Hortiscope

Ron Smith, Extension Horticulturist
North Dakota State University

Q: I was asked to look at a mountain ash that looks like it was freeze dried on the spot. It's a tree that's about 16 years old. It is growing between two large green ash trees. There was another mountain ash planted the same time which is beautiful tree. This tree is stunted. The symptoms are that all the leaves are hanging on it but are brown and dead with a few tips that still have some green leaves. It also set the orange berries. The sprouts on the main tree trunk and root sprouts are all dead. The home owner says no spraying has occurred and broad leaved weeds are present in the lawn. There is a lawn sprinkler system in place so I don't think it is due to drought.

Does fireblight hit mountain ash? Would it start from the inside and move out since there are the ends of branches that still have green leaves? (E-mail reference, Ellendale, N.D.)

A: It sounds like a very clear case of fireblight, especially if the client has an irrigation system working around the tree. The system keeps the tree in a succulent state, which then makes it vulnerable to the fireblight bacterium. All they can do now is cut it down and get it out of there.

Q: I have planted gladiolus bulbs in my garden for years and I always dig them up in the fall. I always had a beautiful variety of colors until this year, when they were mostly yellow and white. How is this possible? Also, after my delphiniums finished blooming I cut them back. Now we have had so much rain that they have grown about 18 inches and are forming buds. If I trim them back again this fall will they flower next year? (Garrison, N.D.)

A: Your first question stumps me -- I have no idea why they would change colors! Mutations are possible, but not on the wholesale basis you describe. Yes, the Delphiniums will flower again next year for you. They often get two blooming periods in during a growing season if the summer is long enough.

Q: We have an apple tree that has a lot of fruit every year, but about half way through the season the apples turn soft, rotten and brown. Do you have any idea what could cause this problem? (E-mail reference, Horace, N.D.)

A: Sorry, but I don't know what would cause what you describe. Any ideas from readers?

Q: We dug out bearded iris bulbs today. I would like to know if there is anything special we need to do to them before we replant them. We had been told that you need to soak them in bleach but that seems kind of harsh. (E-mail reference, Indiana)

A: Soaking in a bleach solution is standard if disease was noted in the digging. Of course, the diseased material was discarded, so the soaking is to nuke out any remaining spores that may be existing on the rhizomes. If everything seemed clean, then simply replant at your earliest convenience. I've done that for years and have never had any problems!

Q: We planted a common wood rose about four years ago. It is now at least 6 feet tall and seems to have done well, until this summer. Quite a few canes, mostly lower ones, seemed to die off. Checking closer, I found that the canes had in fact broken off. And, at the point of the break, the stem was enlarged. If the cane were 3/8 inch in diameter, for example, there would be a barrel-shaped enlargement that was perhaps 1/2 inch in diameter and nearly an inch long. That's where the break occurred, often low on the plant. I haven't been able to determine what caused the swelling and subsequent breakage. We had a similar situation earlier this summer with our downy hawthornes, which are now about 8 feet tall. Through the early summer I would find that the end of branches (perhaps the last 6 to 8 inches) had died. Again, there was a break of the stem, although I didn't notice any enlargement, growth, or reason for the breakage. Is there something we should be doing for either of these problems yet this fall or next spring? (E-mail reference, Mandan, N.D.)

A: Both the rose bush and the hawthorn are in the rose family and are subject to gall problems. One in particular, the crown gall, sounds like it is doing the work on your rose bush. It is more of a parasite than a pathogen and can weaken the canes it attacks, causing the breaking off that you describe. Even though it isn't the crown of the hawthorn that is being attacked, I believe it is the same organism, as it is known to attack the branches of apple, pear, cherry, and hickory, to name just a few. There is a possibility that a stem girdler (an insect) could have caused the breakage on your hawthorn since you didn't notice any swelling. I suspect the gall fungus, though, since it was in the area where rose bush was attacked. To be sure, you might want to check the branches where the breakage occurred to see if there is a possibility of borer activity at that point. They often lay eggs on branch tips and the larvae, about the size of mechanical pencil lead, would bore under the bark, girdling the stem causing dieback and often death to the tip. Where it is for sure the gall, the only control for homeowners is sanitation. That means cutting out all infected plant parts and disposing of them. None of the over the counter fungicides are labeled for control.

