Hortiscope

Ron Smith, Extension Horticulturist
North Dakota State University

Q: I have a number of Norwegian spruce that are growing tall and somewhat spindly. I have been told to cut the end growth of the branches and the tip to encourage branch growth, etc. Do you have information on this? (E-mail reference)

A: Yes, regular pruning will help to thicken up the form of these evergreens. It is best done in the early spring, clipping off soft new shoots to half their length to shape the growth. Spruce have multiple buds on their branches so the pruning doesn't have to be an exact science, as it is often done with a machete by commercial Christmas tree growers. Just be sure to NOT cut where there are no needles attached, as no new growth will result.

Q: Can you tell me how to control black spot in roses? (E-mail reference, Fargo, N.D.)

A: There are a couple of treatments that can be used for black spot control. The systemic fungicide Funginex will get into the plant and protect the new growth coming on, generally with a single application. Chlorothalonil is a contact fungicide that needs reapplication with the appearance of new growth. Generally the procedure for black spot control is to: 1) Clean up all fallen leaves. 2) Avoid overhead irrigation. 3) Avoid overfertilization. 4) Prune out all cankered canes. 5) Spray in spring while dormant with lime-sulfur. 6) Spray when new growth has emerged with Funginex or Chlorothalonil. 7) Give the roses an eastern exposure to help dry the foliage faster and help keep the spores from developing.

Q: When is the best time to dig up peonies to transplant them somewhere else? Also, when is the best time to transplant a bleeding heart? My peony had made seeds but I don't know if they are mature. They vary in color from very light tan to a black but they are all hard. If I plant these will they grow? (E-mail reference, Powers Lake, N.D.)

A: Peonies are best planted in the fall. The roots need time to establish before winter closes in, so if you can’t get it done between August and September you are better off delaying it until next fall. With the bleeding heart, you are better off waiting until spring just as new growth is emerging. Yes, eventually those seeds would become blooming peony plants. Sow them about an inch deep in the fall and water them in. You should see some young plants emerging the next spring, and in about three or so years have them blooming for you.

Q: In several of your answers on hydrangeas you state that they flower on current year growth, so people can prune them in the fall. This is not true. Only two species of hydrangeas flower on current growth, like the Annabelle and paniculata. The overwhelming majority of people grow H. macrophylla, which flowers on last year's growth. It will be severely affected by a late freeze or pruning. (E-mail reference)

A: You are right about the H. macrophylla- - the bigleaf hydrangea; it should be pruned right after flowering. If I lived in Georgia I would agree with you, this being a common selection for the south and coastal areas of the country. But, being in the Northern Plains I'll have to stick with what I have recommended, as the bigleaf hydrangea is not hardy in our area.

Q: I have an apple tree about 6 years old and it had nice apples on it for the first year. It is growing too tall and spindly, and I was wondering if I can cut the top and some of the upper branches off. Will it have apples next year? (Mercer, N.D.)

A: You bet! "Prune to harvest," I was told by an old orchardist when I was a kid. The best apples are always out of reach! Do so, however, in the early spring before leaf-out.

Q: I am writing for advice on slugs in my flowers. How do I get rid of them? (Sykeston, N.D)

A: There is "Slug-Getta," a bait that is effective; limestone powder spread over them will also do them in via dehydration and not harm the soil. Also, diatomaceous earth spread over their feeding area lacerates their soft bodies.

Q: I have an area that is mixed with clay and dirt. What can I do to loosen up the area? Should I add any fertilizer when I do it? (E-mail reference, Morris, Minn.)

A: The best solution to compaction is dilution with sphagnum peat moss. Work it in in the fall along with about 15 pounds of gypsum per 1000 square feet. This will improve the tilth or workability of your soil greatly.

Q: I have several amaryllis bulbs, some of which I've gotten to rebloom over the years. I put them outside all summer and fertilize, then stop watering and let the leaves fall off, then put them in the dark for several months. But this year, the leaves didn't drop off. Should I cut the leaves off and put the plants in the dark? Or just put them in the dark as is? Or what? (E-mail reference, Bismarck, N.D.)

A: I would suggest taking the amaryllis as is, and storing it in the dark. The fact that you've gotten some to rebloom is a credit to your green thumb. Keep up the good work!

Q: Can you tell me a natural way to stop potatoes from sprouting in storage? (E-mail reference)

A: My September 1995 copy of Organic Gardening, page 42, states, "Try putting some dried lavender, sage and rosemary in with your potatoes when storing them in a cool place. Researchers have found that oils in these herbs suppress sprouting and inhibit the growth of bacteria that can cause potatoes to rot in storage."

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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