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

By Ron Smith, Horticulturist

NDSU Extension Service

Q: I have a small growth on my young hansa rose. I have a much older one that has galls, but these bumps are different. They are quite small and located on the branches. The galls are in groups. I pulled one off, which left behind a powdery substance on the branch. The growth was hollow, but, when I pinched it between my fingers, it oozed. Is it a bug of some sort? (e-mail reference)

A: There are insect galls and bacterial galls on roses. Since the gall started to ooze when you broke it open, my guess is that this is an insect gall. Bacterial infections typically ooze without pinching. As a sweeping generalization, galls typically do not cause problems other than to worry the owner needlessly. If the rose is performing to your expectations, I wouldn't worry about these galls because they naturally come and go each year.

Q: I am wondering if you think it is a good idea to plant oats with grass seed. Someone recommended this to me as a way to get a lush lawn and protect the grass as it grows during the summer. If so, how much oats would you mix in with the grass seed? (e-mail reference)

A: Mixing oats with grass seed, especially when hydroseeding, is at least as old as I am, which is pretty old! I don't know that there has ever been a formula for how much oat seed goes with grass seed. We just threw a few handfuls into the hydromulcher to get the effect we wanted and get paid faster. If you want a hard figure as a guideline, I would suggest about 1/2 pound per 1,000 square feet of area being seeded.

Q: We purchased a willow that has grown into a lovely tree. We live in the desert. I faithfully feed and water the tree, but last year I noticed it was turning yellow and loosing leaves. I can't find any bugs, sawdust or sap, but I have found some holes on the trunk and branches. Do you have any idea what this is? Can I help this tree? I have read your column and am afraid you are going to tell me the problem is borers. (Deming, N.M.)

A: This sounds like poplar borer damage. See if you can locate an insecticide that is sold under the Bayer brand name as "Bayer Advanced Insect Control for Trees and Shrubs." It may be too late, but willows are pretty tough trees and have been known to bounce back almost from the dead.

Q: I typically start my own bedding plants each spring using a small greenhouse that I purchased. The problem is that my seedlings develop a very poor stem and root system and become leggy before they fill out. What am I doing wrong? (Jamestown, N.D.)

A: Spindly, weak growth is the result of keeping the air temperature too high and not having enough light. Supplemental lighting is needed to start most seedlings, even in greenhouses.

Q: I have a question about a lawn that won't grow. It's on the north side of my house and gets very little sun. I've tried reseeding. I'm wondering if landscaping the area with stone mulch would be a good idea (less work, more economical) rather than keep trying to grow grass. If so, what kind of stone mulch would you recommend? I don't want it to look like a playground with pea rock. (e-mail reference)

A: I strongly advise you not to use stone mulch. The stones migrate to other areas of the yard and create heat islands. Stone mulch leaves no surface for recreation or relaxation. It also collects dirt where weeds will grow. You have not been using the right grass seed. Look for fine leaf or creeping red fescues because they are the most shade-tolerant grasses. You couldn't have more shade than I have on the northern exposure of my own backyard. The grass is shaded by the house, a large Ponderosa pine and an Amur maple tree. I am successfully growing an attractive turf cover of creeping red fescue in that area.

Q: After scouring the Web looking for help with my Canadian red cherries, I found your site and was impressed. I live in a suburb of Denver that has clay soil. My neighbor has a red cherry pruned as a tree. It is full, robust and about 20 feet tall. I bought two red cherry trees two years ago. I had the nursery plant them in our backyard. The holes were dug to their specifications and I had them backfill with clay-buster soil. At the time, the leaves were somewhat small and sparse, but I was told that within the next two seasons, the trees would fill out. It's two years later, but the trees still look sickly. The leaves are small and many are sort of folded. About 10 percent of the smaller branches are bare. Of the branches that have leaves, some seem to be burdened by their own weight. The branches are almost doubling over because the leaves are concentrated on the ends. I haven't been running the sprinklers or directly watering this year because of the abundance of snow we had. I have not observed any insect infestation or signs of the dreaded black knot fungus. The nursery has been no help. Should I prune the leafless branches? Do Canadian red cherries thrive with more or less water? Is there a fertilizer or tree food that may help? I welcome any other suggestions you may have. (e-mail reference)

A: First of all, I think the nursery should get a good dressing down for not standing behind its plantings and for delivering subpar trees. It sounds like the root system was deficient or damaged when the trees were planted, which would explain the crown thinning and the poor leafing out. I would encourage you to go back to the nursery to work out some kind of compromise on tree replacement. You should pick out the trees to be planted. Look for nice, full crowns, with normal-sized leaves. If they are decent businesspeople, they should meet you at least halfway on this. If they refuse to work something out with you, the Better Business Bureau should hear about their less than ethical standards. Next time, go elsewhere for the trees you want.

Q: I have a fairly large area of creeping phlox on a side hill in the front lawn. It has bloomed well the last few years. Some of the plants are getting too long and there was some winter kill in spots. Should phlox be trimmed? If so, how often, when and how much? (e-mail reference)

A: Trim it back after it has finished flowering and give it a shot of Miracle-Gro or a similar product. It can be done annually, but it is not needed. I would suggest doing it when the plants start to get that ragged look that you describe.