Q: We live in South Carolina and have a hibiscus plant that is doing very well. They truly do love the sunshine here. However, my wife insists that we bring it inside for the winter, while I believe it will do fine planted in the ground. Our winters here have never fallen below 25 degrees since we've lived here. I am willing to keep them watered as necessary and would love the ability to have them re-bloom in the spring and summer. So tell me, what is the best solution here? (E-mail reference, Lexington, S.C.)

A: Oh you lucky guys in the banana belt! Of course you can grow the hibiscus outdoors in your part of the country! If I were you, I would play it safe and make sure the root system was mulched going into your joke of a winter down there, just to be on the safe side, in case a sudden freeze shows up. That way you won't lose any points with your wife! Really, there should be no problem. Plant it in a sunny spot and enjoy.

Q: I'm interested in planting Harry Lauder's Walking Stick for its beauty but I also would like to eat the filberts/hazelnuts. Only the Sunset Western Gardening Book mentions that the nuts from this shrub-tree are "good" in flavor. Do you know if the walking stick actually produces edible nuts, and are they reasonably good eating? (E-mail reference, Cedar City, Utah)

A: The Harry Lauder's Walkingstick (Corylus avellana 'Contorta') is grown for the unique, twisted shape that the branches and leaves form in the landscape, not for the edible nuts, which occur only rarely in landscape settings. I would suggest that if you want the nuts for eating that you grow the American or European species and not this expensive cultivar. Besides, if it did produce nuts, every squirrel within miles would be fighting each other to harvest them before you could get to them. I assume you saw this at a local nursery or garden center and know whether or not it is hardy to your particular area of Utah.

Q: I am having a problem with my 20-year-old Christmas cactus. The leaves are falling off and there are brown, dry spots on the leaves. Is this condition fixable? What do I do? It bloomed beautifully all this time. Watertown, S.D.)

A: The spots on your cactus plant indicate a condition known as edema, due to water-logging. I suggest repotting using a peat-based mix made more porous by adding coarse sand or peat to every three parts of the standard mix. Keep it in the east window. Make sure the pot is free-draining.

Q: My yard is very compacted and extremely rough (my lawnmower takes quite a beating); it's also high in clay content. I picked up literature at the local Extension Office regarding lawn renovation. I have a fairly good catch of grass and reseeding does not appear to be needed - just better fertilizer management and an aeration program. That will help the grass but not the roughness. I am thinking about wetting the soil and then running a roller over the lawn. That will no doubt increase compaction. Will aeration ultimately mitigate this increased compaction? Other options I've thought about are tilling the lawn and starting over (uff da), or spreading black dirt over the existing lawn, but I fear that without incorporating the new dirt into the existing hard lawn I will have a poor interface. (E-mail reference, Bismarck, N.D.)

A: Rolling a lawn with a ballast roller is a good practice to correct the problems you mentioned. The increase in compaction is not bad, and is usually not a detriment to the turf. Yes, later core aeration will correct any excess compaction that may have taken place. You can also run a power rake over the lawn before rolling to help level things out somewhat, but do not till everything up. This will only pull up a ton of weed seed that will welcome the opportunity to germinate for you. Then you'll really have a headache!

Q: I had a call from a patron this morning regarding their pear tree. She said it is about 16-17 years old and to her knowledge has never had a blossom on it, but they discovered three pears and tasted one. She said it was wonderful! It was shaped more like an apple. Her question: Is there anything they can do to encourage it to bloom and bear fruit? (E-mail reference, Tower City, N.D.)

A: It is not unusual for pears to have an apple shape, after all, they are in the same family!

What it needs is another pear to act as a pollinator. The Ussurian pear would be a good one and should be available at many garden centers.

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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