September 22, 2005

Hortiscope

Ronald C. Smith, Horticulturist
NDSU Extension Service

Q: I have a client who has two old (likely hopa) crabapple trees. The trees looked normal to me, but the client mentioned that they are not putting out pink spring flowers like they used to. Could it be that the trees are simply going into decline? The leaves look clean at this time of year. (e-mail reference)

A: Ask the client when the trees were last pruned. That is often the problem. Intelligent pruning during a two- to three-year period will bring them back to their full show.

Q: Are there any chokecherries I should be concerned about? A friend gave me some to try for winemaking. He said they are Canadian chokecherries. They contained no pits, were dark red and about the size of a pea. It would be great if you could help me out with this so I don’t get extremely sick or get some poisoning (other than from the alcohol). The plant was purchased in the Fargo area. (e-mail reference)

A: If it doesn’t contain a pit, it isn’t a chokecherry. Even though this is coming from a friend, I would be leery about consumption, unless you witness your friend eating them or drinking the wine. As humans, we vary in our tolerance to different things that we consume, so be careful.

Q: We had two raspberry plants in our small backyard. We decided to remove them and replant with strawberries. Now we have multiple raspberry runners coming up all over the place. We are using Roundup to control the spread. Is there any way to kill all the raspberries or do we have to write off this growing season and use a soil sterilizer? (e-mail reference)

A: You have been hit with “raspberry surprise”! These plants actually are weeds, but we have fallen in love with their fruit, so control them like weeds. The persistent application of Roundup to the foliage and digging out of any little sprouts eventually will do the job! Hang in there.

Q: We transplanted three flowering crab trees at a new house three years ago. They were 15 years old when we had them moved with a tree spade. They were moved in November. The next year they looked excellent. The following year about a third of the branches lost their leaves in the spring. In the fall, the bark on those branches looked like they were suffering from sun scorch or fire blister. Those branches were cut off last fall. This year I have noticed woodpeckers around the trees. Is there any hope for these trees? Can I cut the tops off the trees, leaving only the trunk, so new branches will sprout? (e-mail reference)

A: Cutting the tops off the trees is about the worst thing you can do to a tree and have it resemble anything that would be considered a real tree species. You are better off removing the trees, if you are not satisfied with the way they are growing. I assure you that moving crabapple trees that old left many roots behind. These trees put out extensive flare and feeder roots that make it difficult for them to survive transplanting. I suggest removing the trees and replanting. They grow quickly and you’ll be happier in the end.

Q: We live near Brookings, S.D. We bought the land in 2000 and have been planting new shelterbelts since then. We have done this before using trees from the Conservation Service and usually are good at it! We’re having trouble growing amur maples in a couple of areas. We have discovered that area used to be old cattle or hog lots. The evergreens are doing well, as are the red twig dogwoods and the chokecherries. Is there too much of a particular nutrient in this ground for amur maples to thrive? If so, is there anything we can do or should we give up and replace them with another shrub? What would grow well in this soil? I read your column every week and have learned so much. Thank you! (Arlington, S.D.)

A: It is unusual that amur maples will not grow where other plants will. I don’t know what to say, except to go with the ones that will make it. Generally, amur maples will grow almost anywhere, in some cases to the point of almost being a pest! Thanks for being a faithful reader of the column!

Q: We read your column in the newspaper every week. We are trying to plant some fruit trees. We had a pear tree that did not survive the early frost. We want to replace it, but one of the problems we have is the trees blossom too early and then frost hits them. Do you have a recommendation for a pear tree that does not blossom early and is suitable for North Dakota? How about a peach tree? (Jamestown, N.D.)

A: Thank you for being faithful readers, it is appreciated! I also have had bad luck with pear trees. Either the blossoms are killed off or fireblight hits, so my recommendations will be tongue in cheek at best. Look for these cultivars at a local garden center: summer crisp, parker, luscious or gourmet. I tried summer crisp, but it finally succumbed to fireblight. However, other folks have told me that they are successful at growing and enjoying fruit from this cultivar.

Q: I have an oak tree (not sure what kind) in my front yard. At the base of the tree, shoots are coming up. It looks like it might be new shoots from acorns dropped or else it is coming from the base of the tree under the ground. Is it safe to cut these back? If so, is there a better time of year to do that? (e-mail reference)

A: The shoots probably are suckers. Cut them off anytime they show up to keep the tree growing vigorously.

Q: I have a vegetable garden that is swarming with roly-poly (or pill) bugs. What little I’ve read about them says they are beneficial to a garden because they clean up rotting vegetation, but there are so many of them that I can’t imagine they won’t damage my crop. When I pull a radish, I see dozens of them surrounding the root. Can I use Sevin to kill them? What do you recommend? (Wall, S.D.)

A: Sevin will take care of them and not be detrimental to your vegetable garden.

