October 11, 2001

Hortiscope

Ronald C. Smith, Horticulturist
NDSU Extension Service

Q: I have several questions about things going on in my yard in north central South Dakota. We had a green ash (Marshall) and cottonwood (Northland) planted six years ago and now about 20 feet tall, which were thriving until this spring, when neither leafed out. I suspect sprayer damage, since others in the yard are fine. Now there is regrowth coming up from the bottom of both. Should we tear the trees out and replant, or prune the regrowth to let just one shoot grow, or if we let them all grow, what will it eventually look like? We have an Autumn Blaze maple, also about six years old, which is 18-20 feet tall. I have no experience with maples and am wondering what the normal leaf color should be during the spring and summer. Ours is pale to bright yellow-green. It seems healthy, but I'm wondering if it is lacking in nutrients. Is columnar buckthorn susceptible to fireblight? Ours has stems on which the leaves have all turned a red-brown, seemingly all at once. The leaves are crispy, and are all still on the branch. This appears randomly throughout one bush, and has killed back entire sections of another. If not fireblight, then what else would be causing this, and how should we treat it? My 20-year-old Hopa crab has, for the last two or three years, leafed out, bloomed and looked healthy until mid-June when the leaves begin to look diseased. They begin to yellow and have spots on them, and by now are dropping in large numbers. It doesn't seem to affect its growth the following spring, but am wondering if this is something we should be treating or ignoring. (Eureka, S.D.)

A: All good questions! I would suggest removal of the ash and cottonwood. Sometimes sprouts will make a decent tree, but 99 percent of the time not. I'm afraid you would only be frustrated.

The maple sounds like a trace element problem. Try applying chelated iron to see if that helps. Often the high pH of the soil messes things up for leaf color development to be proper.

Buckthorn is not susceptible to fireblight, and I don't know what would cause similar symptoms unless it is a bad case of rust. Do you have any oat fields in the region? Oat is an alternate host.

Apple scab is common on Hopa crabs. Clean up fallen leaves this autumn; spray with lime sulfur next spring when dormant; spray with Bordeaux mixture at leaf out, and again 7-10 days later there after; Or, just live with it as you have.

Q: It seems like the older my lawn becomes the more weeds it contains. In recent years two weeds have become quite common and they are quite difficult to reduce. The first is crabgrass for which I use a fertilizer that contains a preemergent chemical, but this system does not seem to be very effective. Perhaps I should use a straight preemergent chemical on the crabgrass without the fertilizer. What formulation do you suggest? Is there another species of crabgrass-like plant that I might have? Secondly, I noticed some violets in the yard about 10 years ago and thought I could live with them. After several years I sprayed them, but had zero effect. I have used Trimec in various parts of the year and with a surfactant and they curl up some but then recover and grow with abandon. I talked to the lawn professionals in Jamestown and they said they can not get rid of them with their chemicals. I read that Turflon is recommended, but I have not found this chemical in stores. The local Cenex said they can order it for me, but the smallest amount I can buy will cost over $100. I am ready to try Turflon as the violets have taken over my lawn. However, I would like to know if it is effective. (Jamestown, N.D.)

A: Violets are tough to control. Ask your lawn care professionals to get Confront. This is the most effective broadleaf weed control product I have seen on the market for turfgrass use. Don't go out and spend $100 for Turflon when the lawn care operator can get the Confront product. This fall would be an ideal time for application.

Q: We have a long row of basswood trees planted in the grove on our farm. My husband and I are having a disagreement over how they should be pruned. I want to prune them so that they are shaped like trees, taking off the bottom branches each year. My husband thinks that they should be more like big bushes and wants to leave all of the growth on them so they are bushy from the ground up. Are either of these two ideas right or is there a different way that they should be taken care of to get a properly shaped tree? (E-mail reference)

A: You are both right. It all depends on what you want from your trees, a hedge barrier or a stately row of trees that are limbed up to view beneath. The former is more a European choice, while the latter is more American. It might all boil down to simply whether or not there is anything worth while looking at beyond the trees. So, take your pick!

Q: I received a small, white blooming hydrangea bush around Easter 2000. I planted it soon after. This past summer of 2001 it did not bloom. Perhaps it was getting too much afternoon sun as the leaves wilted often. I recently moved it to a less sunny spot, gave it good soil, and mulched. It appears to be doing better now. Can I expect blooms next summer? Would a fall application of fertilizer help? (E-mail reference, southeastern Pennsylvania)

A: Try to find out what kind of hydrangea it was. It will probably not flower for you next summer, because it may be the type that has flower buds that are not hardy enough to survive Pennsylvania winters, and all you will get is the foliage. That is often the case with florist hydrangeas.

Q: Our trumpet vine is destroying our house foundations and neighbor's driveway. We cut down the vine, but its runners are popping up all over the place and pushing through the asphalt driveway. This is an emergency! Does anybody know a way to destroy the darned thing? We have been putting stump remover (potassium nitrate) into the stump and have been pulling out the runner sprouts coming up to surface, but no use. The vine will soon cost us extensive foundations repairs, a new driveway for the neighbor or maybe even several more asphalt toppings. (E-mail reference)

A: Wow! Sorry to hear that. You are doing the right thing with the stump killer; try "painting" the emerging sucker growth with Roundup. It will take persistence, but you should win!

Q: What are the chances that my 'Donald Wyman' crab trees are grafted/not grafted? I lost quite a few this past winter, and want to know if I can choose a nice sucker from the many that are sprouting and cut out the little dead tree. I don't want any crab but Donald Wyman. I do not see signs of a graft, but I am not all that proficient, I'm afraid. (E-mail reference)

A: Not very likely, unless someone before you happened to root a cutting and plant it successfully at that location. Just about every named crabapple that I know of is a clone of the parent, which means that it was vegetatively propagated (grafted, budded, or by cuttings) from the parent tree. It is unusual to hear of a survival problem with this named cultivar, an introduction from the Arnold Arboretum which is in the Boston area. There is also a slight chance that the graft was buried at planting, and some of the sprouts that are arising from the base could be above the graft union and would therefore still be the 'Donald Wyman' crab.

Do you have a gardening or houseplant question? Write to Hortiscope, Box 5051, NDSU Extension Service, Fargo, ND 58105 or e-mail to Ron Smith at ronsmith@ndsuext.nodak.edu. Note to e-mail correspondents: please identify your location (city and state) for most accurate recommendations.

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Source: Ron Smith, (701) 231-8161, ronsmith@ndsuext.nodak.edu
Editor: Gary Moran, (701) 231-7865, gmoran@ndsuext.nodak.edu