NEWS for North Dakotans
Agriculture Communication, North Dakota State University
7 Morrill Hall, Fargo, ND 58105-5665
September 28, 2000
Ron Smith, Extension Horticulturist
North Dakota State University
Q: Can you tell me why my red maple tree that I planted in the beginning of May is not doing very well? It was healthy when I planted it, but since then every new leaf that comes out turns black around the edges and then gets dry. It has had enough water and I have been spraying it with Triple-Action (insecticide-miticide-fungicide) since the middle of June. Nothing seems to help. Thank you. (Bemidji, Minn.)
A: The plant appears to be suffering from leaf scorch- - which is a poor description of what is actually going on. In your particular case, this is an abiotic (non-pathogenic) cause. Simply put, the roots lack the capability to supply sufficient water for that lost at critical times. Newly transplanted trees (within the last year) frequently manifest this problem. This ties in directly with the condition the root system is in. Perhaps too much was removed during the nursery digging; the salts (from fertilizer or otherwise) could be too high, the soil could be anaerobic from a rising water table, too much watering, or simply from compaction. Other problems could be a root disease, plastic mulch over the roots, too much mulch ("mulch volcanos"!) or an early infestation of feeding aphids. I suggest trying to give the tree as much reasonable good care as possible. Don’t over-water, do not fertilize, but attempt to keep the tree from undergoing any excessive stress. You might want to get a soil test taken and request to have the potassium (K) level checked. If it is low, then an application of that element as potassium sulfate may help. Other pointers might include vertical mulching- - vertically augur the soil out at several places around the tree, going down about 12 inches and backfilling with pea gravel- - and finally, spraying the tree with an anti-desiccant like Wilt-Pruf as the new foliage emerges next spring.
Q: I have two gardening questions for you. The first one concerns the enclosed leaves from our raspberry bushes. The leaves are turning yellow and the plants seem to be drying up. The berries are small, seedy and fall apart when picked. Can you tell me why this is happening and what we should do? Next, we also raise several roses, hybrid teas and florabundas, and have been able to keep the black spot in check. This year with all the rain it has been impossible with several of them losing almost all the leaves. We spray with Ortho Rose Pride Finginex and lime sulfur spray but can’t seem to get ahead of it. Is there anything that would work better? (Enderlin, N.D.)
A: With the raspberries I suspect tarnished plant bug damage on the fruit. They are small, destructive, sap-sucking insects that feed destructively through every instar of their life cycle.
They overwinter as adults in leaf/weed trash and crop residue. They feed on the flowers and developing fruit, causing deformed, "nubbins" which you describe. Practice good sanitation and early spring spraying with Sevin to control. Once roses get black spot, that is usually it for the season. Just keep spraying and collecting the infected leaves. Next spring begin a protective spray schedule as soon as the new leaves unfold.
Q: Can you tell me what is wrong with the enclosed sample from my tree? For the last 15 years it has been green and never dropped branches until this spring. I water it once a week and it was transplanted about 6 months ago, which is when I think the problems started. Can you tell me what the problem is and what to do to solve it? (Wilton, N.D.)
A: Norfolk Island pines (Araucaria heterophylla) are beautiful but finicky plants! Change something and they defoliate! This can be anything from a change in the watering regime, air temperature, humidity, drafts, and potting soil. If you can, try misting the foliage with distilled water. Make sure the plant pot does not stand in water after watering, but keep the soil evenly moist. Try to reflect on what has changed -- even slightly -- since you repotted. That would be your first clue as to what could be causing this.
Q: What can we use to get rid of white clover? I used Curtail, but the grass goes too. I didn’t know that it would run all over the yard, but it is starting to take over. Would 2-4D work? Also, why won’t grass grow where a tree stump was? (Campbell, M.N.)
A: If you can find a lawn care operator that uses Confront for broadleaf weed control, that will do it better than anything else. If you cannot find anyone who uses Confront, try a couple of applications of Trimec. You are correct. White Dutch clover will move into a low fertility lawn and eventually take over unless checked. The grass is not growing where the tree stump was is likely due to alleopathic compounds remaining in the soil. Excavate some of the soil and replace. That should take care of the problem.
