Hortiscope

January 1, 2004

Hortiscope

Ronald C. Smith, Horticulturist
NDSU Extension Service

Q: I would like to know what to do with my rhubarb because it hasn't been doing too well. I don't want to transplant it, but I am wondering what kind of fertilizer I should use and when. (Roscoe, S.D.)

A: The fact that you are having a problem with your rhubarb is probably because it has been in one spot too long. When the leaf stalks don't attain the thickness you expect, that is usually the reason. The plants should be dug and divided every six to eight years to keep them vigorous.

You can try fertilizer; 10 10 10 using about a half cap per plant next spring, as new growth is just starting. That may be enough to pull them out of their funk.

Q: We have two garden plots and both have severe problems with blight. Potatoes are most affected though the tomatoes, beans and cucumbers have been hampered as well. We rotate what we plant, buy new seed and clean off old plants regularly. I sprayed the potatoes three times with fungicide but they were still greatly affected. Would leaving one plot idle next year and working it as a fallow help? Would it be helpful to plant a cover crop such as rye? (Tappen, N.D.)

A: Going fallow or with a rye cover for a year would help. So would three-year rotations away from anything in the tomato or potato family.

Q: I have a nice green lawn, but walking on it is like walking on a field of rocks. I've been told this is the work of night crawlers. Is there anything or any way to eliminate this problem? One suggestion was to aerate the lawn. Is that a remedy? (Cooperstown, N.D.)

A: Night crawlers are nature's roto tillers. They mix the thatch and subsoil as they do their burrowing. This is good for the turf but hard on the people who walk on it or try to mow it. Core aeration, power raking or rolling with a ballast roller will help but not eliminate the problem. There is no chemical registered for their control. It has been observed that where lawn care operators use a four step program of fertilizer, herbicide and insecticide on a regular basis, populations are much lower.

Q: Did you, this past summer, answer a question about putting pre emergent fertilizer on a newly seeded yard? Could you reprint the answer? (Frankfort, S.D.)

A: How I wish I was that organized! I get so many questions that I cannot specifically recall the one you're making reference to! But here is the low down on fertilizers for lawns. On new lawns, apply a starter material, which is higher in phosphorus and lower in nitrogen than normal.

For established lawns, do the spring fertilizer application around Memorial Day weekend. The fall application should be completed sometime around the Labor Day weekend. Do the winterizer application around Columbus Day.

Q: For the past two growing seasons my clematis has grown normally in the spring until it is about four feet tall. Then the lower leaves start to become mottled yellow. By July, the lower half of the vines have mottled leaves which then start to yellow completely, bleach out and finally turn brown. The plant is about five years old. It is growing on the south side of our shed and each spring is top dressed with composted sheep manure. Do you have any insight into what is causing these symptoms and how I can avoid them next year? (Bismarck, N.D.)

A: I really don't think your clematis has a disease problem. Your plant is having a physiological reaction to late summer stresses. Simply clean up the leaf litter and your plant should be okay next year.

Q: I have two questions about gardening. When is the best time to cut back peonies and how far from the ground? When should raspberry bushes be cut back and how far from the ground? (Aberdeen, S.D.)

A: Peonies can be cut back in late fall or early spring, before new growth emerges. Cut them as low as possible. Raspberries should have their fruit bearing canes cut back as soon as they have stopped bearing for the season. Some people wait until the following spring to do this, which is fine in most cases, but it is better to establish a habit of early cane removal. You want to do that because the old canes can be sources of disease and insect problems with next year's growth.

Generally, the canes that will bear fruit next year are cut to about breast height (four feet) in the early spring to facilitate easier harvesting.

Q: What is the name of the late blooming (October) flower that seems to thrive even when neglected? It is very stalk like with leaves coming out of the stem and the flowers are located on top. It doesn't seem to be a Shasta, Alaska or Nippon daisy. How can you tell the difference between small male and female cottonwoods and robust Siouxland varieties that are growing wild on Conservation Reserve Program land? I don't want the fuzz and would like to transplant some. (Fargo, N.D.)

A: I checked with my colleague Barb Laschkewitsch and in a heartbeat she said the flower you described was the herbstem giant white daisy. As far as the cottonwoods, there is no way of knowing the gender until they flower.

Q: I have a beta grape shrub that must be 20 to 25 years old. It has been producing grapes for several years. I have never trimmed it. If I do, what time of year should it be trimmed, how often and how much should be cut. (Portal, N.D.)

A: If you haven't pruned a grape vine in 20 or more years, I cannot begin to tell you how to prune it. I know I wouldn't want to! It should be done early in the spring when everything is still dormant.

Q: We have two apple trees that did bear well but half of the apples fell off of the trees before they were ripe. They weren't wormy but they did have black spots on them. We sprayed them but it did not help. Why did the apples fall off before they were ripe? They were on the green side but not too sweet. (Northville, S.D.)

A: Apple drop can be caused by environmental factors such as wind, moisture fluctuations, drought or early insect damage. The black specks you mentioned should not have caused the apples to fall early. That is simply cosmetic damage.

Q: I would like to plant wild fox grapevines to make into wine. Is there a domestic variety or can you get larger grapes from wild vines by pruning them? Where can I buy plants? We have a row of Lombardy poplar trees that need to be taken down because of age. I like the shade they give. Is there a better tree that is narrow and fast growing? Lombardy poplar seems to have a bad reputation. What about balleana poplar or a hybrid poplar screen variety? The trees will be planted in northeast South Dakota. (Elk River, Minn.)

A: I found the fox name under Vitis labrusea, which is also know as skunk grape or concord grape. I do not have a list of suppliers. The Lombardy poplars have a richly deserved bad reputation but I won't waste space discussing it. The upright European aspen, populus tremala erecta is a much better selection for our part of the country. Any other poplar would be better than the Lombardy.

Q: I noticed your article about how to crack black walnuts. I used to live in Ortonville, which is just across the state line from Big Stone. For 60 years I have cracked my black walnuts using a vise. It works great! You can crack and re crack to get the meat out. I agree that they are good in cookies and fudge. Black walnuts are few and far between up here. I used to get mine from the Twin Cities but my supply source has dried up. (Moorhead, Minn.)

A: Thanks for your tip on cracking black walnuts. I resisted the temptation to suggest placing them on a concrete driveway and backing over them with a pickup that has steel belted tires inflated to the maximum. Any way one can get at the nutmeat is worth it! I'll certainly let you and everyone else know if a new supply source comes to my attention.

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: Rich Mattern, (701) 231-6136, richard.mattern@ndsu.nodak.edu

North Dakota State University
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