needles. Is there any way to save a branch that is split? (e-mail reference)

A: Not really. You are better off cutting off those branches back to the trunk. If you don’t, these branches will be a source of disease and insect problems for you. As the trees mature, you will never miss them!

Q: I have about 30 Colorado blue spruce trees planted in a field. I have had a serious issue with bagworms the past few years. Initially, I was hand picking the worms and disposing of them. When the number of pests grew, I tried spraying with Sevin once and Talstar another time. It killed the pests, but immediately took the blue out of the trees I hit. It was as if I was painting with my pesticide wand. Is there a pesticide for bagworms that isn't harmful to the color of the tree? Someone once told me to spray when the sun is low or in the evening. If this year is as bad as the past two, I will have too many worms to pick by hand. (New Jersey)

A: Get some imidacloprid (Merit) to use on the trees. It is a systemic and does not depend on making contact with the pests. Instead, it kills them as they feed. This material can be found in at least two commercially available products. They are Ortho MAX Tree and Shrub Insect Control and Bayer Advanced Tree and Shrub Insect Control. These products shouldn't change the color of your spruce. However, I think your trees will "reblue" with subsequent new growth.

Q: I have been told that if you plant multiple colors of coneflower (yellow, orange, red, white and purple) that they will revert to purple if a purple one is planted in the same area. Is this true? I have had all of these colors in my garden for the past two years, but they are holding true to their original color. (e-mail reference)

A: What you were told is not true. Your multiple-colored plants are hybrids that don't cross with the common types.

Q: I have a 4-year-old Christmas cactus that is drooping terribly. I've repotted it in cactus soil, but it looks so sick. What do you think could be the problem? (e-mail reference)

A: Let's start out by asking about the roots when you did the repotting. If they were white and firm to the touch and had extensive growth, then this is a simple case of transplant shock. The plant should recover if you don't overdo the watering. If the roots were dark and tended to flake off when handled and did not have extensive growth, then this could be a case of root rot developing. If you cannot recall what the roots looked like, then slip the plant out of the pot and examine it. Leave the plant alone if it has white roots. If it has some dark roots, prune those out completely. Christmas cactus is an easily propagated plant, so I would encourage you to take some cuttings as a hedge against this one expiring.

Q: I bought three pink myrtles. Each has one trunk. Do I just let the suckers that come up from the ground grow to get the four trunks that I am after or is there some other way to end up with four trunks? (e-mail reference)

A: If you want four trunks, purchase another one and cram plant them together in the same hole. Their roots will graft together and produce an attractive clump for you. If you depend on sucker growth, they either will not sucker or what will come up as suckers will have a different flower color than the scion wood. However, I’m assuming these are grafted plants.

Q: What is a good shade tree to plant near a driveway that will not drop sap on cars? We bought an accolade elm and are wondering if it would be OK to plant it near the driveway. (e-mail reference)

A: This tree and most others will be OK as long as you keep the insect population under control. Aphids love this species. The two have evolved together through eons, so if the aphid population should build up, the sap will flow through their feeding bodies and get everything sticky beneath it. However, aphids and other sap-sucking insects, such as scale, mealybugs, leafhoppers and plant bugs, can be controlled effectively with systemic insecticides. It would be unrealistic to think that any tree would remain free of insects. Some sticky sap flow from insects is to be expected. To what degree depends on the pest population density and to what extent predatory insects can keep them under control.

Q: I have three blue spruce trees that have started leaning over. I had an excavator dig a trench for me, so now the trees lean in the direction of the trench. The trees have been in the ground for four to five years. Should I wet them heavily and try to stake them back on the opposite side until they are straight or would this damage the roots? (e-mail reference)

A: If done properly and for a length of time, there would be no damage to the roots. It is kind of like straightening teeth. The dentist puts a gentle, but continuously increasing pressure on the teeth to get them straightened. After a few years, the objective is achieved and the patient has a beautiful smile! I assume this is something that occurred just recently and not a year or two ago. Use a soil anchor and make sure the strap bracing around the trees is flexible and broad enough so that breakage will not occur in high winds or the strap will not girdle the tree. Get the straps as tight as you can using hand power. Tighten the straps every few days until the trees are back to vertical. Keep the bracing in place for the rest of the growing season to allow the roots to get reoriented. If the work took place a year or more ago, then a different approach should be considered. Dig a trench outside the spread of the branches and have the trees straightened in the above manner in one operation. This would require greater care and effort. It also would require a pickup truck or loader of some kind to apply the pressure. Once the trees are at vertical, stake them and refill the trenches. To save some work and time, but spend a little more money, you could hire a contractor with a tree spade to lift and reset the trees in the same hole. Staking would be needed here as well for the remainder of the growing season.

Q: I have a hydrangea that I have had for 10-plus years. For the last two years, it only blooms on the backside of the bush. There were no blooms in the middle or front. Any ideas on why this is happening and what we can do to prevent this in the future? (e-mail reference)

A: There is a whole family of hydrangea species. Some bloom on last year's wood, while others bloom on the current growth. The endless summer cultivar blooms on any old or new living wood. You must have a species of hydrangea that blooms on new or old wood. If you have been pruning the front of your shrubs back and they are producing bloomless new growth, then they are a cultivar that blooms on the previous season's growth, which you or someone has removed by pruning or caused by some type of physical damage.

Q: One of my spirals seems to be turning brown. It might be from a lack of sunlight because it is the only one facing north, so it doesn’t get much light. It also is located near a downspout, so it may get more water than the others. Is there anything you can recommend that is all natural? I have not fertilized these trees. I read something about needing more nitrogen. Also, can you comment on the use of coffee grounds in my garden? Can there be too much? (Long Island, N.Y.)

A: The tree is not in the right location because it gets too much shade and water. To confirm the problem, get in touch with a local nursery or landscape company. As for the coffee grounds, there is nothing to worry about! I’ve been doing if for years and the plants, earthworms and robins are thankful for it. In fact, if you want more, the local Starbucks coffee shop may be giving away their used grounds for that purpose. They do it in this part of the country.

Q: I repotted my jade plant using Miracle-Gro potting soil. It seems that the stems are too heavy, so they have fallen over and pulled some roots out slightly. Did I not pot it deep enough? Will it stand up again? Your advice will be greatly appreciated. (e-mail reference)

A: Reset the plant a little deeper and prune off no more than 25 percent of the top of the plant to stabilize it in the container. It shouldn't hurt the plant. Doing this is better for the plant than having it list to one side and pulling out some of the roots.

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.


NDSU Agriculture Communication

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