Q: I have a creeper that is impossible! With these wet years the conditions are encouraging to the plant. They tell me it is "creeping Charlie." I want to get rid of it, but I don’t want to kill the grass. What can I do? (Cresbard, S.D.)
A: In some cases you might be better off allowing the creeping Charlie to remain, especially in the shade and north side locations. If you are determined to get rid of this without killing the grass, I suggest using Trimec. It will take two or three applications or more over the next year, but it will do it, selectively. There are precautions with this product which need to be observed to keep from damaging surrounding plants. Otherwise, you can use Roundup which will kill everything off -- grass and weeds -- giving you the option to replant with grass seed.
Q: I have a Redmond linden, planted in 1983, which has become a very nice tree. Someone told me that they are shaped like a deciduous fir, tapering to the top, and I find this is true. My question is how close to the ground to let it grow? I have removed some of the down-growing bottom branches so that it clears the ground and the trunk is probably clear up to about 4 feet. Is there a guide to growing these trees? (Ellendale, N.D.)
A: What you are doing with your Redmond linden is correct. If you wanted to limb it up farther, that would be correct also. In essence, whatever you are happy with! It is your tree. The small leaf-like appendages are bracts that drop after the flowers. They break down easily and blow away quickly. This temporary mess is a small price to pay for such a beautiful tree.
Q: Are all the fruits on flowering crabapple trees edible? We have one that produces dark pink blossoms in the spring and this year it is loaded with small dark red to purple apples. Are these edible? (E-mail reference)
A: All fruits on crabapples are edible - some more than others - depending on the size and how juicy they are. Just be sure they have not been sprayed with a pesticide.
Q: How do I go about encouraging ground wasps to leave? (E-mail reference, LaMoure, N.D.)
A: You are dealing with an animal that resists encouragement to move out. They will repay most amateurish efforts with a volley of stings and bites. So, unless you know what you are doing, you are better off letting a pest control service remove them. Otherwise, here are some suggestions:
1. Trapping - there is what as known as a Seabright trap that is for temporary use, and an IPC trap that is for longer term use. Wasps have been known to escape from each, so handling these traps filled with wasps should be done with caution.
2. Nest destruction or removal. Caution is emphasized here, as a careless action can result in many unpleasant stings. This requires that the nest be located and approached after sundown when the wasps are all back inside. Protective clothing is strongly suggested. Often, chemicals are used to kill the inhabitants before destruction or removal takes place. A pyrethrin/rotenone aerosol is used, and is sold under the commercial name of "Wasp-Stopper." Sevin can also be used for the same purpose.
3. Vacuuming. A professional company locates the nest and literally vacuums them out of the nest into a tank. Often, they are then frozen and sold to venom collection companies.
Q: I have a spider plant that has grown a string of babies. I'd like to plant them, but have no idea how to do it. I see what looks like sprouts at the top of the babies. Do I need to let those root in water? Should I plant them directly in soil? If so, do I put the end in the soil or the other end as it naturally grows on the stem? (E-mail reference)
A: Spider plants produce what I call "spideretes" or asexually produced plantlets that can be directly planted into containers of their own. Many folks will take them as they are attached to the mother plant and pin them into some soil in an adjacent pot. After about 2 weeks they cut them away from the mother plant. Others will simply cut the "mature" ones off and pot them up, misting them until they appear established. Enjoy!
Q: When you prune a mock orange, do you take each branch right down to the ground or do you remove a section that has had the flowers on previously? The shrub is about 7 feet high and very cluttered where the old flower heads were. It looks very messy and unattractive. (E-mail reference, Saskatoon, Sask.)
A: It sounds like your mock orange is in need a rejuvenation pruning. To do that, and not lose the vigor of the plant, I suggest that you wait until next spring and prune before it re-leafs. Get long-handled loppers and reach into the base of the plant and cut everything out, as close to the ground as possible. The resulting vigorous growth can then be shaped to your desire. That first year you'll sacrifice the flowers, but that is a small price to pay to get a new and vigorous shrub.
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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.
Source: Ron Smith, (701) 231-8161, ronsmith@ndsuext.nodak.edu
Editor: Gary Moran, (701) 231-7865