May 23, 2002

Hortiscope

Ronald C. Smith, Horticulturist
NDSU Extension Service

Q: I have a wiegela bush that needs pruning. How much can I take off ? Does it bloom on old or new growth ? Does it bloom heavier one year, not so heavy the next? Like lilacs? (Jamestown, N.D.)

A: The wiegela does some of both, old and new growth. It may have an alternate blooming cycle, but I would bet that it has more to do with the fact that the flower buds may be borderline hardy and what happens is the buds formed on the previous season's growth get nipped in some winters. Remove about one-third of the oldest canes right back to the ground.

Q: Last summer, during the hot, humid weather we had, a lot of my annuals (such as impatiens, dahlias, Amaranthus and delphiniums) seemed to turn brown, dried up and eventually died off. They were all planted on the east side. I have grown them there for many years and this is the first time such a thing ever happened. The ones that were more shaded from a neighbor's tree were not affected as severely. It almost looked like spider mites, but I could find no evidence of them. Could it have been rust? I have never seen rust on my plants before, so I would not know if it is that for sure. I use these same plants along the whole east side of my house, as they always did so well. (E-mail reference)

A: First of all, the plants you listed are not all annuals; secondly, it is impossible to tell you what could have killed them off with the information available to me. It is very unlikely that there was a pathogenic organism that attacked all of those plants at the same time. I would suspect herbicide drift or a soil sterilant causing this mischief with your plants. Try a soil test before planting this year to see if the nutrient balance is ok or not. If it turns out to be all right, then I suspect something of the latter to be the problem.

Q: What causes tulips to not flower? A friend of mine separated hers and gave me around 20 bulbs last year. I planted them in late fall and now only have healthy looking single leaves. They were not planted in one spot, which makes it even more strange to me. And my friend has the same problem with those she replanted. (Detroit Lakes, Minn.)

A: There are a couple of possibilities. They could have been planted too deep; damage was done during the digging and transplanting or the bulbs were undersized when transplanted. More likely than not they will flower next year if you can leave the foliage on until it dies down by the end of June.

Q: Why don't Amur chokecherry trees, Prunus maackii, seem to get black knot? Are there other Prunus species that don't succumb to black knot? (Moorhead, Minn.)

A: A lot of it has to do with population density and the fact that the pathogen (Apiospornia morbosa) may be very host-specific. Or it may be that those species of Prunus are simply more resistant to the disease.

Q: My husband has allergies. He was told that he should avoid planting our new yard into Bermuda, fescue, Johnson, June, orchard, perennial rye, redtop, salt grass, sweet vernal, and timothy. What's left that is hardy enough? (Buchanan, N.D.)

A: Unless the person advising your husband meant Junegrass to be the same as Kentucky bluegrass, he can certainly plant that species. I suggest 'Park', 'South Dakota Certified', or 'Kenblue' as possible cultivar selections. He could also plant fairway crested wheatgrass.

Q: I have a burr oak about 10-12 years old (approx.10 feet high). A few weeks ago I noticed the main trunk bark was a rusty color and appeared to be peeling off. Today I noticed the main trunk has split open; there is a crack longitudinal with the trunk is about 1/8 inch wide several feet long. The tree appears to be getting ready to bud leaves. What is this problem and what can I do to keep it alive and healthy? (Bismarck, N.D.)

A: Sounds like a frost crack has developed and is likely occurring on either the south or west side of the tree where wide swings in tissue temperature can be expected. Unfortunately, there is nothing that can be done, except to hope that callus tissue will seal over the fissure that has developed. To keep this from recurring, wrap the trunk of the tree in sisal-kraft paper, burlap, or simply whitewash the tree trunk this fall, before the cold weather arrives, and remove it before Mother's Day the following spring. While it is unusual for an oak to suffer this kind of winter damage, this can occur to any tree species, especially if any damage was done to the root or branching system some time ago at the time of planting. This could have taken place from pruning or damaged plant parts.

Q: We are looking for a good book on the care of fruit trees, particularly apples and plums. We are very interested in pruning information. We do not need a book with a lot of pretty photographs but a more "professional" quality book that has diagrams. Any recommendations? (Bismarck, N.D.)

A: I suggest a visit to a major book store like Barnes & Noble to visit their horticulture section. I find the publications put out by the Reader's Digest organization to be quite informative and authoritative. Seek those out to see if they can be a help to you.

Q: A gardener asked me for the recipe for manure tea. Do you have a recipe? (Cando, N.D.)

A: Manure or compost "tea" is simply the liquid that is collected from compost or well-weathered manure piles. A cheese-cloth or untreated burlap is used to filter the solid stuff out. Soak this "bag" of compost or manure in a watering can or barrel for a couple of days, then dilute it to a weak-tea color. Reuse a couple more times, then use the solid material as a mulch or to condition the garden soil.

Q: My back yard faces a large field. All last summer we constantly battled a daily tick problem with our two outside dogs. This spring we are once again starting to remove them on a daily basis. We want to treat our lawn area with something that would deter the pests and help with the problem but need something recommended that would not harm our dogs in any way. Can you recommend what to use? (Minot, N.D.)

A: Ticks in a suburban setting are a little unusual. I assume you are keeping your lawn mowed.

What you need to do is contact a professional exterminator to come out and treat your yard. Some lawn care companies have competent personnel on board that can carry out such missions. This is something I would not recommend that you do yourself. A professional with the right equipment and formulation will do a much better job.

Q: Just reading some information on the Internet on Trimec. I have ground ivy and it is in my perennials. Perennials include hostas, day lily, tulips, iris, mums, etc. Can I apply Trimec on my perennials and not kill them? (Fergus Falls, Minn.)

A: Trimec will very effectively take out your perennials in addition to the ground ivy. You can use Roundup with caution, covering the perennials as you spray around them.

Q: When is a good time to move an apple tree? It is 4 feet tall and starting to bud. (Linton, N.D.)

A: I would say it is a little too late. Wait until the tree goes dormant this fall and replant at that time.

Q: I was wondering if 30-degree temperatures would hurt petunias, marigolds and impatiens that were planted outside now. (E-mail reference)

A: It depends. If they are close to the house, no; if they were hardened off, no; if the 30-degree temp comes for only an hour or so before sunrise, no; if a frost accompanies the temperature, most likely. The impatiens would be the first to go, followed by the marigolds, followed by the petunias. I suggest throwing a cover over them for the night.

Q: My Haroldson apple trees are finally starting to leaf out. Is now a bad time to trim the branches that are almost hanging on the ground? (Valley City, N.D.)

A: Yes, it is a bad time, unless you want to take a chance with disease. It should have been a month or more ago.

Q: I live in south Moorhead with an empty dirt field across the street. I have a problem for the past few weeks with ladybugs in my house along the south window. I have a south front door and picture window and there are ladybugs along the floor and window sill every day. I spray and vacuum and they keep coming. Can you give me any advice? (Moorhead, Minn.)

A: Just put up with it or fight it the best way you can. The mild winter has led to an abundance of these helpers, many of which will starve to death due to a lack of sufficient food.

Q: About seven years ago we planted two trees that were labeled "Cottonless Cottonwood." After seven years of no cotton, this year both have begun producing cotton. Why, now, have they started doing this? Is it normal? Will they now do this every year? Did we buy trees that were mislabeled? (E-mail reference)

A: Briefly; they are now mature enough to produce the "cotton"; yes and yes. Sorry.

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