Q: We have a problem with our chokecherry trees. We had black knot disease, so we sprayed the trees with a fungicide after trimming the infected branches. They were OK for a year, but now the disease is back. We tried trimming again, but the trees are in a shelterbelt and we can't keep up with the fast-spreading disease. We can't remember the name of the fungicide. Could you please help us with the name of the fungicide or any other ideas you may have to help stop this ugly fungus from spreading? (e-mail reference)

A: It is an ongoing task to control black knot once the plant has become infected. In early spring, the tree should be sprayed with lime sulfur prior to bud break and after the visible knots have been removed. A fungicide known as Cavalier (thiophanate-methyl is the active ingredient) is then sprayed at bud break, in full bloom and about three weeks after that. I really don't have a vendetta for the hapless chokecherry because I think they are beautiful trees and their fruit makes good jelly and wine. I had one in my backyard years ago, but when black knot disease and suckering started occupying too much of my time, out it came! If Mother Nature gives us a break with some drier summers, but not too dry, it will help slow the spread of this disease.

Q: What causes a rosebush to loose its leaves at the bottom of the bush? Is there anything that I can do to get them to grow back? (e-mail reference)

A: This is likely black spot fungus. Once the leaves have dropped, they are gone for the season. Do some pre-emptive spraying with a systemic fungicide next spring. There are many systemic fungicides on the market to select from.

Q: I want to transplant some Amur maple shrubs. How many shoots should I transplant together and what should the spacing be? I want them to be shrubs, not trees. Thanks for your help. (e-mail reference)

A: Generally, the clumps are in three or five. If you want them to be shrubs, pack them together as one. Root grafting eventually will take place, if it hasn't already done so, which will not hurt anything. Then space these clumps as far apart as you want. You're taking a chance of losing these plants by doing the transplanting now. Survival rates would be much higher in early spring or fall when they don't have foliage.

Q: I purchased a pipestone plum tree, but I don't know much about plum trees other than I wanted one. Will this tree bear fruit? I don't know if I have any cross pollinators in my area. I do know that there are apple trees and other various fruit trees nearby, but I am not sure how cross pollination works. (Calgary, Alberta)

A: Chances are there are pollinators in your area. Generally, anything within a quarter mile will be effective as a pollinator. Plums will produce without cross pollination, but will be more productive if one is nearby.

Q: I have a shooting star hydrangea that is in the process of budding. I just noticed fresh sawdust on the leaves and found a hole in one of the canes. Is there anything I can do to stop and/or prevent this from happening? (southern Delaware)

A: This is a cane borer. Cut the affected area well back from where you see the activity taking place and spray on an insecticide sold on the market as "Bayer's Advanced Tree and Shrub Insecticide." Be sure to follow the label directions.

Q: What is the best time of the year to split and replant peonies? (e-mail reference)

A: A good rule of thumb to follow is to divide and transplant spring-flowering perennials in the fall and fall-flowering perennials in the spring. Midsummer flowering perennials can be divided and transplanted in the spring or fall. Peonies fall right into the fall transplanting schedule.

Q: We planted a Colorado blue spruce a couple of years ago. This is its second season of new growth. This year, the upper part of the tree is producing an incredible amount of cones. Nearly everywhere there should be a new branch forming, there is a cone instead. There are so many cones that the branches are hanging down because of the weight. The tree looks healthy otherwise. Is it safe to pluck the cones off or what else can we do? We are afraid the branches might break. (e-mail reference)

A: Picking the cones off may cause more damage than just allowing them to drop on their own. Generally, heavy cone production is a sign of tree stress, but usually it occurs on much older trees. You might assess your tree for planting depth, water needs or any other possible environmental stressors that may be causing heavy cone production.

Q: I have several types of peonies planted together. In other gardens in my area, I see peonies with heavy blooms that seem to stand tall without any artificial support. Mine seem so long-stemmed that they droop over. Am I doing something wrong? They have been in place approximately seven years. Thanks so much! (e-mail reference)

A: You're not doing a thing wrong. It is common for peonies to need support because of their heavy blooms. Stop the fretting. Get some hoops so you can enjoy the beautiful flowers! There is no shame in providing support for any flowers. The difference could be in the soil microclimate.

Q: I purchased a hardy northern azalea two years ago. The first year, it set buds in the fall, but a rabbit ate them during the winter. It again set buds last fall after new growth. It is now happily flowering from the bottom up. Is this normal? I have a lot of buds on the branches from top to bottom. All the buds on the bottom of the plant are blooming. The top buds of the plant are not opening, but are getting new leaves alongside the buds. Do you know why these did not open yet? (e-mail reference)

A: This sounds like an example of snow cover verses no snow cover. The plant is flowering from the base because the snow protected the buds from lethal temperature changes. The flower buds at the top of the plant did not have continuous snow cover and therefore reached a lethal temperature. Flower buds have a lower tolerance for extreme low temperatures than foliar buds, so you have the leafing out that's taking place.

Q: Four years ago, we transplanted spruce trees from a farm. They where planted very close together on the farm. We planted them with more spacing, but are noticing their growth is heavier on the top and have not thickened up. The only advice we were given about fertilizing was to use additional lawn fertilizer around the trees when fertilizing the lawn. These trees now are top heavy and I feel they will break off. Is there anything we can do to save these trees? I have considered cutting the tops off and letting new growth begin. (e-mail reference)

A: That would be an acceptable alternative, if you don't mind trees that are not the typical symmetrical form.


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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