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Hortiscope

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

By Ron Smith, Horticulturist

NDSU Extension Service

Q: I have volunteered to help our church with yard maintenance. I need to trim back all the bushes, but my concern is the blue spruce tree. It is a very nice tree, but it is growing over the parking lot and very close to the church. Can I cut back the lower branches? I was thinking of doing the trimming 6 to 7 feet up the tree. (Milwaukee, Wis.)

A: If you prune the spruce, cut the branches back to the main trunk to save time, trouble and the frustration of having to go back and do it again in a few years. I promise it will not hurt the tree because I’ve done it many times.

Q: I just moved to a house in Indiana that has a dogwood tree. I have removed some small, dead twigs, but some leaves have turned a blotchy red and fall off when touched. Also, a couple of lower branches need to come off because they are growing over the sidewalk. I'm still not sure when to prune. Should I do it now, this fall or early next spring? (Indiana)

A: Horticulturists have followed an old adage for a long time that says there is a season for pruning, but it can be anytime when there is a reason. Some of the reasons include obstructing traffic or views, to remove dead or diseased branches, taking off spent flower heads or when safety is a concern. You can remove that branch now or early next spring.

Q: I purchased a new ficus benjamina last month. It was very lush and full. It lost many leaves after being moved, but I expected that to happen. Now that I can see into the tree, I can tell it was heavily pruned. There is a great deal of cut back to dead areas deep in the tree. There were many dead leaves deep in the branches that had been there for years. It's much tighter than any ficus I've seen. I did cut back lots of dead, woody material along with long, stringy root-looking vines in the center. I also have noticed three clumps of little, brown, dry grapes. I've noticed a few tiny flea-type bugs in the soil while picking up the dead leaves. Four weeks after I bought the tree, it still is losing leaves. I paid a fortune for this tree. It appeared healthy, but I don’t think it is. Can you please advise me? (e-mail reference)

A: Being as old as you describe, I don't think you have anything to worry about unless someone hacked this plant out of the ground and left most of the roots behind. The clumps you describe could be mummified fruits. The flea-type bugs probably are springtails. They annoy more than they damage. Repotting using a pasteurized soil usually will get rid of them. Keep in mind that plants are like cats. They thrive on routines that remain unchanged. You have moved this plant from what probably was an ideal location as far as light duration and intensity goes. The tree adapted to the watering regime and temperature fluctuations of the previous location. That said, very likely you have not duplicated what it had before, so it is "pouting" by dropping leaves. It will continue to do so until it reaches some kind of equilibrium with its new location and care routine. After that, it will begin generating new foliage. To make a long story short, be a little more patient. Don't try to push it with too much water or fertilizer while it is going through this adaptation.

Q: I have many gloxinias. I've raised them for years, but this year I lost my double pink. How do I make a new plant? (e-mail reference)

A: Basically, the method is the same as for other gesneriads (African violets). A fresh leaf will root in good light, high humidity and good soil. Use either perlite or vermiculite. You also can use a mixture of the two. Stick the leaves in a small pot and enclose everything in a plastic bag that zips shut. For faster results, put the bag under a fluorescent light. Gloxinia leaves root easily. The leaves produce a tuber and then a shoot that can be grown to flower. Gloxinias also root from tip cuttings and even from the spent flower stems that still have the calyx attached. Gloxinia are easy to grow from seed, which can be produced by self-pollinating a plant, but then the double flowering characteristic may very well be lost.

Q: I have an outdoor hibiscus that starts having buds around July. They do well and bloom, but then the buds and newly coming buds turn yellow and die. What could be causing this? I tried insecticidal soap last year, but it didn't seem to help. (e-mail reference)

A: This could be damage from thrips. These very small insects get under the flower bud scales and do devastating damage the same as you describe. Insecticidal soap would be rather ineffective against this pest. A systemic, such as Orthene, would be more effective because it is absorbed throughout the plant and will stop the insects when they begin to feed on the plant tissue. I encourage you to cut out the dead or damaged buds to keep this pest at bay.

Q: I purchase large planted baskets from our local Amish community every year. All my plants do very well with daily attention. Each year in July, my two favorite petunia baskets get sticky stems and I notice black dots on the lower half of the plant. Should I try a pesticide? What makes the stems and leaves sticky? (Indiana)

A: Stickiness without aphids is just the sweet goodness of the plants being exuded to the surface. Didn't you ever as a kid harvest petunia flowers and suck on them or lick the stems? I'm probably dating myself or being cataloged as a "flower sucking or licking nut," but we had to find some way to entertain ourselves in those days. Examine the black dots with a magnifying glass to determine what they are. The dots could be insect droppings from previous occupants, insect eggs or just dirt specks. Don't be too quick to use pesticides unless absolutely needed.

Q: I have four small spruce trees. Last year, worms started eating the needles. I used several sprays from the store, but to no avail. Then I started killing them with my fingers. There was no end to them. This year, the needles have not returned, but there is new growth on them. If the worms return, what should I use to get rid of them? (Park Rapids, Minn.)

A: Sevin is what you should use because it will kill them on the spot! Those worms are sawfly larvae that have the appetite of a high school football team.

Q: We have eight blue spruce trees. Two of them are dying, but I'm trying to save them. We live in an area that has been getting a lot of high wind. One tree wasn't affected because we had it tied well, but it is dying anyway. We had a landscaper put down mulch in the fall, but I feel it was too much. I pulled back the mulch and got rid of some of it. I also fertilized the tree. The other tree was affected by the wind, so it is bent over. Should we take it out and replant it? How much mulch and how close to the base should it be? Also, how do I know if the tree is dead? Our soil is like clay, so I used composted manure and peat moss. Thanks for your help because I'm new to gardening. (e-mail reference)

A: Blue spruce is tolerant of winds without any input from humans, so I wonder where it is you have them planted and how they were planted. Many people, even professionals, make mistakes. One is planting too deeply. The top of the crown where the trunk transitions into the roots should be no deeper than at ground level. Don’t apply fertilizer at the time of planting. Some people overwater the planting. Keep it moist, but not soggy. As you assumed, some people use too much mulch around the tree. The mulch should be organic material, not rock. The mulch should not be up against the trunk of the tree. Keep the mulch 3-plus inches away from the trunk. An evergreen can have green needles but be dead. Think of “live" Christmas trees as an example.

Q: I transplanted a 2-year-old red Japanese maple tree about three weeks ago. I watered it every day for about 15 minutes, but the leaves all withered. What do you think? (Greenwich, Conn.)

A: That is typical transplant shock, which is about the same as open-heart surgery on humans. If the patient (tree) survives, it will releaf a little this year. Otherwise, it is finished. Trees, such as the Japanese maple, should be planted in the early spring before the buds break out. Stop watering it every day. The roots need air along with water.

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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