Q: We have a burr oak tree. Last year some small “balls” appeared on it and the new leaves started to curl. We sprayed with Diazinon, which seemed to help, but the balls started again this year. Some are the size of chokecherries and some about an inch in diameter. The inside seems to be fibrous and very lightweight. What are they and is my tree doomed? (Clearbrook, Minn.)

A: There is nothing to worry about! Oaks are prone to getting galls growing on their leaves, petioles and branches. They do not hurt the tree, but do provide some ornamentation for you to enjoy. Some people make a hobby of collecting oak and other gall formations.

Q: I enjoy your column so much. We planted a dark-leaved maple tree last year. It grew fine and had leaves. It is now early June and it still doesn’t have leaves. When we scrape it with a fingernail, it is green. Will it eventually get leaves and grow? The other question is about a blue hydrangea plant my husband gave me for Mother’s Day. I would like to keep it growing. I plan to put it outside when it is finished flowering. Do I leave it in the pot or plant it in the ground? Would I have to bring it in for the winter or could I put mulch around it? What do I use to keep it a blue color? (Watertown, S.D.)

A: If it doesn’t leaf out in a couple more weeks, I’d say forget it. As for the hydrangea, plant it in the soil and fertilize with aluminum sulfate to maintain the blue color. Mulch it well this fall just as the ground freezes. Cut it back heavily early next spring, before new growth begins.

Q: I have transported some iris bulbs from my mother-in-law’s iris garden. They are blooming wonderfully, but they are tipping over from being top heavy. Is there a solution to this problem? Both my neighbors are having the same problem. I want to make sure they are healthy because these bulbs hold a sentimental value for my wife. They are the offspring from her grandmother’s original iris garden. (e-mail reference)

A: When the blooms are large, heavy with dew or rainwater or a little weak from shade or nitrogen fertilization, it is necessary to stake them. I find that peony hoops work quite well on large clusters that tend to droop or use individual bamboo stakes for single plants. If they are in any significant shade, such as a half day, try to relocate them, after flowering, to a full-sun location.

Q: I salvaged some tulip bulbs that were going to be destroyed by a construction project. They were done blooming, but the leaves were still green. I dug as carefully as I could to keep the foliage, but don’t know what I should do with them now. Also, there were about a gazillion little
bulbs. Are they worth planting? I’ve never grown tulips before. (e-mail reference)

A: Yes, all are worth salvaging if you like tulips. The small ones eventually will flower for you once they get big enough. Get the tulips with foliage on them planted as soon as possible. They need to die down gradually to get carbohydrate storage built up again. If that happens, they will flower for you next year.

Q: I have two questions and I was told you where the best source for help. I have two lilac bushes that I think are Miss Kims. They flowered after they were planted, but it has been two years since they bloomed. They get enough sun. Someone told me I might have too much nitrogen in my soil. If it’s true, how do I get rid of it or is there another reason for the bushes not flowering? I have a snowball bush that is doing wonderfully. I think it is a viburnum plicatum (big white snowballs). The other day I noticed three huge suckers coming straight through the bush. The bush is young and very close to the ground. Should these suckers (if that is what they are) be clipped off or is it trying to make the bush taller and it should be left alone? When is the best time to prune and should I prune it well to encourage it to grow taller? (e-mail reference)

A: Lilacs fail to flower because of insufficient sunlight, planted too deeply, too much nitrogen, improper pruning or winterkill of the flower buds. You said the lilacs get plenty of sunlight, but unless you used a lawn fertilizer to provide nutrients, it isn’t likely too much nitrogen is the problem. If you planted too deeply, pull some of the soil back so the top of the roots are slightly exposed. If you pruned in July, then doing so removed the flower buds for the next growing season. If winter killed the flower buds, then hope for milder winters or purchase hardier lilacs.

In regards to your snowball bush, you have sucker growth coming from the rootstock. Prune it out immediately. Many viburnums are grafted on seedling rootstock that is not the same as the plant you want. Viburnums never should be shaped, so allow it to grow in its natural form. If they need pruning, do so by removing the oldest canes at the base to encourage new growth to thicken and develop the plant, but don’t do it often.

Q: I have an amaryllis plant that I put outside after it bloomed and took in again last fall. The blooms have faded, so I will cut off the blooms, but not the leaves. Can I harvest the seeds and produce new plants? If possible, I would like to try it! I think I see the seeds in pods by the withered blooms. (Moorhead, Minn.)

A: Yes, you can sow the seeds. They will germinate for you, if you don’t bury them too deeply. Barely cover the seeds. In addition, the mother bulb should be producing offshoot bulbs, so be sure to divide them and plant those as well. For the seed, expect it to take about five years to bloom. The offshoot bulbs will bloom in three years or less.

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Source: Ron Smith, (701) 231-8161, ronsmith@ndsuext.nodak.edu
Editor: Rich Mattern, (701) 231-6136, richard.mattern@ndsu.nodak.edu

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